Rozprawy doktorskie: „Estuarine fish”

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Mazumder, Debashish, i res cand@acu edu au. "Contribution of Saltmarsh to Temperate Estuarine Fish in Southeast Australia". Australian Catholic University. School of Arts and Science (NSW, 2004. http://dlibrary.acu.edu.au/digitaltheses/public/adt-acuvp47.09042006.

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Saltmarsh is an important coastal habitat located in the littoral zone of estuaries. Australian saltmarsh area is decreasing due to agricultural and urban development and invasion by mangrove. The aim of the study was to assess the contribution made by saltmarsh as a habitat and a source of food items for fish. Three saltmarsh sites were studied, with Towra Point chosen as a site for detailed ecological study. When corrected for water volume, fish densities were found to be higher within the saltmarsh compared to the adjacent mangrove. Although the fish assemblages in saltmarshes differed significantly from mangroves the overall ratio between commercially and ecologically valuable species in these habitats are similar, a result suggesting the importance of temperate saltmarsh as habitat for economically important fish. Significant export of crab larva from saltmarsh (average crab larval abundance 2124.63 m-3 outgoing water) is a positive contribution to the estuarine food chain supplementing the nutritional requirements of estuarine fish. While the diet of the crabs producing this larvae seems dependant on the saltmarsh environment (given the contrasting isotopic signatures of Sesarma erythrodactyla in saltmarsh and mangrove, and the similarity of isotopic signatures in the saltmarsh for Sesarma erythrodactyla and Helograpsus haswellianus), the crabs do not seem to be dependent on any of the common species of saltmarsh plant, but rather depend on particulate organic matter (POM) derived from local and other sources. Crab larva are a prey item for many estuarine fish, including commercially important species, as evidenced by gut content analysis of fish visiting the saltmarsh flats during spring tides. The results strongly suggest that emphasis be given to ecosystembased management for an estuary rather than component (e.g., vegetation) based managed as defined by the Fisheries Management Act (1994) and the State Environmental Planning Policy 14.

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Locascio, James Vincent. "Passive Acoustic Studies of Estuarine Fish Populations of Southwest Florida". Scholar Commons, 2010. https://scholarcommons.usf.edu/etd/1700.

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Recordings of fish sound production were made in Charlotte Harbor, Florida using Long Term Acoustic Recording Systems (LARS) programmed to record 10 seconds of sound every 10 minutes. Results demonstrated a strong circadian pattern in fish sound production that occurred within a few hours of dusk each evening. Sound production lasted on average 8.7 hrs each evening during the peak spawning season. LARS were deployed when Hurricane Charley crossed Charlotte Harbor in August, 2004. The hurricane did not inhibit nightly chorusing events of spawning fish. Rather, sound levels produced by spawning fish on the night of and 3 days after the hurricane were higher and lasted longer than any of the 9 days recorded prior to the hurricane. Acoustic time series data recorded at multiple sites in Charlotte Harbor during 2005 revealed changes in the spatial distribution of fish sound production in response to increased freshwater inflow and consequent decreased bottom dissolved oxygen concentrations in early June. Fish sound production decreased rapidly over several days at study sites in the northern portion of the harbor most immediately affected by changes in environmental conditions. Meanwhile, fish sound production increased at the study site furthest seaward where normoxic levels were sustained. By August levels of fresh water inflow decreased substantially, bottom dissolved oxygen levels increased and sound production resumed at sites previously affected by these conditions. Fish sound production began intermittently in February and ended in November. Peak levels were reached by mid-late April / early May and continued throughout the summer time. Seasonal patterns of sound production match the reported spawning periods of estuarine sciaenid species recorded. Black drum sound production was measured in the canal systems of Cape Coral and Punta Gorda, Florida during the 2004-2006 spawning seasons. The circadian pattern of sound production was similar to other sciaenids documented in Charlotte Harbor. Seasonal patterns of black drum sound production occurred during October through April and peaked in February. This seasonal period of sound production also matched patterns of black drum reproductive readiness and spawning reported in the literature for the Gulf of Mexico. A hydrophone array was used in the Cape Coral canal system to localize calling black drum and measure source levels and propagation of calls. Source level estimates averaged 165 dBRMS re: 1muPa SPL (SD=1.0) (n = 1,025). Call energy was concentrated in the fundamental frequency (94 Hz) and first two harmonics (188 Hz and 282 Hz). A square root model best described propagation of the fundamental frequency and first harmonic and a log 10 model best described the second harmonic. Based on the mean RMS source level, signal propagation, background levels, and hearing sensitivity, the communication range of black drum at the study site was estimated at between 33 and 108 meters and was limited by background levels, not auditory sensitivity. The timing and levels of sound production and egg production were compared in black drum. Eggs were collected hourly from 1800 - 0400 by surface plankton tows on two consecutive evenings while black drum sound production was continuously recorded. This sampling effort was conducted five separate times from January through April, 2006. Evidence of the time of spawning was indicated by the collection of blastodiscs (fertilized single cell eggs) or back calculated early cleavage stage eggs. Neither the timing nor the quantity of sound production was positively correlated with egg production on a nightly basis and the greatest densities of eggs were collected on evenings which had the lowest levels of sound production. This may have been due to differences in the fecundity of individual females spawning on the evenings when sampling was conducted.

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Jelbart, Jane E., University of Western Sydney, of Science Technology and Environment College i School of Environment and Agriculture. "The influence of seascape spatial features on the fish and macroinvertebrates in seagrass beds". THESIS_CSTE_EAG_Jelbert_J.xml, 2004. http://handle.uws.edu.au:8081/1959.7/492.

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Seagrass beds of Zostera capricorni are an integral part of the estuarine landscape along the east coast of Australia forming important habitats for juvenile fish and macroinvertebrates. Seagrass beds can vary in their spatial structural such as their size, shape and patchiness of seagrass cover. They can also be located within the estuarine landscape context such as their proximity to other habitats or their location within the estuary. The influence or correlation of these landscape or seascape spatial features of seagrass beds on the assemblages of seagrass fauna (fish and macroinvertebrates) was tested in this thesis. It was found that the spatial structure of seagrass beds (size and shape), their patchiness of the seagrass cover and location within the estuary (close or far from estuary mouth) were correlated with the assemblages of fish within seagrass beds. In particular it was demonstrated that there were greater densities of small fish species in the small compared to the large beds of Z. capricorni. This occurred regardless of the placement of the seagrass bed within the estuary context, its proximity to other habitats or patchiness of cover. Further experimentation using artificial seagrass patches demonstrated that this effect of patch size was independent of the perimeter length or perimeter to area ratio of the seagrass beds. It was hypothesised that the greater density of small fish species in small seagrass beds could be attributed to the greater proportion of edge habitats in small beds i.e. edge-mediated effects. However, the number of fish species per net haul in edges and inner regions of small and large seagrass beds were measured and found not to be different. The outcomes of this research suggest that to conserve the small fish species within an estuary, it is essential to protect even the small and patchy seagrass beds. A network of seagrass beds from all regions of the estuary is also required and the adjacent mangrove forests must be included
Doctor of Philosophy (PhD)

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Gill, Margaret Elizabeth. "Estuarine fish and their health, as indicators of anthropogenic change". Thesis, University of Newcastle Upon Tyne, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388651.

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Melville, Andrew J., i n/a. "Stable Isotope Tests of the Trophic Role of Estuarine Habitats for Fish". Griffith University. School of Environmental and Applied Science, 2005. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20060824.144508.

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The role of autotrophic production in different coastal habitats in the production of fish in estuaries is an important consideration in coastal management and conservation. In the estuarine waters of the Australian east coast, many economically important fish species occur over mudflats lacking conspicuous vegetation. I used stable isotope analysis to examine where such fish ultimately derived their nutrition, in the subtropical waters of southern Moreton Bay, Queensland, Australia. I first tested traditional processing methodologies of autotroph samples, in this case of mangrove leaves, and examined variability in mangrove isotope values at different spatial scales. Mangrove leaves processed using time-consuming grinding showed no significant difference in isotope values than coarsely broken leaf fragments. Isotope values of green leaves were not meaningfully different from yellow or brown leaves that would normally be the leaves that actually dropped on to the sediment. Future analyses therefore can use green leaves, since they are more abundant and therefore more easily collected, and can simply be processed as whole leaf fragments rather than being ground to a powder. Carbon and nitrogen isotope values varied at several spatial scales. The proportion of variability partitioned at different scales varied depending on the species of mangrove and element (C or N) analysed. To properly represent a geographic area, isotope analysis should be done on leaves collected at different locations and, especially, from different trees within locations. The autotrophic source(s) supporting food webs leading to fish production on mudflats might be either in situ microphytobenthos or material transported from adjacent habitats dominated by macrophytes. I tested the importance of these sources by measuring ?13C values of 22 fish species and six autotroph taxa (microphytobenthos on mudflats, and seagrass, seagrass epiphytic algae, mangroves, saltmarsh succulents and saltmarsh grass in adjacent habitats) in Moreton Bay. I calculated the distribution of feasible contributions of each autotroph to fishes. All fish ?13C values lay in the enriched half of the range for autotrophs. For over 90% of fishes, the top three contributing autotrophs were seagrass, epiphytes and saltmarsh grass, with median estimates of approximately 60-90% from these sources combined. Seagrass was typically ranked as the main contributor based on medians, while epiphytic algae stood out based on 75th percentile contributions. The other three sources, including MPB, were ranked in the top three contributors for only a single fish. Organic matter from seagrass meadows is clearly important at the base of food webs for fish on adjacent unvegetated mudflats, either through outwelling of particular organic matter or via a series of predator-prey interactions (trophic relay). Modelling results indicate that saltmarsh grass (Sporobolus) also had high contributions for many fish species, but this is probably a spurious result, reflecting the similarity in isotope values of this autotroph to seagrass. Carbon from adjacent habitats and not in situ microphytobenthos dominates the nutrition for this suite of 22 fishes caught over mudflats. The ultimate autotrophic sources supporting production of three commercially important fish species from Moreton Bay were re-examined by further analysing carbon and nitrogen stable isotope data. Mean isotope values over the whole estuary for fish and autotroph sources were again modelled to indicate feasible combinations of sources. Variability in isotope values among nine locations (separated by 3-10 km) was then used as a further test of the likelihood that sources were involved in fish nutrition. A positive spatial correlation between isotope values of a fish species and an autotroph indicates a substantial contribution from the autotroph. Spatial correlations were tested with a newly developed randomisation procedure using differences between fish and autotroph values at each location, based on carbon and nitrogen isotopes combined in two-dimensional space. Both whole estuary modelling and spatial analysis showed that seagrass, epiphytic algae and particulate organic matter in the water column, potentially including phytoplankton, are likely contributors to bream (Acanthopagrus australis) nutrition. However, spatial analysis also showed that mangroves were involved (up to 33% contribution), despite a very low contribution based on whole estuary modelling. Spatial analysis for sand whiting (Sillago ciliata) demonstrated the importance of two sources, mangroves and microalgae on the mudflats, considered unimportant based on whole estuary modelling. No spatial correlations were found between winter whiting (Sillago maculata) and autotrophs, either because fish moved among locations or relied on different autotrophs at different locations. Spatial correlations between consumer and source isotope values provide a useful analytical tool for identifying the role of autotrophs in foodwebs, and were used here to demonstrate that organic matter from adjacent habitats, and in some cases also in situ production of microalgae, were important to fish over mudflats. Whilst recognising that production from several habitats is implicated in the nutrition of fishes over mudflats in Moreton Bay, clearly the major source is from seagrass meadows. Organic matter deriving from seagrass itself and/or algae epiphytic on seagrass is the most important source at the base of fisheries food webs in Moreton Bay. The importance of seagrass and its epiphytic algae to production of fisheries species in Moreton Bay reinforces the need to conserve and protect seagrass meadows from adverse anthropogenic influences.

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Washburn, E. J. "Factors influencing salmonids use of an estuarine 'pool and weir' fish pass". Thesis, Swansea University, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.639353.

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The construction of a partial exclusion amenity barrage across the lower estuary of the River Tawe, South Wales, was completed in 1992. The structure includes a pool and weir fish pass consisting of 16 pools interlinked by deep notches in alternately downstream and cross facing traverses. Modifications to the fish pass weirs were carried out at the end of June 2000 in order to address the problem of excessive turbulence within the pools. The primary aim of this thesis was to examine the effectiveness of the modified fish pas under a range of environmental conditions. Underwater video was selected as the most suitable method for monitoring fish use of the pass and a system was designed and installed below the fish pass exit notch. The effects of time of day, tidal state, river flow volume and water quality on fish use of the modified pass were examined. Diel and tidal rhythms appeared to have the greatest impact on fish movements. The majority of fish exited the pass during daylight, supporting the hypothesis that fish utilise visual cues to negotiate obstacles. The timing of movement during tides which completely inundated the fish pass suggested that fish were using the rising tide to aid ascent, however a greater number of fish used the pass during non-inundating tides when this was main route past the barrage. Fish use of the pass appeared to be stimulated between river flows of 3.00 – 6.99 m³ s^-1 and 10 – 10.99 m³ s^-1, and there was evidence that salmonids use of the fish pass increased in response to changes in flow. Dissolved oxygen concentrations remained above levels which would affect the swimming ability of fish, although oxygen supersaturation may potentially cause periodic problems.

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Zagars, Matiss. "Estuarine mangrove fish communities in southwestern Thailand : trophic ecology and movement patterns". 京都大学 (Kyoto University), 2012. http://hdl.handle.net/2433/160976.

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Montoya-Maya, Phanor Hernando. "Dynamics of larval fish and zooplankton in selected south and west coast estuaries of South Africa". Thesis, Rhodes University, 2009. http://eprints.ru.ac.za/1641/.

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Markovsky, W. Coult. "The role of the Cape Fear River discharge plume in fisheries production : aggregation and trophic enhancement /". Electronic version (Microsoft Word), 2004. http://dl.uncw.edu/etd/2004/markovskyw/wcoultmarkovsky.doc.

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Bennett, B. A. "The utilization of littoral and estuarine habitats by fish in the Southwestern Cape". Doctoral thesis, University of Cape Town, 1989. http://hdl.handle.net/11427/8421.

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Includes bibliographies.
This thesis examines the utilization of rocky intertidal, sandy-beach surf-zone and estuarine habits by fishes on the southwestern Cape coast of South Africa. It has there central objectives: 1) to determine the species composition, abundance, size structure and seasonality of fish and to examine the extent to which they are influenced by environmental factors; 2) to describe the diets and patterns of feeding of the fish and to assess their impact on the food resources; and 3) to determine the importance of these habitats as nursery areas for juvenile fish.

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Cowley, Paul D. (Paul Denfer) 1964. "Fish population dynamics in a temporarily open/closed South African estuary". Thesis, Rhodes University, 1999. http://hdl.handle.net/10962/d1008543.

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The primary aim of this study was to investigate the population dynamics of the fishes associated with a small (17.5 hectares) temporarily open/closed estuary on the south east coast of South Africa. The results are based on the findings of an intensive sampling programme conducted over a period of four years in the East Kleinemonde estuary (33° 32' S : 27° 03' E). By adopting a quantitative approach, this study addresses the need for information on estuarine-associated fish population sizes, standing stock (biomass) estimates and productivity. The ichthyoplankton assemblage in the surf zone adjacent to the mouth of the estuary was dominated by postflexion larvae representing at least 21 taxa in 14 families. Rhabdosargus holubi of sizes ranging between 9 mm and 21 mm BL was the most abundant species with a mean density of 7.3 individuals per 100 m'. This species, which accounted for 77.6% of the catch composition, was recorded throughout the year but revealed a distinct peak in abundance in spring (August - September). The ichthyofaunal community within the East Kleinemonde estuary was dominated by juvenile marine-spawning species and typical of a warm temperate southern African estuary. A total of 30 species in 17 families was recorded, including the endangered estuarine pipefish Syngnathus watermeyeri. Multivariate analyses (classification and ordination) of the catch assemblages revealed a high degree of similarity (> 70%) throughout the estuary, with two distinct groups being identified on the basis of substratum type. The sampling stations near the mouth with a sandy substratum were distinguished from all other sampling sites in the estuary. The dominant estuarine-spawning species were represented by all life-history stages, suggesting that they bred successfully in the estuary. This group was numerically and gravimetrically dominated by the two zooplanktivorous shoaling species Gilchristella aestuaria and Atherina breviceps with density extrapolated population size estimates of 420 973 and 198 275 individuals, and biomass estimates of 1.6 and 0.6 g m⁻² respectively. The total population size of all estuarine-spawning species with a mean biomass 00.4 g m⁻² was estimated at 754 217 individuals. Population size estimates of the marine-spawning species were calculated using data obtained from three independent mark-recapture experiments. The assumptions for the mark-recapture analyses were adequately met and it was concluded that the techniques provided reliable estimates of population size. However, estimates obtained from density extrapolation revealed enormous variability and were considered to be unreliable. The total population size was estimated at 63 342, 18 592 and 13 5 192 during the three mark-recapture experiments respectively. The numerically dominant species during all three experiments was Rhabdosargus holubi. Biomass production of the marine-spawning species was evaluated over a 123 day census period when population sizes and estimates of growth rates were known. Productivity for all fishes with a standing stock of 26.2 g m⁻² was calculated at 4.5 g m⁻² month01 Rhabdosargus holubi accounted for more than 75% of the total marine fish productivity. This study draws attention to the success of Rhabdosargus holubi in the East Kleinemonde estuary, which is ascribed to aspects of its biology. These include an extended breeding season, the ability to recruit into the estuary under adverse open mouth conditions and its omnivorous food habits. The dominance of this migratory species suggests that it plays an important role in the transfer of energy to the coastal marine environment when the mouth of the East Kleinemonde estuary opens. Predation by birds and a dominant piscivorous fish (Lichia amia) was quantitatively assessed over a period of two years. Monthly food consumption by all piscivorous birds revealed large temporal variability, ranging from 32 to 466 kg month-I An unusual invasion of Cape cormorants during the winter of 1994 accounted for large scale mortality (2246 kg of fish) over a relatively short period. The predatory impact of this episodic event was reflected in the findings of the fish mark-recapture experiments, which revealed a 70% reduction in the total population of marine-spawning fishes (above a certain minimum size) in the estuary subsequent to this invasion. Monthly food consumption by the Lichia amia population in the estuary was calculated at 68 and 58 kg month-I for two distinct time periods when the population size was known. These findings suggest that this species is the top piscivorous predator in the East Kleinemonde estuary. Finally, the findings of this study highlight the temporal variability of fish populations within a single estuary. It is suggested that predation and estuary mouth conditions are the main factors influencing the abundance (and its variability) of individual species in the East Kleinemonde estuary.

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Sheppard, Jill Nicole. "Structure and functioning of fish assemblages in two South African estuaries, with emphasis on the presence and absence of aquatic macrophyte beds". Thesis, Rhodes University, 2010. http://hdl.handle.net/10962/d1005166.

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Temporarily open/closed estuaries (TOCEs) are the dominant estuary type in South Africa. These systems are often characterized by extensive beds of submerged macrophytes, which form important foraging and shelter habitats for fishes, especially for estuary-dependent fish species such as the Cape stumpnose Rhabdosargus holubi and Cape moony Monodactylus falciformis that are commonly associated with them. A loss of submerged macrophytes from an estuary has been shown to affect the fish community as well as reducing overall system productivity. The TOC East Kleinemonde Estuary, situated in the warm-temperate biogeographic region of South Africa has been subject to an ongoing long-term fish monitoring project since 1995. During the period 1995 to 2002, this estuary contained large beds of the submerged macrophytes Ruppia cirrhosa and Potamogeton pectinatus. However, subsequent to a major flood event in 2003 these macrophytes have been largely absent from this system. The effect of the loss of submerged macrophytes on the East Kleinemonde fish assemblage was investigated through an analysis of seine and gill net catch data. Seine net catches for a 12 year period, encompassing six years of macrophyte presence and six years of macrophyte senescence, revealed changes in the relative abundance of certain fish species. Vegetation-associated species such as R. holubi and M. falciformis decreased in abundance whereas sediment-associated species, especially members of the family Mugilidae, increased in abundance following loss of the macrophytes in this estuary. The critically endangered pipefish Syngnathus watermeyeri was only recorded in catches during years in which macrophyte beds were present. In addition to the analysis of catch data, the importance of macrophytes as a primary energy source for selected estuarine fishes was explored through the analysis of carbon and nitrogen stable isotopes. Prior to conducting these analyses, common methodological practices to address the presence of carbonates and lipids within isotope samples were evaluated. A subset of samples were either acid washed to remove carbonates, or lipids were removed according to the method of Bligh and Dyer (1959) as both of these compounds have been shown to affect stable carbon and nitrogen isotope ratios. The suitability of the lipid normalization models of Fry (2002) and Post et al. (2007) for samples of estuarine fish muscle were also tested. Based on this evaluation both models are suitable for use with estuarine fish muscle tissue, however since neither carbonate nor lipid content of any of the samples used in this study was high all samples were left untreated in the following analysis. Carbon isotope ratios from a wide range of fish species collected from the East Kleinemonde Estuary during the macrophyte-senescent phase were compared with individuals of the same species from the neighbouring West Kleinemonde Estuary (where extensive beds of R. cirrhosa and P. pectinatus were present) and revealed the influence of submerged macrophyte material in the diet of fishes in the latter system. However, it was apparent that these plants are not directly consumed but rather contribute to the detrital pool that forms a food source for most invertebrate and some fish species. The most significant source of carbon for East Kleinemonde fishes during the macrophyte senescent phase appeared to have a more depleted origin; probably from benthic or pelagic microalgae. In conclusion, while the importance of macrophyte beds as shelter and foraging habitats for estuarine fishes are well documented, their role in terms of the structuring and functioning of fish assemblages in TOCEs remains somewhat uncertain. The findings of this study were possibly masked by the resilience of vegetation-associated species to the loss of this habitat, as well as by life history characteristics of species such as R. holubi that allow their numerical dominance despite habitat change. Nonetheless, macrophyte senescence in the East Kleinemonde Estuary resulted in the loss of at least one species and the reduced abundance of vegetation-associated species, probably reflective of reduced food resources and/or increased vulnerability to predation. As a result, beds of submerged macrophytes are an important habitat within TOCEs.

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Branco, Paulo. "Conservation priority index for the portuguese estuarine fish species : Índice de prioridade de conservação para as espécies de peixes estuarinas portuguesas". Master's thesis, Universidade de Évora, 2008. http://hdl.handle.net/10174/18288.

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A consciência ambiental está a aumentar, sendo necessárias metodologias mais eficientes para determinar as prioridades de conservação de componentes biológicos. Os índices multimétricos são ferramentas importantes que permitem simplificar os dados, facilitando a sua compreensão por parte de gestores, decisores e do público em geral. O objectivo deste trabalho é formular um índice capaz de ordenar as espécies estuarinas portuguesas de peixes de acordo com a sua prioridade de conservação. Foram calculadas 1O métricas, com base em dados recolhidos na bibliografia, para 72 espécies de 16 sistemas estuarinos (costas O e S de Portugal). A validação do índice foi feita por meios externos. Este é o primeiro índice desenvolvido para avaliar a importância conservacionista de peixes estuarinos e permite identificar as espécies com maior e menor prioridade de conservação, auxiliando o planeamento da conservação de peixes estuarinos. ABSTRACT; Environmental awareness is increasing and more efficient methodologies in determining the conservation priorities of biological components are needed. Multimetric indices are important tools, allowing data simplification and consequently a better understanding by managers, decision makers and general public. The aim of this work is to formulate an index capable of ranking the Portuguese estuarine fish species by their conservation priority. Ten metrics were scored, with bibliography references, for 72 species of 16 estuarine systems (W and S coasts of Portugal). Index Validation was done by external means. This index is the first to specifically address the conservation priority of estuarine fish and allows an identification of the top and bottom conservation priority species adding thus the planning of estuarine fish conservation. // Public awareness regarding environmental issues has been increasing in the last decades. The increasing number of impact assessment studies, management and conservation plans, as well as ecological monitoring studies, demand new and more efficient techniques. Indices are an important tool aiding biologists in studies and allowing an easier comprehension of the data by managers, decision makers and general public. This study presents the first multimetrical index for establishing a hierarchical ordination of the conservation priority of estuarine fish species using, for that, 72 species from 16 estuarine systems (W and S coasts of Portugal). The index is composed by ten metrics, comprising species' life traits, and distribution and population trends. The information needed to score each metric was gathered from bibliography and the index validation was done by external means. This methodology allowed the defmition of the fish species more in need of conservation planning, and those less prone to extinction in estuarine systems. The proposed index will fill a gap in the knowledge and contributes with a useful tool to the scientific community and to the decision makers, being a breakthrough on estuarine fish species conservation planning.

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Richardson, Naomi. "A preliminary investigation into the use of biomarkers and a fish community index to assess estuarine health in selected Eastern Cape estuaries". Thesis, Rhodes University, 2008. http://hdl.handle.net/10962/d1007480.

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The aims of this study were to determine the potential use of biomarkers at multiple levels of biological organisation together with a fish community bioindicator to assess the estuarine health status of three temporarily open/closed estuaries. The estuaries investigated were the East Kleinemonde (EK), Old Woman's (OW) and Mtana (MTN), all of which are situated in the Eastern Cape Province. Three biomarkers, the acetylcholinesterase (AChE) assay, lipid peroxidation (LPx) assay, liver histopathology and a condition factor were used to determine sub-organism health and one bioindicator, the Estuarine Fish Community Index (EFCI), was used as a bioindicator of community health. The estuarine-dependent marine species Rhabdosargus holubi was selected as an indicator species for the sub-organism level analyses. The results from the community analyses indicated that the EK and OW estuaries were in 'good' condition, while the MTN was found to be in 'moderate' condition. Histological analyses revealed that R. holubi from all three estuaries showed signs of pathological changes to the liver, with the fish from the MTN eliciting the highest occurrence of these changes. The LPx assay found that R. holubi from both the OW and MTN showed signs of oxidative damage in the liver tissue, but those from the EK did not appear to be affected. The AChE assay showed that only the fish from the OW had been affected by anticholinesterase compounds. A laboratory study was undertaken using R. holubi as a positive control for the AChE and LPx assay. The fish were exposed to 3 μg/L chlorpyrifos, a known cholinesterase inhibitor, for six hours and their tissues were examined for changes to LPx levels and AChE activities. AChE activity was significantly inhibited (Mann Whitney U test, Z = 3.65, n = 38, P < 0.001) by the exposure, but LPx levels were not significantly affected. A composite index incorporating the biomarkers at different biological levels of organisation was developed. The index was designed to assist managers and scientists to determine whether the ichthyofauna of a system was being affected by environmental stressors and what management interventions could be undertaken to ameliorate the water quality in an estuary. The index was applied to the three estuaries investigated during the present study and both the OW and MTN were assessed to be in need of immediate management intervention. The fish in the OW were found to be stressed at all the sub-organism levels measured and the reason for this was hypothesised to be as a result of golf course activities in this adjacent estuary. A number of management actions are proposed to reduce the sub-organism stress observed in the fish from the OW. The livers of fish from the MTN were shown to be under stress; however the causative agent of this stress was unknown because there is no formal development in the MTN catchment. However, a possible contaminant source is proposed and management interventions to alleviate the stress on the biota of the MTN are suggested. The EK does not require immediate management intervention, however, continuous routine monitoring is recommended to ensure that conditions do not deteriorate. Shortcomings of the index were outlined and a number of suggestions were made in terms of other measures of biological health which could be incorporated into the index.

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Branson, Adam. "A comparison of fish assemblages utilizing estuarine and ocean surf habitats in southeastern North Carolina". View electronic thesis (PDF), 2009. http://dl.uncw.edu/etd/2009-2/bransona/adambranson.pdf.

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Pham, Cong Tri. "The ecology of fish larvae in Pumicestone Passage : an estuarine system in Southeast Queensland, Australia /". St. Lucia, Qld, 2000. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16437.pdf.

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Childs, Amber-Robyn, Paul D. (Paul Denfer) 1964 Cowley, T. F. Næsje, Anthony John Booth, E. B. Thorstad i F. Økland. "Do environmental factors influence the movement of estuarine fish? A case study using acoustic telemetry". Estuarine, Coastal and Shelf Science, 2008. http://hdl.handle.net/10962/d1008070.

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Telemetry methods were used to investigate the influence of selected environmental variables on the position and movement of an estuarine-dependent haemulid, the spotted grunter Pomadasys commersonnii (Lacepède 1801), in the Great Fish Estuary, South Africa. Forty individuals (263–698 mm TL) were surgically implanted with acoustic coded transmitters and manually tracked during two periods (7 February to 24 March 2003; n = 20 and 29 September to 15 November 2003; n = 20). Real-time data revealed that spotted grunter are euryhaline (0–37) and are able to tolerate large variations in turbidity (4–356 FTU) and temperature (16–30 °C). However, the fish altered their position in response to large fluctuations in salinity, temperature and turbidity, which are characteristic of tidal estuarine environments. Furthermore, tidal phase had a strong influence on the position of spotted grunter in the estuary.

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18

Sutherland, Kate. "The dynamics of Larval fish and Zooplankton assemblages in the Sundays Estuary, South Africa". Thesis, Nelson Mandela Metropolitan University, 2010. http://hdl.handle.net/10948/1119.

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The larval fish and zooplankton assemblages were studied in the permanently open Sundays Estuary on the south-east coast of South Africa, using standard boat-based plankton towing methods. A total of 8174 larval and early juvenile fishes were caught, representing 12 families and 23 taxa. The Clupeidae, Gobiidae and Blenniidae were the dominant fish families. Common species included Gilchristella aestuaria, Caffrogobius gilchristi, Omobranchus woodi, Liza dumerilii, Glossogobius callidus and Myxus capensis. Estuarine resident species (Category I) predominantly in the preflexion developmental stage, dominated the system. A total of 19 zooplankton taxa were recorded. Copepoda dominated the zooplankton community. Dominant species included Pseudodiaptomus hessei, Acartia longipatella, Halicyclops sp., Mesopodopsis wooldridgei, and the larvae of Paratylodiplax edwardsii and Hymenosoma orbiculare. Mean larval fish density showed similar trends seasonally, spatially and across salinity zones, with mean zooplankton density in the Sundays Estuary. Gut content analysis of five larval fish species: Gilchristella aestuaria, Pomadasys commersonnii, Monodactylus falciformis, Myxus capensis and Rhabdosargus holubi, revealed species specific diet and prey selection. Although larval fish diet contained a variety of prey items, guts were dominated by P. hessei, chironomid larvae, Corophium triaenonyx, copepod eggs and insect larvae. Physico-chemical drivers and the interactions between these two plankton communities provide information that enables a more holistic view of the dynamics occurring in the Sundays Estuary planktonic ecosystem.

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19

Norton, Olivia Bridget. "The population structure of two estuarine fish species, atherina breviceps (Pisces: Atherinidae) and gilchristella aestuaria (Pisces: Clupeidae), along the Southern African coastline". Thesis, Rhodes University, 2006. http://hdl.handle.net/10962/d1005431.

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Phylogeographic patterns of coastal organisms with different life histories and breeding strategies may reveal patterns not consistent with the current delineation of the biogeographic provinces around South Africa. The subdivision of the South African coastline into these three main climatological or biogeographic regions: namely the cool temperate west coast, the warm temperate south coast and the subtropical east coast, is based on average seawater temperatures and hydrological conditions. Genealogies of two estuarine fish species Atherina breviceps, a marine breeder, and Gilchristella aestuaria, an estuarine spawner, were reconstructed using mitochondrial DNA (mtDNA) control region sequences. The study comprised two components, an assessment of a small dataset of both fish species to compare their population structure along the South African coastline and a more comprehensive investigation of the phylogeography of G. aestuaria collected from 21 estuaries around the coast. The comparative study of A. breviceps and G. aestuaria indicate different population distribution patterns along the South African coastline. Results of the A. breviceps analysis demonstrate substantial gene flow due to the random mixing of alleles, while the comparative G. aestuaria dataset indicates a more structured population and considerably less gene flow. The G. aestuaria population demonstrates geographic separation into four groups, namely the west coast (Great Berg), Bot (south coast), Seekoei (south coast) and east coast (Bushmans, Kasouga and Cefane). Results from the larger G. aestuaria dataset indicate that the phylogeographic patterns observed during this study do not conform to existing biogeographic boundaries along the southern African coastline. The delineation identified during this study between the warm temperate and subtropical regions is further south than originally perceived and this southward extension can be ascribed to the prevailing hydrology. The life history patterns and ecology of these two estuarine fish species appears key to understanding their population structure. These factors interact with environmental characteristics such as physical oceanography and the distribution of estuaries (along the coastline) to explain the observed distribution patterns and population structure of A. breviceps and G. aestuaria.

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Cochran, Maria Karin. "Uptake Routes of Benzo[a]pyrene in an Estuarine Killifish: Cytochrome P4501A Immunohistochemistry using Whole Fish". W&M ScholarWorks, 1994. https://scholarworks.wm.edu/etd/1539617672.

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Santos, Paulo Roberto Santos dos. "A pesca artesanal da Miragaia (Pogonias cromis, Scieanidae) e consequências da sobreexplotação, no estuário da Lagoa dos Patos". reponame:Repositório Institucional da FURG, 2015. http://repositorio.furg.br/handle/1/6060.

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O aumento na abundância de peixes não residentes da zona estuarina, atraem o interesse da frota pesqueira, que atua sobre os estoques de forma intensa, muitas vezes levando a sobreexplotação. No estuário da Lagoa dos Patos, a Miragaia (Pogonias cromis), é um peixe estuarino dependente que por muitos anos foi um importante recurso pesqueiro, e hoje encontra-se sobreexplotado e ameaçado de extinção. As capturas que atingiram 1400 t em 1976, decaíram posteriormente e foram inexistentes nos anos de 2004, 2005, 2008, 2009 e 2010. Mas recentemente, se observa o aumento dos desembarques na região. A partir disso, a presente dissertação tem por objetivo descrever a pesca artesanal da Miragaia no estuário da Lagoa dos Patos e analisar o efeito da sobreexplotação no ciclo reprodutivo da população remanescente na região. No primeiro capítulo intitulado "A pesca artesanal da Miragaia (Pogonias cromis, Scieanidae) no estuário da Lagoa dos Patos", é discutida a hipótese de que os maiores valores de esforço e CPUE são encontrados no mesmo período de maior abundância da espécie no estuário, e verifica-se a influência do esforço de pesca nas variações da CPUE. De forma complementar, se confirma a distinta composição dos desembarques entre o período de desova e o resto do ano, a predominância de adultos no período de desova evidencia o aumento da abundância. No segundo capítulo intitulado "O efeito da sobreexplotação no ciclo reprodutivo da Miragaia (Pogonias cromis, Scieanidae)" é discutido a redução da idade e tamanho de primeira maturação sexual e consequentemente fecundidade dos exemplares, como consequência da sobrepesca sofrida pela espécie em anos anteriores. Os resultados encontrados mostram a situação preocupante da população de Miragaias no estuário da Lagoa dos Patos, onde a manutenção da intensidade pesqueira pode levar ao colapso da atividade e posterior extinção local da espécie.
The increase in the abundance of non-resident fish estuarine zone attract the interest of the fishing fleet, which operates on the intensely stocks, often leading to overexploitation. In the estuary of Patos Lagoon, the Black drum (Pogonias cromis) is an estuarine-dependent fish who for many years was an important fishing resource, and today is overexploited and threatened with extinction. Catches reached 1400 t in 1976, declined later and were negligible in the years 2004, 2005, 2008, 2009 and 2010. But recently observed increased landings in the region. Thus, this thesis aims to describe artisanal fishing of Black drum in the estuary of Patos Lagoon and analyze the effect of v overexploitation in the reproductive cycle of the remaining population in the region. In the first chapter entitled "The artisanal fishery Black drum (Pogonias cromis, Scieanidae) in the estuary of Patos Lagoon," discusses the hypothesis that higher values of effort and CPUE are found in the same period of greatest abundance of the species in the estuary, and there is the influence of fishing effort in changes in CPUE in a complementary way confirms the different composition of landings spawning periods for the rest of the year, the prevalence of adults in spawning highlights the increasing abundance. In the second chapter entitled "The effect of overexploitation in the reproductive cycle of Black drum (Pogonias cromis, Scieanidae)" is discussed reducing the age and size at first sexual maturity and consequently fertility of copies as a result of overfishing suffered by the species in previous years. The results show the worrying situation of the population of Black drum in the estuary of Patos Lagoon, where the maintenance of fishing intensity can lead to the collapse of activity and subsequent local extinction of the species.

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Islam, Md Shahidul. "Feeding ecology of continental relict fish juveniles associated with Chikugo estuarine turbidity maximum in Ariake Bay, Japan". Kyoto University, 2006. http://hdl.handle.net/2433/144099.

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Kyoto University (京都大学)
0048
新制・課程博士
博士(農学)
甲第12362号
農博第1543号
新制||農||924(附属図書館)
学位論文||H18||N4120(農学部図書室)
24198
UT51-2006-J354
京都大学大学院農学研究科応用生物科学専攻
(主査)教授田中克, 教授藤原建紀, 教授山下洋
学位規則第4条第1項該当

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23

Levasseur, Maurice. "Phytoplankton dynamics and the distribution of fish larvae and their nutritional resources across an estuarine plume front". Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/30589.

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In the marine environment, export production leading to the traditional food chain is a relatively rare event taking place primarily in hydrographic features such as frontal areas. When export production persists, massive reproduction of herbivores is expected to occur. Since copepod eggs and nauplii are the main prey of a majority of fish postlarvae, the spawning of dominant fish species is expected to be associated with fronts. The aims of this study were to determine the influence of an estuarine plume front upon the phytoplankton dynamics (distribution and physiological status) and to assess the role of the cross-frontal circulation upon the distribution of fish larvae and their prey. The frontal area under study is located in the northwestern part of the Gulf of St. Lawrence, at the interface between a coastal jet (Gaspe Current) flowing along the Gaspe Peninsula and the Anticosti Gyre. In early June, maximum phytoplankton concentrations (up to 35 μg chl a L⁻¹) were found in the Gaspe Current. In the salinity gradient, a significant correlation was found between salinity and phytoplankton concentrations (and seston in general), indicating that physical processes (vertical and horizontal mixing) were more important in controlling the seston distribution than biological processes. The dominance of physical processes is probably due to the high current velocities and shear stress in the Gaspe Current in early June. Later during the season, the cross-frontal mixing was less vigorous due to the lower freshwater runoff, and the front acted as a retention zone for estuarine plankton. Maximum diatom concentrations (up to 50 μg chl a L⁻¹) were measured in the front per se. Measurements of nitrogen and silicate concentrations (ambient and intracellular) and uptake rates suggested that silicate generally limited diatom growth across the front. In June, estuarine larvae (capelin, Mallotus villosus and sand lance, Ammodytes hexapterus) were concentrated in the diatom-rich Gaspe Current and front where immature copepod stages were abundant. The five-fold increase in immature copepod concentrations between the gyre and the current/front resulted probably from a food-induced increase in copepod reproduction. Thus it appears that the dispersion strategy of the estuarine species in relation with local hydrography favours the exploitation of the resource-rich Gaspe current and front by the first-feeding postlarvae. The extrusion of redfish (Sebastes spp.) larvae appears to be synchronized with the copepod reproduction that followed the gyre April/May bloom. Later, redfish larvae were also found in abundance in the resource-rich front.
Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate

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24

James, Nicola Caroline. "Trends in fish community structure and recruitment in a temporarily open/closed South African estuary". Thesis, Rhodes University, 2007. http://hdl.handle.net/10962/d1005178.

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Long-term interannual changes in richness, abundance, diversity and structure of the fish community in the temporarily open/closed East Kleinemonde Estuary, Eastern Cape, are described and the recruitment success of two estuary-dependent marine species assessed. In addition, laboratory experiments were conducted to assess the possible role of olfaction in the recruitment process of an estuary-dependent marine fish species. Multivariate analyses of the annual marine fish communites identified two distinct groups with more species recorded during years that succeeded spring (September to November) mouth opening events than in years following no mouth opening events in spring. Interannual community stability (IMD) and seriation (IMS) also increased from the ‘other’ to the ‘spring’ years. These results highlight the importance of the timing of mouth opening to the marine fish community in a temporarily open/closed estuary. This study also made use of long-term records of daily mouth state and linked them to the recruitment of distinct year-class cohorts in two spardis with contrasting lifehistory characteristics. Lithognathus lithognathus only recruited into the estuary in years when the mouth opened between late August and January. This was linked to the limited spawning season of this species and its inability to enter closed estuaries via wave overwash events. In contrast, recruitment by Rhabdosargus holubi juveniles appeared to be uninterrupted and was not determined by the seasonality of mouth opening. This species dominates the marine-spawning component of the East Kleinemonde Estuary and its success is attributed to an extended spawning season and its ability to recruit into estuaries during both overwash and open mouth conditions. Attraction of postflexion Rhabdosargus holubi larvae to estuary, surf zone and river water was also measured using a rectangular choice chamber. In two sets of experiments, conducted during peak recruitment periods, larvae from both the surf zone and estuary mouth region selected estuary water with a significantly higher frequency than sea water. Larvae collected in the mouth region showed a stronger preference for river water than those collected in the surf zone, thus suggesting that these fish are more attracted to freshwater influenced nursery areas once they have entered the estuary than those in the surf zone. Larvae collected in the marine environment also selected surf zone water with significantly higher frequencies than estuary water or offshore sea water, thus confirming the importance of the surf zone as an interim nursery area for postflexion R. holubi.

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Hossain, Md Mustafa Kamal, i res cand@acu edu au. "An Examination of Seagrass Monitoring Protocols as Applied to Two New South Wales Estuarine Settings". Australian Catholic University. School of Arts and Sciences (NSW), 2005. http://dlibrary.acu.edu.au/digitaltheses/public/adt-acuvp81.25092005.

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Many recent studies have sought to monitor health characteristics of seagrasses, including changes in aerial extent, biomass and fish community structure. While these studies have provided important information on the ecology of seagrass communities on southeast Australia, little attempt has been made to subject these sampling procedures to rigorous experimental testing and review. This study employed commonly-used standard methods for sampling seagrass community characteristics in two sites in New South Wales. Where possible, sampling protocols were tested for accuracy and efficiency at a range of temporal and spatial scales. The ARCView Geographic Information System was used to construct vegetation polygons of seagrass distribution on the Tweed River, and in the Ukerebagh Channel annually over a 5-year period. For one year (2000), distributions from identical photographs were mapped twice to identify procedural errors. In general, errors relating to incorrect boundary identification were low compared to inter-annual variability. Inter-annual variability in seagrass beds was higher than for adjacent mangrove and saltmarsh. Estimates of biomass were derived from standard replicate 0.25m x 0.25m quadrats. The experiment contrasted two sites of similar geomorphic setting. Ukerebagh Channel on the Tweed River, and Woolooware Bay with Botany Bay are both shallow, sandy marine deltaic settings supporting stands of Zostera capricorni. Significant differences were found in the degree of replication required to identify significant changes in seagrass biomass at the two sites. Ukerebagh Channel supported relatively dense stands of Z. capricorni with low intra-site variability. Here 8 replicates were sufficient to detect 10 percent change. Towra Point presented a contrast, in which 15 replicates were required to detect a similar level of change. Woolooware Bay at Towra Point has suffered from increased sedimentation relating to alterations in current velocities at Towra Point, and the result highlights the greater degree of replication required to determine significance changes in disturbed systems. The fish populations in the seagrass at Towra Point were sampled using buoyant pop nets. Fish communities differed significantly from those sampled in adjacent mangrove and saltmarsh. Differences in fish assemblages between spring high tides, neap high tides and low tides are attributed to movements of fish between seagrass and adjacent mangrove and saltmarsh. This mosaic of habitats is utilized by a number of species over a tidal cycle, with seagrass providing an important low-tide refuge for many species utilizing mangrove and saltmarsh at high tide. Limitations in the efficiency of buoyant pop nets were exposed in a novel experiment which demonstrated differences in escape rates between species. Flat-tailed mullet (Liza argenta) are likely to be under-represented in experiments using this technique. Recommendations are made regarding optimal sampling protocols for monitoring seagrass in the region. All techniques tested are suitable, though some require modification. Some texts have under-estimated the degree of replication required to appropriately monitor changes in seagrass biomass in disturbed systems, where density is lower and intra-site variability higher. The buoyant pop-nets may require modification in open-water seagrass situations where escape by Liza argenta and Acanthopagrus australis were at unacceptable levels.

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Harrison, Trevor D. "Biogeography and community structure of fishes in South African estuaries". Thesis, Rhodes University, 2003. http://hdl.handle.net/10962/d1005078.

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The biogeography and community structure of the fishes of South African estuaries was investigated. In all, 109 systems were examined representing two broad types: temporarily closed and permanently open estuaries. Multivariate analyses of the fish communities identified three biogeographic regions. A cool-temperate region extended along the west and southwest coasts; a warmtemperate zone stretched along the south, southeast and east coasts and a subtropical region occurred along the east coast. The boundaries of these biogeographic regions were also delineated. The general physico-chemical characteristics of the estuaries within the three biogeographic regions also reflected regional differences in climate, rainfall and ocean conditions. Estuarine temperatures followed the trend for marine coastal waters, decreasing from subtropical estuaries toward cool-temperate systems. The low rainfall and runoff in the warm-temperate region together with high evaporation rates and strong seawater input resulted in higher salinities in these estuaries. These factors also accounted for the predominantly clearer waters in warm-temperate estuaries. The estuaries in the three biogeographic regions were also shown to contain somewhat distinctive fish assemblages. Temperature and salinity appeared to be the two main factors affecting the distribution and abundance of fishes in South African estuaries. Subtropical systems were characterised by fishes mostly of tropical origin as well as certain south coast endemic species. Warm-temperate estuaries were dominated by endemic taxa with some tropical species also present. The fish fauna of cooltemperate estuaries mostly comprised south coast endemic species with cosmopolitan and temperate taxa also present. Certain functional components of the ichthyofauna also exhibited slight differences between regions. Freshwater fishes were a major component of closed subtropical estuaries while estuarine resident species were more abundant in warm-temperate estuaries. Overall, estuarine-dependent marine species dominated the fish fauna of the estuaries in all biogeographic regions, signifying that South African estuaries perform a vital nursery function for this group of fishes. Slight differences were also apparent in the trophic structure of the fishes; these were related to environmental differences between regions. Zooplanktivores and fishes that feed on aquatic macrophytes/invertebrates assumed a relatively higher importance in warm-temperate systems. Overall, detritivores dominated the estuarine fish fauna in all regions, indicating that detritus forms the main energy source in South African estuaries.

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Brady, Damian C. "Behavior of juvenile estuary-dependent fish in relation to the spatial and temporal dynamics of diel-cycling hypoxia in an estuarine tributary". Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 346 p, 2008. http://proquest.umi.com/pqdweb?did=1609283451&sid=4&Fmt=2&clientId=8331&RQT=309&VName=PQD.

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28

Lamberth, Stephen Justin. "Approaches to assessing the status of nearshore and estuarine fish and fisheries and their responses to environmental change". Doctoral thesis, University of Cape Town, 2008. http://hdl.handle.net/11427/6118.

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Includes bibliographical references (leaves 163-180).
In multispecies fisheries knowledge, personnel and funding limitations often create the dilemma over which species should be the first to receive management and research attention. This thesis uses a Multi-Criteria Decision Analysis approach to prioritize 176 South African linefish species on the basis of a number of criteria indicating conservation and socio-economic importance. Each species importance was assessed from the points of view of (1) conservation, (2) each fishery sector separately and combined and (3) the overall combined conservation and sectorial importance. Relative scores within each of the fishery sectors were dominated by two or three species such that the scores separating the remaining species from each other were small. On the whole, the top species included those most important in each sector, biogeographic region and in terms of conservation. The separate and overall ran kings should assist in the development of broadly acceptable management strategies for different fish. Catch data for 129 of 255 functional estuaries on the South African coastline were reviewed and the relationships between fish catch and estuarine size, type and biogeographical region analysed using simple and multivariate models. Estuary size alone explained over 80% of the variation in catch in the warm temperate region and over 90% of the variation in catch in the cool temperate and subtropical region. Further analysis of the two main estuarine types (permanently open and temporarily open/closed estuaries) revealed higher productivity for the permanently open systems. Both estuarine size (ha) and type (5 types) were used to explain catches using general linear models. The models were able to explain 82-98% of the variance in catches. The total estuarine catch in South Africa was estimated at 2 480 tons per annum with a total value of R748 million, of which 99% could be attributed to recreational angling. Estuarine contribution to the inshore marine fisheries was estimated at approximately R846 million per year with estuarine dependent species comprising 83% of the catch of the recreational shore and commercial seine and gillnet fisheries and only 7% of the catch of the recreational spearfishery and commercial and recreational boat fisheries. Total value of estuarine and estuary-dependent fisheries was estimated to be R1.594 billion per annum in 2008 rands. The cool-temperate Olifants and warm temperate Breede estuaries on the west and south coasts of South Africa have both seen a >35% reduction in mean annual runoff (MAR) from a historical reference condition to the present day with a >60% reduction possible under future development. With almost no exceptions, the Olifants Estuary fish assemblage has seen an overall 20% decrease in abundance from reference to the present day and will gradually decline to 55% of reference with a predicted future 60% reduction in MAR. Consequently, future reductions in flow are likely to see the Olifants Estuary progressing towards a low biomass, low diversity, marine-dominated system. In contrast, with the exception of some key exploited species, fish abundance in the Breede Estuary has increased by 6% from reference to the present day and is likely to increase to 115% of reference with future reductions in flow. In all, the fish assemblage will experience a gradual change from a relatively high-diversity low-abundance freshwater-rich system under historical flow conditions to a high-diversity, highabundance, marine-dominated system with future reductions in flow.

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Claus, Sonia Carmel, University of Western Sydney, of Science Technology and Environment College i of Science Food and Horticulture School. "Heavy metals in biota from temperate Australian estuaries". THESIS_CSTE_SFH_Claus_S.xml, 2003. http://handle.uws.edu.au:8081/1959.7/503.

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The detection of anthropogenic impacts in our estuaries has become a critical social, political and scientific concern in recent years. Work has focussed on the effects of these impacts on the spatial and temporal patterns of biotic assemblages and searched for bioindicators and biomarkers of pollutants that may act as early warning signs. The estuaries in temperate Southeastern Australia have a diversity of biotic assemblages living in the soft sediment. One of the most abundant macroinvertebrates is the little studies mussel, Xenostrobus securi that is found living with an assemblage of benthic biota including amphipods, crabs, isopods and tanaids, bivalves and gastropods. Two commercial fish species bream and mullet also inhabit these estuaries. Numerous stormwater drains can be found entering the estuaries through the mangrove forests lining the shores. Along with inputs of freshwater, stormwater drains are thought to be responsible for the entry of heavy metals into estuaries. These heavy metals have the potential to alter the patterns of biotic assemblages and bioaccumulate in the tissues of miacroinvertebrates, mussels and fish living within temperate estuaries. Over the time of this study the concentrations of heavy metals in the sediment tissues and shell of X.Securis varies spatially and temporally. Although this study adds substantially to current knowledge there is still more that is needed to establish X. Securis as a bioindicator. Questions remain about uptake, depuration and response to environmental gradients of heavy metals in X. Securis. Before X Securis can be used routinely in monitoring heavy metal contamination these questions need to be further investigated
Doctor of Philosophy (PhD)

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30

Muller, Cuen. "Evaluating the importance of mangroves as fish nurseries in selected warm temperate South African estuaries". Thesis, Nelson Mandela Metropolitan University, 2017. http://hdl.handle.net/10948/12080.

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The value of mangrove habitats as fish nurseries was assessed by comparing communities of early stage and juvenile fishes between estuaries with and without mangroves. Early stage fishes were sampled using boat-based plankton towing while juveniles were sampled by seine netting. Sampling took place at five sites spaced 1 km apart starting near the estuary mouth in four estuaries along the temperate coastline of the Eastern Cape Province of South Africa. Four estuaries were selected based on shared similarities which included catchment area, estuarine area and shared habitats barring the presence of mangroves which occupied the river margins of two systems. Results revealed that early stage and juvenile fish communities (both marine- and estuary-spawned) were similar between systems with and without mangrove habitats. Differences in fish communities among estuaries were rather attributed to axial salinity gradients associated with greater freshwater input, while season and temperature produced significant variances in fish densities with Generalised Additive Models revealing responses of communities to these variables. A common estuarine-dependent fish, Rhabdosargus holubi (Family Sparidae), was further investigated to determine habitat use, residency and dietary patterns in different mangrove habitats. High habitat residency in this species was revealed during a short-term tagging study using Visible Implant Elastomer tags and long-term isotope analysis in juveniles sampled from two contrasting mangrove habitats. A wider feeding niche was observed in an eelgrass-red mangrove connected habitat when compared with more exposed white mangrove areas. Low dependence on mangrove habitats in temperate estuaries is likely due to their tidally dominated inundation and limited refuge potential due to smaller area coverage by mangroves in temperate estuaries. Relatively lower primary productivity in warm temperate mangrove areas, relative to their tropical counterparts, provides no significant feeding advantage or refuge opportunities relative to other available habitats in these estuaries. Warm temperate estuaries, which are both spatially and temporally highly variable, instead host species which are habitat generalists, able to capitalise on these highly dynamic environments.

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Midgley, Craig. "Trends in the fish assemblage structure of two South African transition-zone estuaries : can these trends be linked to climate change?" Thesis, Rhodes University, 2014. http://hdl.handle.net/10962/d1013173.

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Changes in the fish communities of the Breede and Mbashe estuaries were investigated in relation to the environmental variables that influence the fish assemblages in these systems. The Breede Estuary (34° 24’21.6”S, 20° 51’ 08.2”E) occurs within the warm-temperate/cool-temperate transition-zone, while the Mbashe Estuary (32o 14' 55.4"S, 28o 54' 03.7"E) falls within the subtropical/warm-temperate transition-zone along the South African coastline. The Breede Estuary was sampled (seine and gill nets) during summer (January-March) over a period of 10 years (2002-2012), while the Mbashe Estuary was sampled (seine net) during spring (October) over a period of three years (2010-2012). The proportion of tropical fish species was higher in the Mbashe Estuary compared to the Breede Estuary, while the Breede Estuary contained a higher proportion of temperate species than the Mbashe Estuary. Although the abundance of individual species in both estuaries varied, the ranking of species in the Breede Estuary was stable over the 10 year period. Multivariate analysis showed that the fish communities within each reach (upper, middle, lower) of the Breede Estuary remained similar, regardless of year. In contrast, species composition in the Mbashe Estuary differed significantly between years mainly due to differences in the river flow regime during the study period. Environmental variables responsible for structuring the fish assemblage in each estuary differed. Salinity significantly impacted the spatial fish assemblage structure of the Breede Estuary, with most of the species recorded being associated with the more saline lower reaches. The abundance of tropical species near their distributional limit in the Breede Estuary appeared to be impacted by sea surface temperature (SST) as peak total abundance of these species coincided with the warmest SST, while the lowest total abundance coincided with the coldest annual SST during the study period. The fish assemblage structure in the Mbashe Estuary was impacted by differing freshwater input prior to sampling, with flooding negatively impacting the mean total abundance, species composition and diversity in this system. The variables that influenced the fish assemblage structure of both transition-zone estuaries will be affected by climate change in the future. These variables will, in turn, determine the composition, abundance and diversity of species within these important estuarine systems. In order to measure these impacts with any degree of understanding, long-term studies on the abiotic and biotic (including the ichthyofauna) features of these estuaries are required to interpret climate change trends.

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Claus, Sonia Carmel. "Heavy metals in biota from temperate Australian estuaries /". View thesis, 2003. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20051013.092820/index.html.

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Thesis (Ph.D.) -- University of Western Sydney, 2003.
"Submitted in fulfilment of the requirements for the degree of Doctor of Philosophy at the University of Western Sydney Hawlesbury" Bibliography : leaves 245-278.

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33

Grant, Walter Lawrence. "The community structure and feeding ecology of the ichthyofauna in the Mngazana and Mngazi estuaries, Port St. Johns, South Africa". Thesis, Nelson Mandela Metropolitan University, 2007. http://hdl.handle.net/10948/513.

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The Mngazana and Mngazi estuaries are situated just south of Port St. Johns close to the biogeographical boundary between the warm temperate and subtropical zones along the east coast of Southern Africa. The Mngazana estuary is a permanently open estuary with three species of mangrove. The Mngazi estuary is a temporarily open/closed system. The ichthyofauna was sampled with seine nets and gillnets during June 2005, August 2005, November 2005, February 2006 and April 2006. The fish community structure was significantly different between the two estuaries with the differences being especially noticeable in the larger fish sampled with gillnets. There were significant differences in the fish community sampled with the seine net on both spatial and temporal scales in both of the estuaries. Certain warm temperate species were less abundant and certain subtropical species were more abundant at the Mngazana estuary than they were during a study conducted in 1975. Stomach content analysis revealed that most species had similar diets in the two estuaries with the only differences occurring among benthic feeding species. The diet of sub-adult piscivores comprised of a large proportion of penaeid prawns while the juveniles feed mainly on mysids. The zooplanktivorous fish feed mainly on copepods and mysids with the proportions varying between the species. Benthic feeding fishes showed the greatest variability in diet with plant material, detritus, crabs and copepods being the main food sources. Stable isotopes revealed that particulate organic matter and microphytobenthos were the most important carbon sources to fish in the Mngazi estuary. In the Mngazana estuary a combination of mangrove material, detritus, particulate organic matter and Zostera material were the most important carbon sources. The importance of each of these sources did, however, vary greatly between the different trophic guilds of the fish in the Mngazana estuary. The distribution of certain fish species was investigated in relation to physical parameters (temperature, salinity, turbidity and depth) and biological parameters (prey and predators) in the environment. It was found that most small fish (< 100 mm SL) were strongly correlated with turbidity where-as they showed weak correlations with their prey. Sub-adult piscivores fell into two groups, i.e. those that could tolerate turbid water and those that were only found in clear water. The group that also occurred in turbid water showed very strong correlations with their prey but the clear water group did not. It would appear that the small and thus vulnerable fish seemed to occur in areas that offered them protection rather than areas where their food supply is most abundant, where-as the piscivores were more influenced by prey distribution, as long as the physical conditions were tolerable to them.

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Lounder, Cecelia. "Recruitment dynamics and otolith chemical signatures of juvenile gray snapper, Lutjanus griseus, among West Florida estuarine and coastal marine ecosystems". [Pensacola, Fla.] : University of West Florida, 2009. http://purl.fcla.edu/fcla/etd/WFE0000156.

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Boehme-Terrana, Linae Marie. "Trace metals and stable isotopes as tracers of life history and trophic connections in estuarine-dependent fish from Tampa Bay, Florida". [Tampa, Fla.] : University of South Florida, 2007. http://purl.fcla.edu/usf/dc/et/SFE0002241.

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Brito, Pâmella Silva de. "ESTRUTURA DE COMUNIDADE DOS PEIXES ASSOCIADOS A PRADOS DE FANERÓGAMAS MARINHAS DA ILHA DO MARANHÃO". Universidade Federal do Maranhão, 2014. http://tedebc.ufma.br:8080/jspui/handle/tede/528.

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Made available in DSpace on 2016-08-17T15:00:40Z (GMT). No. of bitstreams: 1 Dissertacao - PamellaSilvaBrito.pdf: 2572284 bytes, checksum: 775b92e1aa430b94c10075867a76b869 (MD5) Previous issue date: 2014-08-29
FUNDAÇÃO DE AMPARO À PESQUISA E AO DESENVOLVIMENTO CIENTIFICO E TECNOLÓGICO DO MARANHÃO
The marine phanerogams meadows are important because they are nursery areas for many species of fish. In order to describe the community structure, temporal and spatial patterns of fish using Spartina alterniflora meadows of Maranhão Island present in tide macro region were held six samples of nine points in the period between July 2012 and June 2013, using a trawl net. A total of 11,660 individuals captured, representing 80 species, in which 13 are new record for the state of Maranhao. The sampled points are represented by a few abundant species (Rhinosardinia bahiensis, Atherinella brasiliensis, Lycengraulis grossidens, Lycengraulis batesii, incilis Mugil and Centegraulis edentulus) that demonstrated use the space according to interspecific preferences and presenting distribution patterns with the occurrence of distributed Juveniles throughout the year, suggesting that the studied environments are used by many species such as nursery areas and these have food preferences for zooplankton and mostly characterized as marine fish that frequent the estuary at some period of their life cycle. The species A. brasiliensis was constant in the spatial and temporal distribution, L. batesii was more abundant in the dry and the species L. grossidens, M. incilis, R. bahiensis, C. edentulus were dominant in the rainy season. The abiotic factors did not change much numerically, being only significant for dissolved oxygen between stations and different salinity for locations. We can see the meadows shown to be constant in the temporal variation and differed between sites, which showed no significant differences between the evaluation variables. Thus we can infer that the studied phytal environment is considered a nursery, it is frequented by several species of mostly juvenile fish that use this area as a place of recruitment, food and shelter; the dynamics of patches of seagrass were stable during the dry and rainy seasons and the composition and abundance of fish community is more explained by the spatial dynamics, but still have temporal distribution patterns, these features are typical of tropical environments that are inserted in mosaic adjacent environments.
Os prados de fanerógamas marinhas são importantes por serem áreas de berçário de muitas espécies de peixes. A fim de descrever a estrutura da comunidade, padrões temporais e espaciais de peixes que utilizam prados de Spartina alterniflora da Ilha do Maranhão, presentes em região de macromarés foram realizadas seis amostragens de nove pontos no período entre Julho de 2012 e junho de 2013, utilizando uma rede de arrasto. Um total de 11.660 indivíduos capturados, correspondendo a 80 espécies, na qual 13 são nova ocorrência para o estado do Maranhão. Os pontos amostrados são representados por algumas espécies abundantes (Rhinosardinia bahiensis, Atherinella brasiliensis, Lycengraulis grossidens, Lycengraulis batesii, Mugil incilis e Centegraulis edentulus) que demonstraram utilizar o espaço de acordo com preferências interespecíficas e apresentando padrões de distribuição com a ocorrência dos indivíduos juvenis distribuída durante todo o ano, sugerindo que os ambientes estudados são utilizados por várias espécies como áreas de berçário e estas apresentam preferências alimentar por zooplancton em sua maioria e caracterizadas como peixes marinhos que frequentam o estuário em algum período do seu ciclo de vida. A espécie A. brasiliensis mostrou-se constante na distribuição espacial e temporal, L. batesii foi mais abundante na seca e as espécies L. grossidens, M. incilis, R. bahiensis, C. edentulus foram dominantes no período chuvoso. Os fatores abióticos não variaram muito numericamente, apenas sendo significante para oxigênio dissolvido entre as estações e salinidade diferente para locais. Podemos observar os prados mostraram-se constantes na variação temporal e diferiu entre os locais, os quais não apresentaram variações significativas entre as variáveis de avaliação. Dessa maneira podemos inferir que o ambiente fital estudado é considerado um berçário, pois é frequentado por várias espécies de peixes principalmente juvenis que utilizam essa área como local de recrutamento, alimentação e refúgio; a dinâmica dos prados de fanerógamas se mantiveram estáveis durante os períodos seco e chuvoso e que a composição e abundância da comunidade de peixes é mais explicada pela dinâmica espacial, mas ainda assim possuem padrões de distribuição temporal, essas características são típicas de ambientes tropicais que estão inseridos em mosaico de ambientes adjacentes.

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37

Cole, Russell Gavin. "Distributional relationships among subtidal algae, sea urchins and reef fish in northeastern New Zealand". Thesis, University of Auckland, 1993. http://hdl.handle.net/2292/1912.

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Interactions among large brown macroalgae, sea urchins, and fishes were investigated in northeastern New Zealand during the period 1988 - 1993. The Cape Rodney to Okakari Point Marine Reserve was the site of many of these investigations. The patterns of abundance of large brown macroalgae and urchins down depth gradients over a wide geographic range were compared with those reported from earlier studies, and 3 major trends were identified. First, the fucoid alga Carpophyllum flexuosum now occurs at many sites which are exposed to wave action, in contrast to earlier studies. This alga occurred most abundantly on urchin-grazed coralline flat areas. Second, at four sites in the Marine Reserve, the densities of the echinometrid urchin Evechinus chloroticus decreased with increasing depth, rather than reaching maximal densities at mid-depths, as had previously been described. Finally, at sites of decreased exposure to wave action, the coralline flats habitat did not occur at all, and dense stands of. C. flexuosum occurred, in conjunction with the ubiquitous laminarian alga, Ecklonia radiata. Following the discovery of this new algal component to exposed rocky reefs, a more detailed study of its population characteristics was initiated. The population size structure of C. flexuosum on coralline flat areas was markedly different from that of the same species in sites sheltered from wave action. These differences occurred at both offshore islands and sites near Leigh, suggesting that it was a general pattern. C. flexuosum plants on coralline flats were smaller than those from sheltered sites, and had a greater number of smaller laminae, heavier stipes, and a greater degree of branching. There was some evidence of temporal change in the morphology of C. flexuosum from coralline flats. Comparisons between a site with C. flexuosum and a site with coralline flats suggested that the activity of fish was 75% lower in the vegetated than in the unvegetated site, and the feeding rate in the vegetated site was less than 50% that in the unvegetated site. I speculate that future effects on fish activity of the invasion of C. flexuosum into a habitat which previously lacked macroalgal vegetation may depend on changes in the morphology of plants. An investigation of many aspects of the biology of E. chloroticus in different habitats was undertaken. Analysis of the body dimensions of E. chloroticus suggested that this species was relatively tall compared to other echinometrids (average ratio of test height: test diameter = 0.54), Comparisons among habitats with differing amounts of vegetation revealed only small differences in the relationship between test diameter and test height. Small E. chloroticus (<40 mm test diameter) lived in crevices, while larger individuals grazed freely over the substratum. In vegetated habitats, the crevice-dwelling habit was maintained at test diameters about l0 mm greater than in unvegetated habitats. Very small (<20 mm test diameter) E. chloroticus frequently covered themselves with shell. Population size structures of E. chloroticus within the Cape Rodney to Okakari Point Marine Reserve were bimodal; other localities had unimodal populations. Modal sizes varied among localities, with smallest modes (50-60 mm TD) being found at Inner Hauraki Gulf sites, and largest modes at the offshore Mokohinau Islands (70-80 mm TD). Habitat did not predictably affect population size structure. A bimodal population structure was maintained at Waterfall Reef rock flats throughout the 5-year study period. Gonad size showed seasonal fluctuations at several sites, being greatest in summer. There were few consistent differences in gonad size between biological habitats. Gonad colour varied among sites and habitats, with orange gonads generally being more prevalent in vegetated habitats, and black gonads being represented more in unvegetated habitats. Smaller urchins had greater proportions of orange gonads, while larger urchins had greater proportions of brown and black gonads. Although highly variable among individual urchins, movement of E. chloroticus was greater at unvegetated sites (0.7 m per 5 days) than at vegetated sites (0.4 m per 5 days), in the Marine Reserve. Feeding of E. chloroticus was studied at a number of sites in the Marine Reserve. Urchins frequently consumed drift algae, particularly E. radiata. C. flexuosum was consumed at less than half the rate of other macroalgae in several laboratory feeding experiments, and was chosen least frequently in a field assay of feeding preferences among 8 species of macroalgae. Boosting densities of E. chloroticus in stands of E. radiata to 60 m-2 led to destructive grazing of plants over a 2 month period - at lower densities, the urchins dispersed. Densities of C. flexuosum were effectively unchanged when urchin densities were increased to these elevated levels. As a result of these observations I speculate that feeding preferences of E. chloroticus may have a role in allowing C. flexuosum to survive on coralline flats. In a laboratory experiment, urchins from a feeding aggregation did not graze algae at higher rates than individuals from outside aggregations. Diets of both E. radiata and C. flexuosum consistently produced similar gonad volumes in urchins held in the laboratory, although gonad volumes produced were low. A preliminary experiment suggested that C. flexuosum from exposed sites was consumed at lower rates than C. flexuosum from sites which were sheltered from wave action. These differences in palatability are mirrored in the formation of stable borders between coralline flats and C. flexuosum of the sheltered morphology, and the ability of C. flexuosum of the exposed morphology to survive in the coralline flats habitat. The fish fauna of the Cape Rodney to Okakari Point Marine Reserve was shown to be different from that of a nearby area. A number of species were more abundant within the Marine Reserve. Subsequent surveys showed that there were differences in abundances of 3 large carnivorous fishes among sites within the Marine Reserve, and that population size structure and the distance within which divers could approach one species, (Pagrus auratus), clearly varied between areas within the Marine Reserve. Mean standard length of P. auratus in the central marine reserve was 40% larger than that of P. auratus outside the central marine reserve, and the average minimum approach distance was 70% less in the central marine reserve. Feeding of fish by humans in the central part of the Marine Reserve was suggested to be the main cause of the differences in responses to divers. Population size structure of, and crevice occupancy by, E. chloroticus, clearly differed between the Marine Reserve and an adjacent area, with bimodal population size structures and a 10 mm greater size of crevice occupancy occurring in the Marine Reserve. The implications of these findings for extrapolating from experiments done in one area to other areas are discussed. The major biological components of rocky reef habitats identified in this study were broadly similar to those identified in previous studies in northeastern New Zealand, and have parallels in overseas studies. Long term changes to the flora of rocky reefs in northeastern New Zealand have occurred, and appear to persist by a mechanism which had previously been discounted. Similar processes to those observed in overseas studies appear to maintain habitats (consistent recruitment of algae or urchins to habitats which they dominate), or cause them to change from one habitat state to another (e.g. grazing outbreaks by urchins). However, the predictability of the persistence of these habitats at a particular site appears to be low. Further, the precise mechanisms whereby habitats may change from one to another may also be unpredictable. I argue that there is little scope for general statements concerning the spatial and temporal occurrence, or mode, of habitat transitions on temperate subtidal reefs. This study emphasises the value of repeated descriptions of patterns of abundance, and highlights problems of extrapolation and generalisation in marine ecology. Insufficient information exists at present to comment adequately on the persistence of subtidal habitat types. This may in part stem from the types of information which have been collected in the past. Methodological problems with the use of quadrats to sample densities of organisms in areas of differing topography are therefore addressed. In conclusion, it is suggested that sampling protocols which incorporate a variety of information, gathered over as wide an area, and as intensively as possible, should be used in future research of this type.

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Magoro, Mandla Leon. "Predation by alien largemouth bass, Micropterus salmoides Lacepéde 1802 (Centrarchidae: Perciformes), on indigenous marine fish species in the Kowie System, South Africa". Thesis, Rhodes University, 2014. http://hdl.handle.net/10962/d1011939.

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Estuaries serve as nursery areas for a large number of estuary-associated fish species. Some of these taxa also use river catchments as nursery areas. During the upstream migration of this latter group, the juveniles are prone to predation by native and alien predatory fish inhabiting the system. The rate of invasion of ecosystems by alien organisms can be directly linked to anthropogenic influences, including both intentional and unintentional introductions by alien organisms into new regions. The largemouth bass, Micropterus salmoides, is a facultative piscivorous fish that has been successfully introduced worldwide for the main purpose of sport fishing. Where introduced, it has been found to negatively impact native fish and invertebrate species through predation, competitive exclusion and displacement of indigenous fish species. The aim of this thesis was to investigate the predatory impact of largemouth bass on the estuary-associated Cape moony Monodactylus falciformis, Cape stumpnose Rhabdosargus holubi and freshwater mullet Myxus capensis in the lower Kowie River of the Eastern Cape Province, South Africa. A combination of approaches was employed during this study. Stomach contents, stable isotopes and fatty acid analyses were employed for the reconstruction of the diet of largemouth bass. Acoustic telemetry was used to elucidate largemouth bass movements, particularly their ability to enter the upper reaches of the Kowie Estuary. Stomach contents and stable isotopes analyses showed that M. salmoides exhibit an ontogenic shift in diet, with small and medium sized individuals consuming the higher proportion of fish prey, while large sized individuals mostly consumed invertebrates such as crabs (Potamonautes sidneyi) and Odonata larvae, while consuming only a small proportion of estuary-associated fish. Fatty acid analysis only showed a direct connection between the fatty acid profiles of largemouth bass and those of M. capensis and M. falciformis. The acoustic telemetry results indicated that some M. salmoides individuals periodically move into the upper reaches of the estuary following river flood events. The results obtained from all these approaches highlight the risk posed by largemouth bass introductions on indigenous fish species, particularly those that enter the areas occupied by these top predators.

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Nguyen, Xuan Tong, Thi Thu Huong Tran, Thi Thuy Duong, Huong Mai, Trong Khang Duong, Cong Luc Huynh, Thi Loan Pham i Thi Phuong Quynh Le. "Bioaccumulation of organochlorine pesticides (OCPs) in molluscs and fish at the Sai Gon - Dong Nai estuary". Technische Universität Dresden, 2018. https://tud.qucosa.de/id/qucosa%3A33295.

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The aim of this study is to assess the biological accumulation of pesticide residues in aquatic organisms in Sai Gon - Dong Nai (SG-DN) estuary. Fish and mollusks were collected directly at the Soai Rap and Long Tau estuary of the SG-DN river system, washed and separated for taking the tissue. The organochlorine compounds from the tissue were then extracted and analyzed by gas chromatography system. The results showed that, the concentration of OCPs in Tegillarca granosa, Meretrix lyrata, Margaritifera auricularia and Bostrychus sinensis varied from 6.4 to 59.9 μg/kg, 7.2 to 322 μg/kg, 4.5 to 62.1 μg/kg and 2.9 to 114.3 μg/kg fresh weight, respectively. In general, molluscs species that accumulate more heptachlor, aldrin, endrin or dieldrin tend to accumulate less DDT (dichlorodiphenyltrichloroethane). Endosulfan was the most commonly found in three bivalve mollusks while DDTs (1.5–75.2 μg/kg, averaging 8.7 μg/kg weight) was the most popular OCPs in the fish (Bostrychus sinensis) samples. In DDT group, the p,p’-DDT metabolite accounted for the largest percentage, reaching 50% of total DDTs. In HCH (Hexachlorocyclohexane) group, β-HCH isomer was predominant in almost samples.
Mgr đích ccc nghiên cch này là đánh giá tích lũy sinh hhn ccn thuu trr sâu trong các sinh vvn ssnh dưưh nưưh ttư khu vvu ccu sông Sài Gòn - ĐĐn Nai (SG-DN). Cá và nhuyyu thh đưưy llư trry tiiy iicửa sông Soài RRà và Lòng Tàu thuu hh thhu sông SG-DN, đư-D rư- ss-D và tách llc phhh mô thht. Các hhc chh clo hho cơ sau đó đưưđ tách chii và phân tích bbch hh thhh ssh ký khí. Kết quả nghiên cứu cho thấy, dư lượng OCPs tích tụ trong sò điệp (Tegillarca granosa), ngao (Meretrix lyrata), trai nước ngọt (Margaritifera auricularia) và cá bớp (Bostrychus sinensis) dao động tương ứng từ 6,4 đến 59,9 μg/kg, 7,2 đến 322 μg/kg, 4,5 đến 62,1 μg/kg và 2,9 đến 114,3 μg/kg trọng lượng tươi. Nhìn chung, loài nhuyễn thể nào tích lũy nhiều heptachlor, aldrin, endrin hoăc dieldrin có xu hướng tích lũy ít DDT (Dichlorodiphenyltrichloroethane). Endosunfan là nhóm thuốc được tìm thấy nhiều nhất trong các loài nhuyễn thể nghiên cứu. Ngược lại, nhóm DDT lại phổ biến ở cá Bostrychus sinensis (1.5–75.2 μg/kg, trung bình 8.7 μg/kg trọng lượng). Dạng p.p’-DDT trong nhóm DDT chiếm tỷ lệ cao nhất, tới 50% DDT tổng. Trong khi đó, đồng dạng β-HCH của nhóm HCH (Hexachlorocyclohexane) chiếm đa số trong hầu hết các mẫu.

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40

Vieira, Joao P. "Ecology of estuarine fish assemblages in Patos Lagoon, Brazil (32 degrees S), and York River, USA (37 degrees N), with review of zoogeography of fishes in western Atlantic warm-temperate and tropical estuaries". W&M ScholarWorks, 1991. https://scholarworks.wm.edu/etd/1539616892.

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The first two chapters of this study examine faunal composition and latitudinal patterns in diversity of fishes in warm-temperate and tropical estuarine waters of the western Atlantic from La Plata River (35&\sp\circ&S), Argentina, to Chesapeake Bay (37&\sp\circ&N), USA (33 faunal reports). Species distributions generally corresponded with previously recognized marine zoogeographic regions, and cluster analyses also showed that faunal similarity among estuarine sampling sites was related to the type of sampling gear used and to the type of habitat that was sampled in each estuary. The total number of fish species reported is positively related to the size of the area sampled and number of individuals collected, although latitude (or temperature related phenomena) played a critical role in determining richness and equitability among species. The results of this study show that interaction between disturbance frequency or magnitude (e.g. temperature and salinity variations) and the rate at which dominance is achieved can result in a predictable pattern of fish species diversity in estuaries. In the last chapter the structure of estuarine fish assemblages in Patos Lagoon (32&\sp\circ&S), Brazil, and York River (37&\sp\circ&N), USA is described using historical bottom trawl data, to examine similarities between geographically isolated fish assemblages. Within broad limits structural assemblage patterns were correlated with temperature changes, although the intensity of seasonal changes differed between them. The lowest winter temperatures in the York River were correlated with a pronounced seasonal species emigration from the estuary, a pattern which was not observed in the more thermally moderate Patos Lagoon. Patos Lagoon was more diverse in terms of equitability and species richness than the York River at any particular point in time, but the seasonal pattern of use of the estuary (i.e. nursery and feeding grounds) was similar between localities, and did not differ from other temperate or tropical estuaries. Comparing fish assemblages using a nondimensional diversity index (i.e, H&\sp\prime&) masks interesting differences in species richness and relative abundance, and measurements of species richness and equitability (rarefaction and relative species rank techniques) independent of sample size should be used in order to determine richness and equitability differences among systems.

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Kerr, Melissa L. "The Ability of an Aquatic Invader to Uptake Nutrients in an Upstream Estuarine Environment: Implications for Reducing the Intensity and Frequency of Massive Fish Kills in Florida". Scholar Commons, 2017. http://scholarcommons.usf.edu/etd/6878.

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The purpose of this study was to assess whether nutrient absorption rates by water hyacinths are affected by low-salinity levels. In a controlled experiment, water hyacinths demonstrated the ability to absorb a significant amount of nutrients in low-saline waters while maintaining a slowed growth rate and shortened life span. Nutrient rates were reduced by an average of 36% in ammonia nitrogen and 48% in reactive phosphorus in the tanks of 4.45 parts per thousand (ppt) salinity. Growth rate in the experimental tanks of 4.45 ppt was observed at 33% slower than that of the control. The high salinity comparison tank of 7.0 ppt experienced complete mortality after three days. Phytoremediation practices through the use of an aquatic invader, water hyacinths, can be used to reduce large-scale fish kills along the eastern U.S.’s major estuarine systems, focusing on Florida’s waters. Toxic dinoflagellates and other harmful algal blooms have been plaguing the contributing waterways of North Carolina and the Chesapeake Bay and are the main causes of these massive fish kills. The characteristics and trends that these upstream estuarine systems are following could serve as a warning for Florida. An analysis of Florida’s fish kill database, as well as patterns and trends of the fish kills in North Carolina and the Chesapeake Bay, were used to determine areas at an increased risk for toxic dinoflagellates and harmful algal blooms to occur. Areas are proposed for water hyacinths to be implemented in a controlled method to reduce massive fish kills in Florida’s waters.

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Olds, Alexis Amy. "The ichthyofauna of the Wilderness Lakes System, Western Cape, with particular emphasis on alien fish species and their establishment success". Thesis, Rhodes University, 2012. http://hdl.handle.net/10962/d1005132.

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Freshwater fish species have been introduced into freshwater systems around the world, primarily for aquaculture, ornamental fish trade and sport fishing. Their introduction into estuarine systems is uncommon however, instances do occur and their establishment success and impacts on these estuarine systems is not well documented. The extent of invasion by four freshwater fishes in a RAMSAR listed estuarine system, the Wilderness Lakes, Western Cape was investigated. This thesis determined the relative abundance and distribution of alien fishes in relation to the native fish biota, their establishment success in the system, what factors inhibited their establishment and whether the introduction of alien fishes negatively impacted the native fish biota. The distribution and abundance of fishes were assessed primarily using fyke nets, seine nets and gill nets in each of the lakes, interconnecting channels and the Touw Estuary. The fish fauna was made up of euryhaline marine species comprising 46%, native estuarine species comprising 18%, catadromous species comprising 7% and freshwater alien species comprising 29% of the total biomass sampled. A total of 26 species were sampled in the system, three of which were considered alien; Oreochromis mossambicus, Gambusia affinis and Cyprinus carpio, and Micropterus salmoides were not sampled but confirmed in the system. Establishment success was determined by evidence of: a sustainable breeding population, a wide distribution, abundant in the sampling area, and all size classes of fish sampled. Gambusia affinis and Oreochromis mossambicus have been recorded in the system for a minimum of 13 and 26 years respectively. They were widely distributed and highly abundant and are established in the system. Micropterus salmoides was first recorded in the system in 1985 but abundances have remained low with fish appearing to be limited to Island Lake and Langvlei. Reproduction appeared to be limited by higher salinity and these factors indicated that this was a casual species which relies on repeated introductions for population maintenance. Cyprinus carpio spawned successfully in 2010 and was widely distributed but abundances were still low with a total of 15 fish being sampled throughout the system, and was thus in the establishing phase. As these are considered freshwater alien species, the physico-chemical parameters in the estuarine environment inhibiting the establishment success of the alien fishes were investigated. Gambusia affinis and O. mossambicus were not limited by the physical environment, and while O. mossambicus cannot tolerate temperatures below 11⁰C, temperatures only dropped below its tolerance for a total of two days between February 2010 and February 2011. Cyprinus carpio and M. salmoides were restricted by salinity in Rondevlei and Langvlei but could tolerate salinity in Island Lake and the Touw Estuary during closed mouth phases. While adults appeared to tolerate the salinity in the system, egg and larval development could be affected thus reducing the viability of the population. The abundance of alien fishes did not negatively impact the abundance of native fish species. The interactions between the native and alien fish biota tended towards biotic acceptance where, as alien abundance increased so did native fish abundance. The impacts of the alien fishes on the native fish biota were assessed by comparing the fish community from a study completed in 1985 to the findings of this study. From these two studies there were no apparent negative impacts on the native fish biota and the fish community composition would most likely be structured by estuarine mouth opening events.

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Stein, William III. "Fish and decapod community structure in estuarine habitats of the New Orleans Land Bridge, including a description of the life cycle of tarpon (Megalops atlanticus) in southeastern Louisiana". ScholarWorks@UNO, 2013. http://scholarworks.uno.edu/td/1673.

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Estuarine marshes are generally considered to be productive but not necessarily diverse ecosystems. During 24 consecutive months, I collected 65,000 fishes and decapods comprising over 65 species from the New Orleans Land Bridge, an estuarine salt marsh. My research details the distribution of nekton across five contiguous but geomorphically different regions, which I defined as “Areas”. This factor “Area” was significant in explaining community composition differences in 11 of the 24 months I evaluated. That is, during those 11 months community structure was different among the Areas. Specific “month” was also found to be a significant factor as community structure was found to differ among the months. No consistent abiotic factors were associated with community structure. These observations imply that a different set of factors are associated with community structure at the Area level than at the microhabitat level. Sampling of nekton in shallow estuarine salt marsh habitats was difficult. The cast net is a useful gear type for this type of sampling and can be readily standardized for each operator. Standardization of the area covered by the net allows density of collected nekton to be calculated. Little is known about the life cycle of one important estuarine dependent sport fish, tarpon (Megalops atlanticus), in southeastern Louisiana. This research details the presence of the major life stages of the species in Louisiana and suggests that it is capable of completing its life cycle in State waters. The presence of a spawning capable female and male tarpon is documented.

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Childs, Amber-Robyn. "Movement patterns of spotted grunter, Pomadasys commersonnii (Haemulidae), in a highly turbid South African estuary". Thesis, Rhodes University, 2006. http://hdl.handle.net/10962/d1005149.

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The principal objective of this thesis was to gain an understanding of the movement patterns of spotted grunter Pomadasys commersonnii, an estuarine-dependent fishery species, in the turbid, freshwater dominated Great Fish Estuary. Both manual and automated telemetry methods were used to monitor the movements of spotted grunter during two separate studies conducted in summer and spring 2003 and 2004. Acoustic transmitters were surgically implanted into twenty spotted grunter with lengths between 263 and 387 mm TL in the first study and twenty spotted grunter ranging between 362 and 698 mm TL in the second study. The specific objectives were to gain an understanding of (i) the time spent in the estuarine environment (ii) the space use and home range size, and (iii) the abiotic factors governing the movement patterns of spotted grunter in the estuary. The nursery function of estuarine environments was highlighted in this study as adolescent spotted grunter spent a significantly larger proportion of their time in the estuary than adult fish (p < 0.0001; R² = 0.62). The increased frequency of sea trips, with the onset of sexual maturity, provided testimony of the end of the estuarinedependent phase of their life-cycle. Although considered to be predominantly marine, the adult spotted grunter in the Great Fish Estuary utilised the estuary for considerable periods. Adults are thought to frequent estuaries to forage, seek shelter and to possibly rid themselves of parasites. During this study, the number of sea trips made by tagged fish ranged from 0 to 53, and the duration ranged from 6 hours to 28 days. The tidal phase and time of day had a significant effect (p < 0.05) on the sea trips undertaken by fish. Most tagged spotted grunter left the estuary during the night (84%) on the outgoing tide, and most returned in the evening (77%) during the incoming tide. Sea temperature (p < 0.0001; R² = 0.34), barometric pressure (p = 0.004; R² = 0.19) and wind (p = 0.01) had a significant effect on the number of spotted grunter recorded in the estuary. Spotted grunter were more prone to return to the estuary after high barometric pressure, when low sea temperatures (upwelling events) prevailed. There was a significant positive relationship between home range size and fish length (p = 0.004; R² = 0.20). Small spotted grunter (< 450 mm TL) appeared to be highly resident, with a small home range (mean size = 129 167 m²), that was generally confined to a single core area. Larger individuals (> 450 mm TL) occupied larger home ranges (mean size = 218 435 m²) with numerous core areas. The home ranges of small and large spotted grunter overlapped considerably yielding evidence of two high use areas, situated 1.2 km and 7 km from the mouth of the Great Fish Estuary. Tagged spotted grunter were located in a wide range of salinity, turbidity and temperature, but were found to avoid temperatures below 16 ºC. The daily change in environmental variables (salinity, temperature and turbidity) had a significant effect on the change in fish position in the estuary (p < 0.0001; R² = 0.38). The distribution of tagged spotted grunter, particularly the larger individuals, in the Great Fish Estuary was influenced by the tidal phase (p < 0.05); they moved upriver on the incoming tide and downriver on the outgoing tide. This study provides an understanding of the movement patterns of spotted grunter in the estuary and between the estuarine and marine environments. Consequently, it provides information that will assist in the design of a management plan to promote sustainability of this important fishery species. The techniques used and developed in this study also have direct application for further studies on other important estuarinedependent fishery species.

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Lukey, James Robert. "The ichthyofauna in a small temporarily open/closed Eastern Cape estuary, South Africa". Thesis, Rhodes University, 2006. http://hdl.handle.net/10962/d1005131.

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The ichthyofaunal community structure, population dynamics and movement patterns in the small temporarily open/closed (TOCE) Grant’s Valley estuary, situated along the Eastern Cape coastline, were investigated over the period May 2004 to April 2005. Community structure in the littoral zone was assessed, while growth of selected ichthyofaunal species was investigated using the MULTIFAN model. Population size was assessed using mark recapture models and movement within the estuary using the Hilborn (1990) model. Total ichthyofaunal densities and biomass within the littoral zone ranged between 0.31 to 21.45 fish m⁻² and 0.20 to 4.67 g wwt m⁻², with the highest values typically recorded during the summer. Results of the study indicated that the ichthyofaunal community structure within the estuary was closely linked to the mouth phase and the establishment of a link to the marine environment via overtopping events. In the absence of any link to the sea, the ichthyofaunal community was numerically dominated by estuarine resident species, mainly Gilchristella aestuaria and to a lesser extent, by the river goby, Glossogobius callidus which collectively comprised ca. 88% of all fish sampled. The establishment of the link to the marine environment contributed to an increased contribution of marine breeding species (e.g. Rhabdosargus holubi, Myxus capensis and Atherina breviceps) to the total ichthyofaunal abundances. In contrast, total ichthyofaunal biomass was almost always dominated by marine breeding species by virtue of their larger sizes. Results of hierarchical cluster analyses did not identify any spatial patterns in the ichthyofaunal community within the littoral zone. Results of MULTIFAN analysis indicated estuarine resident fish species bred over an extended period with peaks occurring in the summer months. Conversely, marine breeding fish were shown to recruit into the estuary following overtopping and breaching events. Results of the mark-recapture experiment indicated a population of ca. 12 000 (11 219 – 13 311) individuals greater than 50mm SL. Marine-breeding species (R. holubi, Monodactylus falciformis, and two mullet species) numerically dominated the ichthyofauna, possibly as a result of their effective use of overtopping events. The two mullet species, M. capensis and Liza richardsonii, and the Cape stumpnose, R. holubi moved extensively throughout the estuary, while the remaining species exhibited restricted movement patterns possibly due to the preference for refuge and foraging areas associated with reed beds. The observed movement patterns of individual fish species appeared to be associated with both foraging behaviour and habitat selection.

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NEVES, ROBERTA LYRIO SANTOS. "EVALUATION OF THE OIL CONTAMINATION OF THE ESTUARINE ENVIRONMENT OF THE GUANABARA BAY (RJ) BY THE FLUOROMETRIC DETERMINATION OF POLYCYCLIC AROMATIC HYDROCARBONS (PAHS) IN THE MUGIL LIZA FISH BILE". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2006. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=8681@1.

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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
Os Hidrocarbonetos Policíclicos Aromáticos (HPAs) são poluentes ubíquos na natureza sendo os derrames de óleo uma das principais fontes destes compostos para os ambientes aquáticos costeiros. Este trabalho avalia a possibilidade de uso dos metabólitos de HPAs na bílis do peixe Mugil liza (tainha) como biomarcadores no monitoramento ambiental de ecossistemas aquáticos. Para esta avaliação realizou-se um monitoramento sazonal na Baía de Guanabara, RJ, área cronicamente contaminada por óleo, e em Itaipu, Niterói, RJ, como área controle. Nos locais de coleta foram medidos parâmetros físico-químicos tais como, pH, oxigênio dissolvido, entre outros e selecionados os peixes variando entre 35 e 51 cm para maior homogeneidade das amostras. Em laboratório foram feitas medidas morfométricas dos indivíduos e retirado o seu líquido biliar. O método analítico foi otimizado e seus parâmetros de desempenho analítico foram determinados. As amostras de líquido biliar foram diluídas em etanol 48% (1:2000 v/v) e analisadas por fluorescência nos comprimentos de onda de excitação e emissão, respectivamente, 332 nm e 383 nm. A média das concentrações de HPAs totais na bílis dos peixes coletados na Baía de Guanabara foi significativamente diferente da área controle, Itaipu. Na Baía de Guanabara, valores de 7,0 ± 3,4 (n=19) e 10,4 ± 6,4 (n=12) mg de equivalentes (eqv.) de pireno L-1 foram obtidos, respectivamente, no inverno e no verão. Em Itaipu, a concentração de HPAs foi de 1,8 ± 0,7 (n=11) mg de eqv. de pireno L-1. Estes resultados indicam que o método é capaz de diferenciar áreas recentemente contaminadas por óleo de áreas não contaminadas, sendo o peixe Mugil liza um possível biomonitor para esta área. Este método analítico apresenta vantagens em relação a outros métodos, tais como tempo e custo de análise reduzidos, podendo ser usado em levantamento de dados preliminares nos programas de monitoramento ambiental.
Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in the environment. The main source of contamination is antropogenic, and oil spills are one of the main PAHs sources for the aquatic environment. This work evaluates the usage of PAH metabolites in fish bile (Mugil liza) as biomarkers in the aquatic environment. For this evaluation two distinct areas were monitores: Guanabara Bay, RJ, known for its chronic oil contamination, and Itaipu, Niterói, RJ, the control area. Physico-chemical measurements: pH, dissolved oxygen, conductivity and transparency were made in situ and fish varying from 35 to 50 cm were selected for sampling homogeneity and sexual maturity. In the laboratory, morphometric measures were taken and the fish bile was extracted. After optimizing the analytical method the samples were analysed by diluting each bile sample in ethanol 48% (1:2000 v/v) and fluorimetric measurements were made in excitation/emission wavelengths of 332 nm/383 nm. The mean total PAHs concentrations in the bile samples collected in the Guanabara Bay were significantly different from the control area, Itaipu. In the Guanabara Bay the means were 7,0 ± 3,4 (n=19) and 10,4 ± 6,4 (n=12) mg L-1 pyrene equivalents, in winter and summer, respectively. In Itaipu, the mean HPA concentration was 1,8 ± 0,7 (n=11) mg L-1 pyrene equivalents. These results indicate that this method can differentiate contaminated areas from non contaminated ones, making the fish Mugil liza one possible biomonitor in the Guanabara Bay, RJ. Additionally, this analytical method has advantages compared to other methods because it is less time consuming and is inexpensive and therefore could be used as a preliminary monitoring tool.

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Wasserman, Ryan. "The importance of estuarine head waters for fishes in selected Eastern Cape systems, with particular emphasis on the influence of freshwater inflow, migration barriers and non-native predators on the juvenile and small fish component". Thesis, Nelson Mandela Metropolitan University, 2010. http://hdl.handle.net/10948/1457.

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The utilisation of estuary headwater environments by young estuary- and marine-spawned fish species was investigated together with the effects of riverflow alteration, in-stream barrier effects and non-native ichthyofauna on the nursery function of these habitats. The distribution and abundance of young estuary- and marine-spawned fish were sampled using seine and fyke nets in the headwater environments of four permanently open Eastern Cape systems, namely the Great Fish, Kowie, Kariega and Sundays Estuaries. Within the suite of study systems, the first of two case studies focussed on barrier effects of in-stream structures on fish migration. This was undertaken in the Sundays River. In the second case study, predation and competition dynamics of the non-native piscivorous Micropterus salmoides on estuary-dependent fish was investigated in the estuary headwater regions of the Kowie River system. In all four estuaries, young estuary-spawned fish species dominated the ichthyofaunal community followed by marine-spawned species, despite varied freshwater inflow resulting in headwaters varying in salinity from fresh to hypersaline. Fish community structure however, differed largely between estuaries, with both freshwater abstraction and unnatural elevation of freshwater into estuaries, as a result of inter-basin transfers, affecting these communities. In-stream structures were found to effect upstream movement of fish in two ways, dependent on the type of barrier. Partial (size-dependent) and complete (species-dependent) restriction to upstream migration of fish by causeway-type instream structures were observed. Weir-type in-stream structures acted as a complete barrier to most species, regardless of fish size. Predation of estuary- and marine-spawned fish species by large sized M. salmoides was recorded, although these fish did not contribute significantly to their diet during this study. However, the main dietary components found in smaller sized M. salmoides stomachs overlap with those of juvenile estuary- and marinespawned fish species, suggesting feeding competition between the juveniles of indigenous and non-native fish species.

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Lechêne, Alain. "Trajectoire de restauration des marais intertidaux : réponse du necton à la dépoldérisation dans l’estuaire de la Gironde". Thesis, Bordeaux, 2017. http://www.theses.fr/2017BORD0883/document.

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Dégradés par plusieurs siècles d’endiguement et menacés par les effets du changement climatique, les marais intertidaux européens font aujourd’hui l’objet d’un nombre croissant de restaurations par rétablissement des marées sur d’anciennes zones endiguées, suivant une tendance générale appelée dépoldérisation. Cette thèse décrit la trajectoire de restauration des marais intertidaux à partir des communautés de necton (i.e., poissons et crustacés décapodes), sur la base de deux sites dépoldérisés accidentellement dans l’estuaire de la Gironde : le marais de Mortagne et l’île Nouvelle. L’évolution du necton dans les marais dépoldérisés est caractérisée à travers une approche synchronique à l’échelle de la mosaïque des habitats estuariens. La composition du necton dans les marais dépoldérisés est en grande partie similaire à celles des milieux intertidaux naturels et se différencie nette-ment des marais endigués, où les espèces exotiques d’eau douce prospèrent. Les marais restaurés apparaissent particulièrement attractifs pour le mulet porc, Liza ramada. La distribution des traits fonctionnels au sein des communautés de poissons révèle un changement de structure fonctionnelle au cours de la dépoldérisation, le temps de restauration étant inféré à partir d’un gradient de naturalité des habitats estuariens. En particulier, la spécialisation, la dispersion et la richesse fonctionnelle augmentent au cours de la restauration. Concernant l’évolution des règles d’assemblage, aucune tendance claire ne se dégage : les patrons diffèrent selon les traits fonctionnels.La dynamique temporelle de la composition des communautés de necton dans l’un des sites dépoldérisés montre une succession de trois phases au cours des quatre années suivant la restauration. Un changement plus abrupt concernant l’abondance de certaines espèces et la structure fonctionnelle des communautés est identifié au milieude la seconde phase, moins de deux ans après la dépoldérisation. La cinétique de transformation des communautés est probablement ralentie par le drainage incomplet du site dans les premiers temps de la dépoldérisation. Les résultats de cette thèse permettent de mieux comprendre la trajectoire de restauration des marais intertidaux, sans intervention humaine, tout en soulignant les atouts et les limites de certains modèles théoriques utilisés en écologie de la restauration
European intertidal marshes have greatly declined during the past centuries because of land claim andhave recently been threatened by the effects of climate change. In recent years, an increasing number of tidal resto-ration projects have been implemented, following a global trend termed de-embankment. This thesis describes therestoration trajectory of tidally restored marshes from the response of nekton (i.e., fish and decapod crustaceans)based on two storm-breached study sites in the Gironde estuary : the Mortagne marsh and the Nouvelle island.Nekton assemblage composition of tidally restored marshes was described through a whole-estuary approach en-compassing natural, restored and dyked habitats. Nekton assemblages of tidally restored marshes showed highcompositional similarity with natural intertidal habitats and greatly departed from dyked marshes. Dyked marsheswere characterized by high occurrence of freshwater exotic taxa. Tidally restored marshes seemed particularly at-tractive for the thin-lipped grey mullet, Liza ramada. The functional traits’ distribution within fish communities revealeda change in functional structure in the course of restoration using the naturalness state of habitats as a proxy forrestoration time. Most notably, functional specialization, dispersion and richness increased with restoration time.No clear pattern of change was observed in community assembly over time ; trends chiefly varied with respect totraits. Temporal trends in one of the restored sites revealed three phases in the first four years of tide restoration.The abundance of several species and the community functional structure changed more steeply in the midst ofthe second phase, less than two years following tide restoration. Community turnover was probably delayed dueto incomplete drainage of the site in the early stages of restoration. The results of this thesis lead to a better un-derstanding of the restoration trajectory of tidal marshes without human intervention and highlight the strengths andweaknesses of some theoretical models used in restoration ecology

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Pinto, Samara Macedo. "Mudan?as a longo prazo na comunidade de peixes de uma ba?a tropical do sudeste do Brasil (1987-2013): perda gradativa da biodiversidade da zona interna para zona externa". Universidade Federal Rural do Rio de Janeiro, 2015. https://tede.ufrrj.br/jspui/handle/jspui/1754.

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Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES
Fish communities in developing countries have, in many cases, showed a decrease in the species richness and abundance over time as a result of anthropogenic impacts. We analyzed fish communities of three zones (inner, middle and outer) of the Sepetiba Bay (Southeastern Brazil) using identical sampling methods (bottom trawl) during four different time periods: 1987?1988; 1993?1995; 1998?2001 and 2012?2013. A total of 33,140 fish representing 127 species in 88 genera and 41 families were recorded. Our results revealed highly significant and consistent differences in the fish community structure among the bay zones, and a decreased in the fish richness and abundance over the time period. Changes in fish richness and abundance were related mostly to a sharp decrease that occurred in the inner bay zone, the most impacted bay area, and, to a lesser extent, in the middle zone between the two first (1987?1988 and 1993?1995) and the two latter time periods (1998?2001 and 2012?2013), whereas the outer zone remained comparatively stable over time. Spatial changes in the fish community structure among the bay zones were related to differences in salinity, transparency and depth with this latter variable, together with other factors, acting as a buffer for stabalizing community changes; however, these environmental variables explained little of the variation in the temporal changes. The most important changes over time in abundant species were the numerical decreases of the Ariid Cathorops spixii, the serranid Diplectrum radiale and sciaenid Cynoscion leiarchus, and increases of the sciaenid Micropogonias furnieri and the marine catfish Genidens genidens, with this latter species restricted to the inner and middle zones. This study adds long-term information on gradual fish community changes along spatial gradients of environmental and anthropogenic influences in embayment systems. It is perhaps timely to link conservation and management planning with historical information to protect fish biodiversity in tropical developing countries
As comunidades de peixes em pa?ses em desenvolvimento, em muitos casos, mostram uma diminui??o na riqueza e abund?ncia das esp?cies ao longo do tempo como resultado das evid?ncias dos impactos antropog?nicos. N?s analisamos as comunidades de peixes ao longo de tr?s zonas (interna, central e externa) da Ba?a de Sepetiba (Sudeste do Brasil), utilizando m?todos id?nticos de amostragem (bottom trawl) de peixes durante quatro per?odos temporais diferentes: 1987?1988; 1993?1995; 1998?2001 e 2012?2013. Registrou-se um total de 33.140 peixes representando 127 esp?cies em 88 g?neros e 41 fam?lias. Nossos resultados revelaram diferen?as altamente significativas e consistentes na estrutura da comunidade de peixes entre as zonas da ba?a e uma diminui??o na riqueza de esp?cies e abund?ncia ao longo do per?odo de estudo. As mudan?as na riqueza de esp?cies e abund?ncia foram relacionadas, principalmente, ? uma forte queda que ocorreu na zona interna da ba?a, ?rea esta mais afetada e, em menor medida, na zona central entre os dois primeiros (1987?1988 e 1993?1995) e os ?ltimos dois per?odos temporais (1998?2001 e 2012?2013), enquanto a zona exterior permaneceu relativamente est?vel ao longo do tempo. Mudan?as espaciais na estrutura da comunidade de peixes entre as zonas da ba?a foram relacionadas ?s diferen?as de salinidade, transpar?ncia e profundidade com este ?ltima vari?vel, em conjunto com outros fatores, atuando como um ?buffer? estabilizando mudan?as na comunidade; no entanto, essas vari?veis ambientais explicaram pouco a varia??o nas mudan?as temporais. As mudan?as mais importantes ao longo do tempo em esp?cies abundantes foi a diminui??o num?rica do Ariideo Cathorops spixii, do Serran?deo Diplectrum radiale e do Sciaen?deo Cynoscion leiarchus, e o aumento do Sciaen?deo Micropogonias furnieri e o bagre marinho Genidens genidens, com esta ?ltima esp?cie restrita ?s zonas interna e central. Este estudo acrescenta informa??o de longo prazo sobre mudan?as graduais nas comunidades de peixes ao longo de gradientes espaciais com influ?ncias ambientais e antr?picas no sistema de ba?a. Talvez seja oportuno vincular conserva??o e planejamento de gest?o com informa??es hist?ricas para proteger a biodiversidade de peixes em pa?ses tropicais em desenvolvimento.

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Blake, Justin David. "The ichthyofauna and piscivorous avifauna in a small temporarily open/closed Eastern Cape estuary, South Africa". Thesis, Rhodes University, 2010. http://hdl.handle.net/10962/d1005395.

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The spatial and temporal patterns in selected components of the ichthyofauna and piscivorous avifauna in the small temporarily open/closed Riet River Estuary located on the eastern seaboard of southern Africa was investigated monthly over the period August 2005 to July 2006. The ichthyofauna within the littoral zone of the estuary was sampled using a 5 m seine net (8 stations) while a 30 m seine net (4 stations) was employed to sample the fish in the channel. Bird counts were made along repeat transects along the length of the estuary. Total ichthyofaunal abundances and biomass ranged between 1.60 and 8.67 individuals m⁻² and 0.45 to 21.76 g wwt m⁻² within the littoral zone, and between 0.08 and 0.44 individuals m⁻² and 0.58 and 36.52 g wwt m⁻² in the channel of the estuary. The highest values were generally recorded during the summer months. Results of the numerical analysis indicated that the breaching events recorded over the study period did not lead to a common trend in the ichthyofaunal community. In the absence of a link to the marine environment, the ichthyofaunal community in the littoral zone was numerically dominated by the estuarine resident species, Gilchristella aestuaria and to a lesser extent by Glossogobius callidus, which collectively accounted for ca. 54% of the total ichthyofauna sampled. The establishment of a link to the marine environment coincided with increased numbers of marine breeding species including Atherina breviceps and Rhabdosargus holubi to total fish counts within the estuary. Hierarchical cluster analysis did not identify any spatial patterns in the community structure of the ichthyofauna in the littoral zone or channel zone of the estuary, which could likely be linked to the absence of any distinct horizontal patterns in salinity and temperature within the system. A total of thirteen piscivorous bird species was recorded over the study period. Of the recorded species, six species were wading piscivores, four species were aerial divers and the remaining three species were pursuit swimmers. There were no significant correlations between the estimates of the ichthyofaunal abundance and biomass and bird numbers evident during the study (P> 0.05 in both cases). The Reed Cormorant (Phalacrocorax africanus) was the dominant species throughout the study, with a mean of 8.25 (SD ± 7.90) individuals per count. Mean values of the Pied Kingfisher (Ceryle rudis) and Giant Kingfisher (Megaceryle maximus) were 3.42 (SD ± 1.20) and 1.17 (SD ± 0.60) individuals per count, respectively. The remaining species revealed mean values < 0.5 individuals per count. The highest bird numbers were recorded in winter reflecting the migration of large numbers of the Reed Cormorant into the system. Breaching events were associated with a decrease in total bird numbers, which was most likely due to loss of potential foraging habitat (littoral zone) for waders resulting from reduced water levels. Monthly food consumption by all piscivorous birds revealed large temporal variability, ranging from 26.35 to 140.58 kg per month. The observed variability could be linked to mouth phase and bird numbers.

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Rozprawy doktorskie na temat „Estuarine fish”

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