Journal articles on the topic 'Estuarine fish'
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1
Gillanders, Bronwyn M., Travis S. Elsdon, Ian A. Halliday, Gregory P. Jenkins, Julie B. Robins, and Fiona J. Valesini. "Potential effects of climate change on Australian estuaries and fish utilising estuaries: a review." Marine and Freshwater Research 62, no. 9 (2011): 1115. http://dx.doi.org/10.1071/mf11047.
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Estuaries are especially vulnerable to the impacts of climate change because changes in climatic and hydrologic variables that influence freshwater and marine systems will also affect estuaries. We review potential impacts of climate change on Australian estuaries and their fish. Geographic differences are likely because southern Australian climates are predicted to become warmer and drier, whereas northern regions may see increased precipitation. Environmental factors, including salinity gradients, suspended sediment, dissolved oxygen and nutrient concentrations, will be influenced by changing freshwater input and other climate variables. Potential impacts will vary depending on the geomorphology of the estuary and the level of build-up of sand bars across estuarine entrances. Changes to estuarine fish assemblages will depend on associated changes to salinity and estuarine-mouth morphology. Marine migrants may be severely affected by closure of estuarine mouths, depending on whether species ‘must’ use estuarine habitat and the level of migratory v. resident individuals. Depending on how fish in coastal waters locate estuaries, there may be reduced cues associated with estuarine mouths, particularly in southern Australia, potentially influencing abundance. In summary, climate change is expected to have major consequences for Australian estuaries and associated fish, although the nature of impacts will show significant regional variation.
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O'Mara, K., A. Miskiewicz, and M. Y. L. Wong. "Estuarine characteristics, water quality and heavy metal contamination as determinants of fish species composition in intermittently open estuaries." Marine and Freshwater Research 68, no. 5 (2017): 941. http://dx.doi.org/10.1071/mf15409.
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Estuaries are critical aquatic environments that are used by many fish during their life cycle. However, estuaries often suffer from poor water quality as a result of anthropogenic activities. Fish diversity studies in estuaries are common, although few have examined whether correlations exist between water quality, metal contamination and fish assemblages. In the present study we investigated the effect of abiotic conditions, heavy metals and estuary characteristics on the abundance, diversity and composition of fish in four intermittently open estuaries along the Illawarra coast of south-eastern Australia. The heterogeneity of environmental conditions was reflected in the fish assemblages in each estuary. Environmental variables predicted fish species composition, and estuaries in particularly poor condition contained few species (estuarine residents) in high abundance, indicating their ability to acclimatise and survive in conditions that are hostile to other species. Overall, these findings demonstrate that estuarine fish assemblages may be useful indicators of estuary condition and reveal the importance of managing anthropogenic activities in the surrounding catchment to improve water quality so that biodiversity of fish can be restored in these estuarine environments.
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Taddese, Fasil, Marc Schallenberg, Pavel Mikheev, Matt G. Jarvis, and Gerard P. Closs. "Ichthyofaunal assemblages in shallow littoral habitats of permanently open estuaries and intermittently closed and open lakes or lagoons in Otago, New Zealand." Marine and Freshwater Research 69, no. 8 (2018): 1222. http://dx.doi.org/10.1071/mf17334.
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Fish assemblages of New Zealand estuaries are poorly studied, and knowledge of the effects of estuary–ocean connections on the ichthyofaunal composition of estuaries remains limited. Understanding the status of fish composition of estuaries is crucial for planning for sustainable management of aquatic ecosystems. In the present study we sampled fish using a seine net from lower reaches of six permanently open estuaries and six intermittently closed and open lakes or lagoons (ICOLLs) along the Otago coastline during winter 2016 and summer 2017. Marked differences in ichthyofaunal composition were observed in the shallow littoral habitats of permanently open estuaries and ICOLLs. Fish assemblages reflected estuary–ocean connection status of estuaries during both seasons. ICOLLs showed greater fish abundance than permanently open systems. Fish abundance was higher in summer than in winter in both estuary types. Fish species with marine–estuarine opportunist and estuarine–migrant life histories dominated permanently open estuaries. Conversely, species with a diadromous life history but known to form landlocked populations were abundant in ICOLLs. Salinity and temperature were correlated with fish abundance in both estuary types.
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Silva Junior, Milton Goncalves, Antonio Carlos Leal Castro, and Ulrich Saint-Paul. "Comparative Analysis of Distribution of Intertidal Fish Assemblages in Different Estuarine Systems on Northern Coast of Brazil." Journal of Sustainable Development 10, no. 2 (March 30, 2017): 26. http://dx.doi.org/10.5539/jsd.v10n2p26.
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The northern coast of Brazil has more than 30 estuaries distributed along 650 km of coastline. These conditions favor the presence of relatively large fish communities in estuarine environments, but published information on the fish fauna in tidal creeks in northern Brazil is only available for some mangrove systems, and comparative studies between fish estuarine communities in different tidal creeks are less common. The choice of the study area was based on the fact that it has been poorly investigated with regard to estuarine fish fauna in comparison in mangrove tidal creeks using the same fishing gear. The objective of the present study was to compare the composition of the relative biomass of taxonomic, functional and ecological guilds of fish assemblages occurring in estuarine systems along the northern coast of Brazil. The study area of the present comparative analysis extended from the southeastern edge of the Marajoara Gulf to the western edge of the Maranhense Gulf. A comparative analysis among different estuarine systems was performed using data from other studies. The abundance of juveniles was greater in the Caeté, Curuçá and Cururuca estuaries than other estuaries. Cluster analysis separated the estuaries into two distinct groups and significant differences between these groups only exist in relation to geographical proximity. The present investigation indicates that the coastal region between the states of Pará and Maranhão is characterized by high dynamics and environmental heterogeneity, particularly with regard to changes in river discharge and tidal fluctuations. The present results underscore the importance of ecological information on ichthyofauna in tropical estuaries in order to include appropriate descriptors in conservation or restoration processes of marine communities and habitats.
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Whitfield, AK. "Littoral habitats as major nursery areas for fish species in estuaries: a reinforcement of the reduced predation paradigm." Marine Ecology Progress Series 649 (September 10, 2020): 219–34. http://dx.doi.org/10.3354/meps13459.
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For many decades, the role of estuaries as important nursery areas for fishes was accepted as fact by scientists and environmental managers. At the turn of the 21st century, a question mark was raised in relation to the reduced predation component of the nursery function, with some scientists contending that both large and small piscivorous fish species had access to the estuarine habitats that juvenile fishes in estuaries occupied. If true on a global scale, the nursery designation for these habitats would be compromised and the long-held paradigm that estuaries are important nursery areas for fishes would need to be revised. In this review, I examine the nature of fish nursery areas in estuarine littoral habitats from a mainly predation perspective and, based on a variety of ichthyofaunal and avifaunal studies, come to the conclusion that apart from a few selected estuarine systems, there is limited predation on juvenile fishes in these particular areas. This, coupled with the abundant suitable food resources for juvenile fish from different trophic categories, shelter from high-energy marine wave action and biological connectivity between a variety of submerged and emergent macrophyte communities, renders shallow estuarine littoral areas ideal nursery areas for the juveniles of mostly euryhaline marine fish species, the dominant component of estuarine ichthyofaunas globally. In addition, there are strong indications from the fossil record that these littoral estuarine nursery areas have been functioning since the Devonian, more than 350 million years ago.
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Henderson, Christopher J., Ben L. Gilby, Edward Stone, Hayden P. Borland, and Andrew D. Olds. "Seascape heterogeneity modifies estuarine fish assemblages in mangrove forests." ICES Journal of Marine Science 78, no. 3 (February 12, 2021): 1108–16. http://dx.doi.org/10.1093/icesjms/fsab022.
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Abstract Mangroves are a dominant structural habitat within tropical and subtropical estuaries that provide a number of ecosystem services, including habitat for a range of crustaceans and fish. However, mangroves are one of the most threatened estuarine habitats globally, having been severely reduced in extent, and replaced by urban structures. Here, we test for the effects of both natural (e.g. seagrass, rock and mangroves habitat extent, and connectivity) and human (e.g. extent of urban area) landscape variables on the number and type of fish inhabiting mangroves forests. We used remote underwater video stations to quantify fish assemblages within mangroves at 150 sites in 30 estuaries across Queensland, Australia. Fish community structure was best explained by the extent of mangroves and seagrasses within an estuary, the distance to the estuary mouth, and the size of the estuary and catchment. Moderate catchment size and proximity to the estuary mouth increased species richness and abundance of harvestable fish at individual mangrove sites. In order to maintain mangrove fish assemblages and the functions they provide, management initiatives should focus on maintaining natural estuarine seascapes that are located closer to the mouth of estuaries, in particular, focusing on estuaries that have lower levels of catchment urbanization.
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Ramos, S., C. B. Paris, and M. M. Angélico. "Larval fish dispersal along an estuarine–ocean gradient." Canadian Journal of Fisheries and Aquatic Sciences 74, no. 9 (September 2017): 1462–73. http://dx.doi.org/10.1139/cjfas-2016-0325.
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The present study investigated the larval fish dispersal along an estuarine–ocean gradient to explore connectivity between ocean and estuaries. During spring 2009, a combined ocean–estuarine survey was conducted along the Lima estuarine salinity gradient and in two transects off the adjacent coast (northwestern Iberian Peninsula), until the 100 m isobaths. Salinity, total particulate matter, particulate organic matter, total dissolved carbon, and dissolved organic carbon reached higher values at the ocean, and chlorophyll a and nutrients increased at the estuary. From the total 56 taxa identified, 14 were present along the gradient, including estuarine species (ES), marine stragglers (MS), and migrants (MM). Canonical correspondence analysis showed that species were separated along the gradient according to their ecological functional classification. MM associated with high salinity were separated from ES correlated with lower salinities and high chlorophyll a concentrations of inner estuary. Flounder (Platichthys flesus) showed a typical spatial gradient of MM, with abundance increasing from the ocean towards inner estuary. The dispersal of larvae along the Lima estuarine–ocean gradient was indicative of connectivity between habitats, emphasizing the need to consider this feature in management plans, mainly for species exploited by commercial fisheries.
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Zampatti, Brenton P., Christopher M. Bice, and Paul R. Jennings. "Temporal variability in fish assemblage structure and recruitment in a freshwater-deprived estuary: The Coorong, Australia." Marine and Freshwater Research 61, no. 11 (2010): 1298. http://dx.doi.org/10.1071/mf10024.
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River regulation can diminish freshwater flows to estuaries and compromise estuarine functionality. Understanding biotic responses to altered flow regimes is imperative to effectively manage aquatic ecosystems. The present study investigated temporal variation in fish assemblage structure and the recruitment of catadromous fish in the Coorong estuary at the terminus of the Murray River, in south-eastern Australia. Over the three-year study period, freshwater inflows to the estuary diminished and ultimately ceased, disconnecting freshwater and estuarine environments. It was hypothesised that these conditions would lead to (1) increases in estuarine salinities and concomitant changes in fish assemblage structure and abundance, and (2) decreased recruitment of catadromous fish. As freshwater inflow decreased, salinities immediately downstream of a series of tidal barrages increased from brackish to marine–hypersaline, species richness and diversity decreased, freshwater and diadromous species became less abundant and assemblages were increasingly characterised by marine species. Furthermore, the abundance of young-of-year catadromous fish decreased dramatically. Excessive regulation of freshwater inflows is resulting in the Coorong estuary resembling a marine embayment, leading to a loss in species diversity. We suggest, however, that even small volumes of freshwater may promote diversity in estuarine fish assemblages and some recruitment of catadromous species.
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Henderson, Christopher J., Ben L. Gilby, Thomas A. Schlacher, Rod M. Connolly, Marcus Sheaves, Nicole Flint, Hayden P. Borland, and Andrew D. Olds. "Contrasting effects of mangroves and armoured shorelines on fish assemblages in tropical estuarine seascapes." ICES Journal of Marine Science 76, no. 4 (February 4, 2019): 1052–61. http://dx.doi.org/10.1093/icesjms/fsz007.
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Abstract Coastal seascapes are composed of a diversity of habitats that are linked in space and time by the movement of organisms. The context and configuration of coastal ecosystems shapes many important properties of animal assemblages, but potential seascape effects of natural and artificial habitats on nearby habitats are typically considered in isolation. We test whether, and how, the seascape context of natural and urban habitats modified fish assemblages across estuaries. Fish were sampled with underwater videos in five habitat types (mangroves, rock bars, log snags, unvegetated sediments, armoured shorelines) in 17 estuaries in eastern Australia. Different habitats supported distinct fish assemblages, but the spatial context of mangroves and armoured shorelines had pervasive ecological effects that extended across entire estuaries. In most estuarine habitats, fish diversity and abundance was greatest when they were in close proximity of mangroves, and decreased due to the proximity of armoured shorelines. Many cities are centred on estuaries, and urban expansion is often associated with the fragmentation of mangrove forests. Our findings emphasize that these transformations of urban estuarine landscapes are likely to propagate to broader ecological impacts detectable in multiple habitats beyond mangrove forests.
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Ashford, J. R., C. M. Jones, E. Hofmann, I. Everson, C. Moreno, G. Duhamel, and R. Williams. "Can otolith elemental signatures record the capture site of Patagonian toothfish (Dissostichus eleginoides), a fully marine fish in the Southern Ocean?" Canadian Journal of Fisheries and Aquatic Sciences 62, no. 12 (December 1, 2005): 2832–40. http://dx.doi.org/10.1139/f05-191.
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Otolith chemistry has been successfully used to reconstruct the environmental history experienced by estuarine-dependent teleost fish, including movement between estuaries and coastal areas. However, application has been more limited in species exposed exclusively to oceanic waters, where gradients in physical and chemical properties are less extreme. To test whether otolith elemental signatures record spatial information in an oceanic species, we sampled otoliths from Patagonian toothfish (Dissostichus eleginoides) and used an inductively coupled plasma mass spectrometer (ICP-MS) coupled to a laser ablation system to target the outer otolith edges corresponding to the period immediately before capture. Using multivariate analysis of variance and multivariate discriminant analysis, we found that edge signatures discriminated toothfish by geographic region with near complete success: only 5% of fish caught off South America and in the Antarctic were misclassified to sampling areas in the other region. Moreover, edge signatures showed strong differences between sampling areas within each region: fish captured off South America classified to sampling areas therein with 79%84% success, and Antarctic fish classified to sampling areas therein with 50%67% success. These results compare favourably with rates of classification for estuarine-dependent fish, demonstrating that otolith elemental signatures can discriminate the geographic provenance of oceanic and estuarine-dependent fish.
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Seriani, Robson, Lucas Buruaem Moreira, Denis Moledo de Souza Abessa, Laís D. Abujamara, Natashy S. B. de Carvalho, Luciane Alves Maranho, Aline A. Kirschbaum, and Maria José T. Ranzani-Paiva. "Hematological analysis of Micropogonias Furnieri, Desmarest, 1823, Scianidae, from two estuaries of Baixada Santista, São paulo Brazil." Brazilian Journal of Oceanography 58, spe3 (June 2010): 87–92. http://dx.doi.org/10.1590/s1679-87592010000700011.
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Hematological alterations in fish are considered a useful tool to evaluate pathological processes resulting from the exposure to environmental pollutants. The whitemouth croaker Micropogonias furnieri is a common species in estuarine areas and potentially exposed to many contaminants. In the present study, the hematological characteristics of fish collected at two sites in Baixada Santista (Santos Estuarine System - SES, a polluted site; and the Estuary of Itanhaém River - EIR, unpolluted site) del was analysed. The following blood descriptors were analyzed: number of Erythrocytes (Er), Hematocrit (Ht), Hemoglobin (Hb), Mean Corpuscular Volume (MCV) and Mean Corpuscular Hemoglobin concentration (MCHC). Fish from SES exhibited significant lower levels of Ht and increase on MCHC and Hb. Such differences are likely related to the different contamination levels found in these estuaries.
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Whitfield, A. "Predation on small juvenile fishes in shallow estuarine nursery areas: Reply to Baker & Sheaves (2021)." Marine Ecology Progress Series 662 (March 18, 2021): 209–14. http://dx.doi.org/10.3354/meps13678.
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The key criticism by Baker & Sheaves (2021; Mar Ecol Prog Ser 662:205-208) of the Whitfield (2020; Mar Ecol Prog Ser 649:219-234) estuarine littoral predation paradigm review is that shallow water fish nursery habitats contain abundant predator assemblages which may create high predation pressure on the juvenile fish cohorts that occupy these areas. The primary arguments supporting Baker & Sheaves’ criticism arise from a series of papers published by them on piscivorous fish predation in certain tropical Australian estuaries. The counter-argument that shallow littoral areas in estuaries do indeed provide small juvenile fishes with refuge from small and large piscivorous fishes is provided by published papers from 4 different estuary types in South Africa, covering both subtropical and warm-temperate systems. Based on the overall published information, the argument for shallow (<1 m depth) estuarine waters providing major protection for newly settled juveniles appears to be weak in northern Australia but strong in South Africa. The global situation, as outlined in this response, is more supportive of low piscivorous predation in shallow nursery habitats, but further targeted research is needed before we can confirm that littoral estuarine waters are indeed a universal keystone attribute in this regard.
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Martinho, Filipe, Henrique N. Cabral, Ulisses M. Azeiteiro, and Miguel A. Pardal. "Estuarine nurseries for marine fish." Management of Environmental Quality: An International Journal 23, no. 4 (June 8, 2012): 414–33. http://dx.doi.org/10.1108/14777831211232236.
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Passos, Ana Carolina dos, Riguel Feltrin Contente, Felippe Veneziani Abbatepaulo, Henry Louis Spach, Ciro Colodetti Vilar, Jean Christophe Joyeux, Beatriz Fernanda Chinhilla Cartagena, and Luis Fernando Fávaro. "Analysis of fish assemblages in sectors along a salinity gradient based on species, families and functional groups." Brazilian Journal of Oceanography 61, no. 4 (December 2013): 251–64. http://dx.doi.org/10.1590/s1679-87592013000400006.
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Here we test the effects of the east-west salinity gradient in the subtropical Paranaguá Bay Estuarine Complex (PEC) on the structure of shallow water fish fauna, determined according to taxonomic (families and species) and functional composition metrics. A total of 152 species were observed. The families with the largest number of species were the Sciaenidae, Carangidae, Haemulidae and Gobiidae. The most abundant species were Atherinella brasiliensis, Harengula clupeola, Anchoa januaria and Anchoa tricolor. Marine stragglers dominated in number of species, followed by marine migrants and estuarine species. Most species were zoobenthivores, followed by piscivores and zooplanktivores. Families and species more frequently associated with estuarine conditions dominated in the mesohaline sector, and those more frequently associated with marine conditions dominated in the euhaline sector. The fish assemblages along the estuarine salinity gradient were found to be better characterized by taxonomic metrics than by functional ones. This is most likely because individuals of all functional groups inhabit all salinity sectors, and thus these metrics are not useful for differentiating assemblages along salinity gradients. Our results differ from those of other studies in tropical and subtropical estuaries, which have emphasized the importance of functional groups in determining fish assemblages along salinity gradients.
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Nodo, P., N. C. James, A. R. Childs, and M. D. V. Nakin. "Response of demersal fish assemblages to an extreme flood event in a freshwater-deprived estuary in South Africa." Marine and Freshwater Research 69, no. 2 (2018): 253. http://dx.doi.org/10.1071/mf17096.
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The Kariega Estuary in South Africa, is an example of a freshwater-deprived estuary. Large-scale water abstraction and droughts have resulted in this estuary either being uniformly marine or hypersaline. A major episodic flood event in October 2012, the largest ever recorded in this system, provided us with an opportunity to investigate the prolonged effect of an episodic flood on the demersal fish assemblage of a freshwater-deprived estuary. A beam trawl net was used for sampling the fish assemblages from December 2013 to November 2014. The flood event before the sampling period ‘reset’ the system, such that there was a longitudinal salinity gradient from the head to the mouth, which resulted in ‘normal’ estuarine conditions, typical of most estuaries. There was an increase in the abundance of benthopelagic marine migrant species, particularly early juveniles of important fishery species, in the middle and upper reaches during the present study relative to previous studies conducted in this freshwater-deprived system. This suggests increased recruitment of these species into their estuarine nursery habitat. The present study highlights the importance of understanding the effect of freshwater inflow on the demersal estuarine fish assemblage and the nursery role of this and other estuarine systems and their management.
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Lonthair, Joshua, Rasmus Ern, and Andrew J. Esbaugh. "The early life stages of an estuarine fish, the red drum (Sciaenops ocellatus), are tolerant to high pCO2." ICES Journal of Marine Science 74, no. 4 (January 8, 2017): 1042–50. http://dx.doi.org/10.1093/icesjms/fsw225.
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Ocean acidification (OA) and other climate change induced environmental alterations are resulting in unprecedented rates of environmental deterioration. This environmental change is generally thought to be too fast for adaptation using typical evolutionary processes, and thus sensitivity may be dependent on the presence of existing tolerant genotypes and species. Estuaries undergo natural pCO2 fluctuations over a variety of time scales, and levels regularly exceed the predicted end of the century values. Interestingly, estuarine fish species have been overlooked in reference to the impacts of OA. Here, we use the estuarine red drum (Sciaenops ocellatus) as a model to explore the hypothesis that early life stages of estuarine species have intrinsic tolerance to elevated pCO2. Our sensitivity endpoints included: survival, growth, yolk consumption, heart rate, and scototaxis. Survival was significantly decreased when exposed to 1300 μatm and 3000 μatm, and coincided with a significant increase in heart rate at the 3000 μatm exposure. However, these effects were less pronounced than the findings of previous studies on other marine fish species. Yolk depletion rate and standard length were not significantly affected by pCO2. Scototaxis behaviour was also not significantly affected by exposure to elevated levels of pCO2 under both acute and acclimated exposure scenarios. Overall, these results support the hypothesis that estuarine life history and habitat usage may play a critical role in determining sensitivity of fish species to OA. Furthermore, estuarine species may provide present-day insight into the physiological and ecological foundation of OA tolerance.
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Murray, Taryn S., Paul D. Cowley, Rhett H. Bennett, and Amber-Robyn Childs. "Fish on the move: connectivity of an estuary-dependent fishery species evaluated using a large-scale acoustic telemetry array." Canadian Journal of Fisheries and Aquatic Sciences 75, no. 11 (November 2018): 2038–52. http://dx.doi.org/10.1139/cjfas-2017-0361.
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Connectivity — movements of animals between and among numerous habitats — and the factors (rhythmic cycles and environmental variables) influencing connectivity of juvenile Lichia amia (Teleostei: Carangidae) were assessed in complementary acoustic telemetry studies in two geographically separated estuaries (620 km apart) in South Africa. The studies were conducted within a nationwide array of acoustic receivers moored in estuaries and coastal waters. Tagged fish in both the Kowie (n = 21) and Goukou (n = 17) estuaries displayed high levels of multiple habitat connectivity, with 81% and 76% visiting nearby marine and estuarine environments, respectively. The presence of tagged L. amia within the tagging estuaries was significantly influenced by river and sea temperature (Kowie) and river inflow and moon phase (Goukou). Tidal phase, time of day, and season were found to significantly influence marine excursions undertaken by Kowie- and Goukou-tagged fish. Our study provides an assessment of connectivity among multiple estuarine, port, and marine habitats, relating those movements to rhythmic cycles and environmental variables, and highlights the benefits of tracking animals using an extensive acoustic receiver array that spans multiple habitats.
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Hutton, Sara J., Scott J. St. Romain, Emily I. Pedersen, Samreen Siddiqui, Patrick E. Chappell, J. Wilson White, Kevin L. Armbrust, and Susanne M. Brander. "Salinity Alters Toxicity of Commonly Used Pesticides in a Model Euryhaline Fish Species (Menidia beryllina)." Toxics 9, no. 5 (May 20, 2021): 114. http://dx.doi.org/10.3390/toxics9050114.
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Changing salinity in estuaries due to sea level rise and altered rainfall patterns, as a result of climate change, has the potential to influence the interactions of aquatic pollutants as well as to alter their toxicity. From a chemical property point of view, ionic concentration can increase the octanol–water partition coefficient and thus decrease the water solubility of a compound. Biologically, organism physiology and enzyme metabolism are also altered at different salinities with implications for drug metabolism and toxic effects. This highlights the need to understand the influence of salinity on pesticide toxicity when assessing risk to estuarine and marine fishes, particularly considering that climate change is predicted to alter salinity regimes globally and many risk assessments and regulatory decisions are made using freshwater studies. Therefore, we exposed the Inland Silverside (Menidia beryllina) at an early life stage to seven commonly used pesticides at two salinities relevant to estuarine waters (5 PSU and 15 PSU). Triadimefon was the only compound to show a statistically significant increase in toxicity at the 15 PSU LC50. However, all compounds showed a decrease in LC50 values at the higher salinity, and all but one showed a decrease in the LC10 value. Many organisms rely on estuaries as nurseries and increased toxicity at higher salinities may mean that organisms in critical life stages of development are at risk of experiencing adverse, toxic effects. The differences in toxicity demonstrated here have important implications for organisms living within estuarine and marine ecosystems in the Anthropocene as climate change alters estuarine salinity regimes globally.
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Bradbury, I. R., S. E. Campana, and P. Bentzen. "Low genetic connectivity in an estuarine fish with pelagic larvae." Canadian Journal of Fisheries and Aquatic Sciences 65, no. 2 (February 1, 2008): 147–58. http://dx.doi.org/10.1139/f07-154.
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We evaluated the spatial scale of metapopulation structure and genetic connectivity in rainbow smelt, Osmerus mordax, using eight microsatellite loci at 22 spawning locations throughout Newfoundland and Labrador. Consistent with low gene flow and limited dispersal, significant genetic structuring (FST ≈ 0.11) was present at small spatial scales (<200 km). Moreover, strong isolation by distance (IBD, P < 0.001, r2 = 0.47) was observed, which was linear at small scales and nonlinear at large distances (>200 km). We hypothesized that despite high dispersal potential associated with a pelagic larval stage, behaviours restricting gene flow may result in structuring at the estuary scale. Multidimensional scaling and neighbour-joining of multilocus genotypes indicate some bay-scale associations. However, a comparison of FST values and IBD residuals at both estuary and bay scales indicated low structure within and elevated structure among estuaries. Estuarine structuring was further supported by the presence of significant small-scale IBD within several coastal embayments (50–100 km), as well as Bayesian clustering consistent with estuarine-scale independence. Finally, estimates of dispersal based on the IBD relationship are consistent with local estuarine recruitment (<1.5 km·generation–1). We conclude that the unexpectedly high genetic structure observed is consistent with behavioral influences reducing dispersal, supporting previous work implicating active larval retention.
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Vieira, João P. "Ecological analogies between estuarine bottom trawl fish assemblages from Patos Lagoon, Rio Grande do Sul, Brazil and York River, Virginia, USA." Revista Brasileira de Zoologia 23, no. 1 (March 2006): 234–47. http://dx.doi.org/10.1590/s0101-81752006000100017.
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The structure of estuarine fish assemblages at temperate latitudes in Patos Lagoon (32º05'S, 52º04'W), Rio Grande do Sul, Brazil and York River (37º17'N, 76º33'W), Virginia, USA was compared using mid and late 1970's data from bottom trawl collection to investigate whether geographically isolated fish assemblages have similar ecological structure given similar latitudinal positions on the warmtemperate southwestern and northwestern Atlantic regions, respectively. Since estuarine species often exhibit an ontogenetic shift in habitat requirements or preferences we examined Capture per Unity of Effort by size class (CPUE-SC) and split species into "size ecological taxa" (SET) for analysis. The use of CPUE-SC also allowed the abundance of a SET to be computed by summing the mean CPUE of each size class within that SET and use this information to follows SET's temporal and or spatial abundance. A total of 65 and 63 species was collected during a year of bottom trawling in the Patos Lagoon and York River estuaries, respectively. In both localities the strongest modal size class was < 80 mm TL, and several abundant species were smaller than 100 mm TL. The size between 80 and 100 TL effectively separated several species into discrete SET's in both systems. Those SET's could have different ecological preferences, temporal and spatial distributions and so identified as different "ecological taxa". In warm months, when predation by large fish is most likely, the abundance of fish between 80 and 100 mm TL in "bottom trawl" demersal fish assemblages was low in both systems. Only the sea catfishes, in Patos Lagoon, protected by strong dorsal and pectoral spines, and the Hogchoker, in the York River, protected by burrowing in the bottom substrate, peak in abundance at this size class. The seasonal pattern of estuarine use was similar between localities and did not differ from other warm-temperate estuarine fish assemblages.
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Kisten, Yanasivan, Nadine A. Strydom, Renzo Perissinotto, and Sourav Paul. "Modelling the occurrence of postflexion stages of a marine estuarine-dependent fish in temperate South African estuaries." Scientia Marina 81, no. 1 (March 27, 2017): 27. http://dx.doi.org/10.3989/scimar.04521.05a.
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The movement of postflexion larvae of marine estuarine-dependent species into estuaries is critical for the survival of fishes reliant on estuaries as nurseries. However, detailed studies focused on environmental variability experienced by postflexion larvae entering a range of estuary types under varying conditions are rare. This study assessed the in situ conditions (temperature, salinity and water clarity) under which the southern African endemic fish Rhabdosargus holubi (Sparidae) recruits into estuaries. Postflexion larvae were sampled in three biogeographic regions (cool temperate, warm temperate and subtropical boundary), which included three estuary types (permanently open estuaries (POEs), temporarily open/closed estuaries and estuarine lake systems) on a seasonal basis, independent of each other. Rhabdosargus holubi larvae were more abundant in spring and summer, in POEs in the warm temperate region. Models predicted that higher larval occurrence in estuaries is a function of lower salinity (e.g. mesohaline zones of 5-17.9 salinity) and lower water clarity (e.g. 0-0.2 Kd, light extinction coefficient), particularly for warm, temperate POEs. This re-emphasizes the importance of freshwater for optimal nursery functioning, which may be compromised by impoundments, abstraction and climate change in water-short countries like South Africa.
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Mills, Courtenay E., Wade L. Hadwen, and Jane M. Hughes. "Looking through glassfish: marine genetic structure in an estuarine species." Marine and Freshwater Research 59, no. 7 (2008): 627. http://dx.doi.org/10.1071/mf07215.
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Through the use of mitochondrial DNA (ATP8 gene), the prediction of intermediate genetic structuring was investigated in two species of estuarine glassfish (Ambassis marianus and Ambassis jacksoniensis) (Perciformes : Ambassidae) to determine the possibility of a generalised ‘estuarine’ genetic structure. Individuals were collected from estuaries in eastern Australia between Tin Can Bay (Queensland) in the north and Kempsey (New South Wales) in the south. Analysis of the haplotype frequencies found in this region suggested panmictic populations with star-like phylogenies with extremely high levels of genetic diversity, but with no correlation between geographic distance and genetic distance. Non-significant FST and ΦST suggested extensive dispersal among estuaries. However, Tajima’s D and Fu’s FS values suggest ‘mutation–genetic drift equilibrium’ has not been reached, and that population expansions occurring 262 000 (A. marianus) and 300 000 (A. jacksoniensis) years ago may obscure any phylogeographic structuring or isolation by distance. The finding of panmixia was contrary to the prediction of genetic structuring intermediate between that of marine fish (shallowly structured) and freshwater fish (highly structured), suggesting high dispersal capabilities in these species.
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Moore, B. R., D. J. Welch, and C. A. Simpfendorfer. "Spatial patterns in the demography of a large estuarine teleost: king threadfin, Polydactylus macrochir." Marine and Freshwater Research 62, no. 8 (2011): 937. http://dx.doi.org/10.1071/mf11034.
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Understanding spatial patterns in demographic parameters of exploited fish species is of critical importance to effective fisheries management. In the present study, patterns in demography of a large, protandrous, estuarine teleost, king threadfin, Polydactylus macrochir, were compared among three estuaries on the eastern coast of Queensland, Australia. Significant variation in age and growth was observed between fish from the Fitzroy River and those from the Mary and Brisbane Rivers, with Fitzroy River fish living longer (22 years v. 10 and 14 years, respectively), reaching a greater asymptotic length (1222-mm fork length (FL) v. 975- and 1047-mm FL, respectively), and attaining greater length-at-ages of 6 years and beyond. No difference in growth was detected between Mary and Brisbane River fish, or in total mortality among any of the sites. Fitzroy River fish were generally found to mature and change sex at greater lengths and ages than those from the Mary and Brisbane Rivers. The observed variability suggests that spatially segregated populations of P. macrochir may respond differently to fishing pressure and highlights the importance of understanding the spatial patterns in demography of exploited estuarine fish populations.
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Sheaves, Marcus, Ross Johnston, and Kátya Abrantes. "Fish fauna of dry tropical and subtropical estuarine floodplain wetlands." Marine and Freshwater Research 58, no. 10 (2007): 931. http://dx.doi.org/10.1071/mf06246.
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Estuarine floodplain wetland pools occur adjacent to marine coasts and estuaries throughout the world. In Australia’s dry tropics and sub-tropics, low and irregular rainfall means estuarine wetland pools are isolated for much of the time, resulting in varied within-pool conditions, with chemistry ranging from fresh to hypersaline, depending on the balance between freshwater and marine inputs and the time between connections. Varied physical conditions and irregular connectivity provide the potential for substantial faunal difference among pools. The present study compares the compositions and structures of the fish fauna of a broad cross section of estuarine wetland pools adjacent to the estuary of the Fitzroy River, one of the largest rivers in Australia’s dry tropical/subtropical zone. Ten pools were sampled between February 2004 and May 2005. The total species richness was low, with the 6123 fish recorded over the study, comprising only 44 species. This low species richness was reflected at the individual pool level, with a maximum total richness of 25 species in a single pool. Different pools had faunas that differed as a function of the proportion of the community comprised of marine spawned, compared with freshwater spawned, species. This was a reflection of the extent of connectivity to freshwater and marine systems, which determined both the physical nature of pools and the sources of faunal supply. Despite faunal differences among pools, at a functional level pool fish faunas were dominated by detritivores, regardless of pool type, size, season or connectedness.
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Francis, Malcolm P., Mark A. Morrison, John Leathwick, and Cameron Walsh. "Predicting patterns of richness, occurrence and abundance of small fish in New Zealand estuaries." Marine and Freshwater Research 62, no. 11 (2011): 1327. http://dx.doi.org/10.1071/mf11067.
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Estuarine fish habitats are vulnerable to human impacts and are poorly studied. We surveyed 69 of New Zealand’s 443 estuaries across 1500 km to: determine species composition of small fishes; model and predict their richness, occurrence and abundance; test marine classification schemes as a basis for Marine Protected Areas; and inform impact mitigation measures. Boosted regression tree models produced acceptable fits for richness and occurrence at estuary and site scales and abundance at the site scale. Richness was greatest in northern North Island; the best predictors were estuary area and area of intertidal habitat. Within estuaries, richness increased towards the head, as water clarity declined and the substratum became muddier. Air temperature, estuary and intertidal area, tidal range and freshwater and seawater influx were the best predictors of occurrence at the estuary scale; water temperature and salinity were important at the site scale. Biological classification schemes seldom improved model fits and have little predictive utility. Richness predictions were made for 380 estuaries and occurrence predictions for 16 species. These predictions inform resource managers about estuarine fishes within their jurisdiction, bypassing the need to undertake expensive field surveys. However, sampling of environmental predictors is still required to drive some models.
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Condini, Mario V., Paula E. R. Pereyra, Alexandre M. Garcia, Tatiana D. Saint'pierre, Gianfranco Ceni, Rafael Lugo, Nelson F. Fontoura, João P. Vieira, and Cristiano Q. Albuquerque. "Use of fresh water by an estuarine-resident marine catfish: evidence from gonadal and otolith chemistry analyses." Journal of the Marine Biological Association of the United Kingdom 99, no. 7 (June 20, 2019): 1667–74. http://dx.doi.org/10.1017/s0025315419000493.
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AbstractIn this study, we examine how the Guri catfish Genidens genidens uses estuarine and freshwater habitats along the largest South American coastal lagoon, through the chemical analysis of otoliths and microscopic analysis of gonads. Chemical composition (Sr:Ca) of otolith edges allowed distinguishing between individuals who used the estuarine or freshwater compartments of the lagoon. The analysis of core-to-edge chemical profiles of each individual otolith revealed that the population may present two different patterns of habitat use along the lagoon. The ‘type 1’ pattern (89.5%) includes fish who appear to have been born in estuarine waters, whereas ‘type 2’ (9.5%) includes those fish born in fresh water. Nevertheless, juveniles from both patterns appear to migrate to estuarine waters. The gonad analysis shows G. genidens may reproduce in fresh water, as nearly 57% of all sampled fish were found to spawn in the freshwater portion of the lagoon. Also, the otolith core of many adult fish presented freshwater signatures, thus suggesting consistent fresh water use during early life. Our findings based on otolith and gonadal analyses challenge the previous classification of G. genidens as an estuarine resident. Rather, our results allow the suggestion that this species should be placed in the ‘estuarine and fresh water’ guild, which includes both fish completing their life cycles within the estuary and fish who consistently use freshwater habitats.
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Russell, D. J., and A. J. McDougall. "Movement and juvenile recruitment of mangrove jack, Lutjanus argentimaculatus (Forsskål), in northern Australia." Marine and Freshwater Research 56, no. 4 (2005): 465. http://dx.doi.org/10.1071/mf04222.
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Lutjanus argentimaculatus, tagged and released in coastal rivers and estuaries, were found to have made inter- and intra-riverine, coastal and offshore movements. A small proportion of the recaptures made offshore movements to reef habitats of up to 315 km and these recaptures were fish that were at liberty, on average, more than twice as long as those fish that had made intra-riverine movements. Most juvenile fish <400-mm length to caudal fork (LCF) resident in rivers were recaptured less than a kilometre from where they were released. The proportion of fish making sizeable movements increased with increasing recapture size, with about of 20% of larger fish (400–500-mm LCF) making offshore, inter-riverine or coastal movements. Larger fish were primarily caught offshore, whereas smaller fish <~338-mm LCF were exclusively caught in estuarine and freshwater habitats. Recruitment of juveniles into estuarine and lower freshwater riverine habitats occurred from about February. There was temporal variability of recruitment of mangrove jack into some river systems and their relative abundance within the river system was inversely proportional to the distance from the sea. Overfishing of juveniles when they are concentrated in inshore areas could have adverse implications for mangrove jack stocks.
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Becker, Alistair, Alan K. Whitfield, Paul D. Cowley, and Victoria J. Cole. "Does water depth influence size composition of estuary-associated fish? Distributions revealed using mobile acoustic-camera transects along the channel of a small shallow estuary." Marine and Freshwater Research 68, no. 11 (2017): 2163. http://dx.doi.org/10.1071/mf16230.
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Quantifying the abundance and distribution of fish is fundamental to gaining an understanding of how habitat type, water depth or abiotic conditions influence fish assemblages throughout estuarine systems. Such investigations are inherently difficult because estuaries typically contain a range of habitats across varying depth strata, and data usually consist of replicate samples that cover only a small portion of an entire estuary. We used replicate acoustic-camera (DIDSON) transects along the entire length of a small South African estuary to determine the distributions of different size cohorts of fish. Each size cohort was distributed heterogeneously along the estuary, with abundances peaking in discreet sections of the system. By comparing the abundance of fish to the bathymetry, we found correlations between depth and abundance for two of three size classes. Large fish (>401mm) were more abundant in deep holes (<3m), whereas there were more small fish (100–250mm) in shallow (>1.5m) upper reaches of the estuary. This investigation demonstrated the usefulness of extended DIDSON transects to rapidly collect data on the distributional abundance of estuarine fish from the estuary mouth to the head, showing that bathymetry of a system may be an important factor in determining these patterns.
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Bacheler, Nathan M., Jeffrey A. Buckel, and Lee M. Paramore. "Density-dependent habitat use and growth of an estuarine fish." Canadian Journal of Fisheries and Aquatic Sciences 69, no. 11 (November 2012): 1734–47. http://dx.doi.org/10.1139/f2012-098.
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Density dependence can stabilize or destabilize population size through negative or positive feedback controls operating over different spatial and temporal scales. While many species have been shown to exhibit density dependence, the topic has received little attention in estuaries where environmental variability and larval supply are often considered to be the primary drivers of population dynamics. We used multiple long-term, fishery-independent data sets and a unique modeling approach to test the hypothesis that juvenile red drum ( Sciaenops ocellatus ) exhibit density-dependent habitat use and growth rates in estuaries in North Carolina, USA. Age-1 red drum exhibited density-dependent habitat use after accounting for environmental and landscape variables, disproportionately increasing northward and coastward in the study area at high abundance. Apparent individual growth rates of age-0 and age-1 red drum were generally negatively related to the abundance of their own age classes, but evidence of density-dependent growth rates for age-2 red drum was weak to nonexistent. Changes in spatial distribution of red drum when overall abundance was high did not overcome density-dependent effects on individual growth rates. Thus, density-dependent effects have potential negative feedbacks on population growth in estuaries and should not be ignored in future theoretical or empirical estuarine studies.
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Henderson, P. A. "The structure of estuarine fish communities." Journal of Fish Biology 33, sa (December 1988): 223–25. http://dx.doi.org/10.1111/j.1095-8649.1988.tb05577.x.
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Claridge, P. N., I. C. Potter, and M. W. Hardisty. "Seasonal Changes in Movements, Abundance, Size Composition and Diversity of the Fish Fauna of the Severn Estuary." Journal of the Marine Biological Association of the United Kingdom 66, no. 1 (February 1986): 229–58. http://dx.doi.org/10.1017/s002531540003976x.
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Estuaries perform a crucial role in the life-cycle of many fish (Cronin & Mansueti, 1971; Day, Blaber & Wallace, 1981; Dando, 1984). They provide a migratory route for anadromous and catadromous species and an environment in which the limited number of true estuarine teleosts spend the whole of their life cycle. The upper reaches are colonized by certain freshwater species while the lower regions are penetrated by some marine fish during high tide. However, many marine teleosts enter and remain within estuaries for a period of time, often in very large numbers and particularly during the early part of life (see e.g. Gunter, 1938, 1961, 1967; Huddart & Arthur, 1971; van den Broek, 1980; Blaber & Blaber, 1980; Potter et al. 1983; Whitfield, 1983). The recognition that estuaries act as important nursery areas for certain teleosts by providing such features as a rich food source and protection from predation (see e.g. Pearcy & Richards, 1962] Jacquaz, Able & Leggett, 1977; Blaber & Blaber, 1980) has led to such species being referred to as estuarine-dependent (see e.g. McHugh, 1976; Beal, 1980; Fortier & Leggett, 1982).
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Selleslagh, Jonathan, Sandric Lesourd, and Rachid Amara. "Comparison of macrobenthic assemblages of three fish estuarine nurseries and their importance as foraging grounds." Journal of the Marine Biological Association of the United Kingdom 92, no. 1 (April 7, 2011): 85–97. http://dx.doi.org/10.1017/s0025315411000336.
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Macrobenthic assemblages were examined in three fish estuarine nurseries and related to environmental variables, as well as fish and macrocrustaceans, in order to assess and compare the potential foraging ground value of these systems. Macrobenthos was sampled in spring 2007 in the Canche, Authie and Somme estuaries (eastern English Channel, France). A total of 17, 28 and 23 macrobenthic taxa, with a clear dominance of amphipods (mainly Bathyporeia sarsi), polychaetes and bivalves, were recorded in the three estuaries respectively. Although predators (fish and macrocrustaceans) were abundant, relatively high densities of macrobenthos were observed: 876.2 ± 389.1, 595.4 ± 197.2 and 854.3 ± 281.2 ind. m-2 in the Canche, Authie and Somme, respectively. No significant difference in species richness, Shannon–Wiener diversity and density (total and dominant groups) of macrobenthos was observed between the three estuaries. Although the analysis of similarity and similarity percentages analyses indicated that macrobenthic assemblage was variable between Authie and Somme, results showed that macrobenthos resource was relatively high and similar in the three estuaries. Taking into account these considerations, the present study indicated a similar relative importance of the Canche, Authie and Somme estuaries as foraging grounds for fish and macrocrustaceans during spring. Multivariate analysis showed that macrobenthic assemblages were mainly driven by salinity and sediment characteristics in the Canche and Authie estuaries while in the Somme estuary sediment characteristics were the most influencing parameters.
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Mariano-Jelicich, Rocío, Germán García, and Marco Favero. "Fish composition and prey utilization of the black skimmer (Rynchops niger) in mar Chiquita coastal lagoon, Argentina." Brazilian Journal of Oceanography 62, no. 1 (March 2014): 1–10. http://dx.doi.org/10.1590/s1679-87592014034806201.
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Lagoons along the western coast of the South Atlantic Ocean shelter high densities of juvenile fish and are key areas for several seabirds that rely on the resources offered by this kind of ecosystem. The objective of this study was to analyze fish composition and abundance in shallow-water areas of the estuarine region of Mar Chiquita Coastal Lagoon (Argentina) and the diet composition of the Black skimmer (Rynchops niger) during its non-breeding season as well as evaluating its inter-annual variations. Fish were sampled with a beach-seine net and the skimmers' diet was analyzed from their pellets. The estuarine-dependent marine fishes were the best represented bio-ecological category followed by freshwater fishes. Significant differences were observed in fish abundance and composition between and within years. Species richness was higher during the summer season and during the first year sampled. The occurrence of freshwater fishes as an important and diverse group of the Mar Chiquita estuarine area contrasted with previous reports. The diet of the Black skimmer included freshwater, estuarine and marine fish species. Skimmers forage in the shallow waters of the estuarine area of the Mar Chiquita Coastal lagoon though little similarity was observed between its diet and local fish abundance. These results emphasize the importance of performing these evaluations in order to improve the quality of studies and the interpretations of top predators foraging ecology.
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Kumaraguru, Arumugam, Rosette Celsiya Mary, and Vijayaraghavalu Saisaraswathi. "A review about fish walking on land." Journal of Threatened Taxa 12, no. 17 (December 26, 2020): 17276–86. http://dx.doi.org/10.11609/jott.6243.12.17.17276-17286.
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Mudskippers are amphibious species inhabiting semi-terrestrial ecosystems like mudflats, mangroves, marshy swamps, intertidal regions, and estuaries. Around 34 diversified species are found across the globe. Mudskipper belongs to the Oxudercidae family and the subfamily is Oxudercinae. The occurrence of species is vastly found across the Indo-West Pacific region, the tropical western coast of Africa and in the Indian Ocean. Mudskippers are known for being the biological indicator and also an indicator of estuarine safety monitoring. They are used by people for prey-catching baits. This review paper explains the ecological indicators, taxonomy, species diversity, habitat, behavioural pattern, respiration & kinematics, feeding ecology, reproduction, nutrition content & its medicinal value, and threats to mudskippers.
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Passos, Ana Carolina dos, Riguel Feltrin Contente, Ciro Colodetti Vilar de Araujo, Felippe Alexandre Lisboa de Miranda Daros, Henry Louis Spach, Vinícius Abilhôa, and Luis Fernando Fávaro. "Fishes of Paranaguá Estuarine Complex, South West Atlantic." Biota Neotropica 12, no. 3 (September 2012): 226–38. http://dx.doi.org/10.1590/s1676-06032012000300022.
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The objective of this work was to present an updated checklist of the currently known fishes in the Paranaguá Estuarine Complex (PEC) and provides comments on conservation status for the treated species. We used a large dataset derived from a pool of studies which have been conducted within there along the last 30 years. Each study was based on monthly samplings and conducted in several estuarine habitat; thus, the pool covers practically all estuarine habitats and takes into account the seasonal cycle in the system. The PEC ichthyofauna represents a mixture between that fauna typical from the tropical Brazilian coast and that with affinities of temperate Argentinean and Uruguayan zones. The PEC harbors a rich fish fauna of 213 species, inserted in the families that are common along the Brazilian coast. Only a minor part (8%) of the PEC fish fauna was evaluated as regards the conservation status, mostly because of the lack of basic biological and ecological information for most species. Despite part of the among-estuaries differences are due to different and incomplete sampling efforts, the richness in the PEC is surprisingly higher than other systems in Brazil and around world, which emphasize the importance of the region for global biodiversity conservation.
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Smith, Kimberley A., and Iain M. Suthers. "Consistent timing of juvenile fish recruitment to seagrass beds within two Sydney estuaries." Marine and Freshwater Research 51, no. 8 (2000): 765. http://dx.doi.org/10.1071/mf99142.
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Recruitment patterns of juvenile Rhabdosargus sarba (Sparidae) and Pelates sexlineatus (Terapontidae) were examined by frequent (1–4 weeks) beach seining of seagrass beds in Sydney, south-east Australia. Two sites within each of two estuaries (Botany Bay and Pitt Water) were sampled for one year. One site within Botany Bay was sampled for 3 years. A total of 12 824 juveniles of R. sarba and 7037 juveniles of P. sexlineatus were collected. R. sarba recruited in 4 pulses during winter/spring, while P. sexlineatus recruited in 6 pulses during summer/autumn, and the timing of recruitment events was consistent among locations and years. P. sexlineatus recruitment coincided with new moons, but R. sarba recruitment dates were less precisely determined. Predictable annual recruitment patterns result in temporal partitioning of seagrass habitat between these two abundant estuarine species. Spatial differences in magnitude of recruitment events among sites reflected patterns of estuarine circulation.
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Park, Joo Myun, Ralf Riedel, Hyun Hee Ju, and Hee Chan Choi. "Fish Assemblage Structure Comparison between Freshwater and Estuarine Habitats in the Lower Nakdong River, South Korea." Journal of Marine Science and Engineering 8, no. 7 (July 5, 2020): 496. http://dx.doi.org/10.3390/jmse8070496.
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Variabilities of biological communities in lower reaches of urban river systems are highly influenced by artificial constructions, alterations of flow regimes and episodic weather events. Impacts of estuary weirs on fish assemblages are particularly distinct because the weirs are disturbed in linking between freshwater and estuarine fish communities, and migration successes for regional fish fauna. This study conducted fish sampling at the lower reaches of the Nakdong River to assess spatio-temporal variations in fish assemblages, and effects of estuary weir on structuring fish assemblage between freshwater and estuary habitats. In total, 20,386 specimens comprising 78 species and 41 families were collected. The numerical dominant fish species were Tachysurus nitidus (48.8% in total abundance), Hemibarbus labeo (10.7%) and Chanodichthys erythropterus (3.6%) in the freshwater region, and Engraulis japonicus (10.0%), Nuchequula nuchalis (7.7%) and Clupea pallasii (5.2%) in the estuarine site. The fish sampled were primarily small species or the juveniles of larger species at the estuary region, while all life stages of fishes were observed at the freshwater habitats. The diversity patterns of fish assemblages varied greatly according to study site and season, with higher trends at estuarine sites during the warm-rainy season. No significant difference in diversity between freshwater and estuarine sites during the cold-dry season were found. Multivariate analyses of fish assemblage showed spatial and seasonal differences of assemblage structures. Higher effects of between-site variability but not within seasonal variability at each site were observed. Variations in assemblage structures were due to different contributions of dominant species in each habitat. Common freshwater species characterized the fish assemblage in the freshwater region, while marine juveniles were significantly associated with the estuarine habitat. The results from the ecological guild analyses showed distinct ecological roles for freshwater and marine species, and overlapping roles for fish sampled at the fishways. The lower reaches of the Nakdong River are an important ecosystem for both freshwater and marine juveniles. Nakdong River estuarine residents and migrant fishes, however, have been negatively affected by the construction of the weir (gravity dam), due to the obstruction to migration from and to freshwater habitats. Conservation and management policies aimed at minimizing anthropogenic influences on estuary ecosystems should focus on evaluating ecological functions of estuary weirs.
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Charpentier, Corie L., Christopher S. Angell, Patrick I. Duffy, and Jonathan H. Cohen. "Natural variations in estuarine fish, fish odor, and zooplankton photobehavior." Marine and Freshwater Behaviour and Physiology 52, no. 6 (November 2, 2019): 265–82. http://dx.doi.org/10.1080/10236244.2020.1713701.
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Halliday, Ian A., Julie B. Robins, David G. Mayer, Jonathan Staunton-Smith, and Michelle J. Sellin. "Effects of freshwater flow on the year-class strength of a non-diadromous estuarine finfish, king threadfin (Polydactylus macrochir), in a dry-tropical estuary." Marine and Freshwater Research 59, no. 2 (2008): 157. http://dx.doi.org/10.1071/mf07077.
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The year-class strength of the commercial catch of king threadfin (Polydactylus macrochir (Gunther, 1876)) was correlated with freshwater flows into a dry-tropical estuary over five consecutive years. The year-class strength of king threadfin, a non-diadromous estuarine species, fluctuated and correlated significantly with freshwater flow and coastal rainfall in spring and summer; a result similar to that found for the catadromous barramundi (Lates calcarifer) within the same estuarine system. All sub-sets general linear models were used to screen relationships between year-class strength and freshwater variables. King threadfin spawn from spring to summer in north-eastern Australia, when hydrological conditions adjacent to estuaries have high salinities and are optimal for egg and post-larval survival. Young-of-the-year enter estuaries during the wet season, enabling them to take advantage of salinity gradients and the seasonal blooms in prey species such as Acetes spp. and juvenile penaeids that are accentuated in wet years. Freshwater flows in spring and summer are important drivers of the year-class strength of estuarine finfish, and reduction in these flows, through the development of water infrastructure and abstraction or long-term climate change, will potentially reduce the size of the population of estuarine fish available for human harvest.
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Levings, C. D., N. A. Hvidsten, and B. Ø. Johnsen. "Feeding of Atlantic salmon (Salmo salar L.) postsmolts in a fjord in central Norway." Canadian Journal of Zoology 72, no. 5 (May 1, 1994): 834–39. http://dx.doi.org/10.1139/z94-113.
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The feeding habits of postsmolt Atlantic salmon (Salmo salar) caught by two-boat trawling were studied in Trondheimsfjord in central Norway. Fish caught in the inner fjord near the estuaries of the Orkla and Gaula rivers had recently fed on food produced in freshwater and estuarine habitats, namely stonefly and mayfly nymphs and gammarid amphipods. Stomach contents of postsmolts caught farther seaward were dominated by adult insects, with smaller proportions of the food volume originating from marine pelagic (larval fish, hyperiid amphipods, calanoid copepods) and nearshore (gammarid amphipods) habitats.
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Hadwen, Wade L., Grant L. Russell, and Angela H. Arthington. "Gut content- and stable isotope-derived diets of four commercially and recreationally important fish species in two intermittently open estuaries." Marine and Freshwater Research 58, no. 4 (2007): 363. http://dx.doi.org/10.1071/mf06157.
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Despite remaining closed for variable periods, intermittently open estuaries provide habitat for estuarine and marine fish species of commercial and recreational value. To better understand how these systems trophically support their fish assemblages, the diets of four valued fish species, namely Acanthopagrus australis, Platycephalus fuscus, Sillago ciliata and Mugil cephalus, were examined in two intermittently open estuaries in New South Wales, Australia. Fish diets were determined using both gut contents and stable isotope analyses because the different temporal resolutions afforded by these methods can provide insight into the flexibility of fish diets. Stable isotope signatures of prey and fish proved to be particularly useful in analyses of the diets of M. cephalus and P. fuscus, because these species consume large quantities of unidentifiable organic matter and have high incidences of empty guts respectively. Diet reconstructions across methods were generally consistent for A. australis, but differed substantially for S. ciliata, with fewer prey taxa identified in the guts than expected. This result suggests that individual S. ciliata switch between local resources on the basis of their fluctuating temporal availability. Trophic flexibility, coupled with broad physicochemical tolerances, enables these species to flourish in the challenging environment of intermittently open estuaries.
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McGregor, Steven, and Nadine A. Strydom. "The abundance, diversity and distribution of small fishes in mangrove and non-mangrove estuaries in warm temperate South Africa." Scientia Marina 82, no. 2 (July 6, 2018): 81. http://dx.doi.org/10.3989/scimar.04744.31a.
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Mangroves in tropical and subtropical regions have been well documented in terms of the advantages they provide and their role in structuring ichthyofaunal assemblages, but little is known about their warm temperate counterparts. The study aimed to investigate the importance of warm temperate mangroves by comparing the abundance, diversity and distribution of small fishes in mangrove and non-mangrove estuaries in warm temperate South Africa. A 50x2 m (12-mm mesh) seine net was used over three summer seasons to sample small fishes in the Gonubie, Qora, Nahoon and Xhora estuaries (the latter two being mangrove estuaries). Fish abundance and diversity showed little variation among estuaries, despite the presence of mangroves. Estuaries in warm temperate areas are not only at the edge of mangrove distribution, but also offer alternative habitats which lend similar advantages to fish survival. It appears that warm temperate ichthyofauna have not yet evolved a dependence on mangrove systems in terms of the food, refuge and other ecological services they provide. Understanding the function of habitats and their value in enhancing fish survival in estuarine nursery areas is essential for fish conservation.
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Toledo, Pamela, Audrey M. Darnaude, Edwin J. Niklitschek, Vilma Ojeda, Raphaël Voué, Félix P. Leiva, Maylis Labonne, and Cristian B. Canales-Aguirre. "Partial migration and early size of southern hake Merluccius australis: a journey between estuarine and oceanic habitats off Northwest Patagonia." ICES Journal of Marine Science 76, no. 4 (December 6, 2018): 1094–106. http://dx.doi.org/10.1093/icesjms/fsy170.
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Abstract Partial migration is a key adaptive strategy, increasingly observed across multiple taxa. To investigate partial migration and life-cycle diversity of Merluccius australis in northwestern Patagonia, we analysed isotopic (δ13C, δ18O) and elemental (11B, 23Na, 24 Mg, 55Mn, 86Sr, 138Ba) compositions of otoliths from juveniles, sub-adults, and adults to identify nursery origins, habitats used, and migratory behaviours of multiple cohorts (1990–2005). Influence of early size upon migration was assessed by comparing back-calculated sizes at demersal recruitment between resident and migratory adults. Although partial migration occurred at both estuarine and oceanic nursery habitats, migratory behaviour was more frequent in fish of estuarine origin (59%) than in fish of oceanic origin (17%). Adults of estuarine origin dominated both estuarine (92%) and oceanic (77%) sampling areas. Although we found no significant differences in size at demersal recruitment between oceanic-resident and oceanic-migratory fish, a strong relationship between size at demersal recruitment and migratory behaviour appeared in fish of estuarine origin, whose probability of migration increased from 5% to 95% as demersal recruitment size increased from 18.8 to 23.6 cm. Further research on M. australis life cycle is required to incorporate sub-population processes into the stock assessment and management models being used for this overexploited species.
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Macdonald, J. Stevenson, Colin D. Levings, Carey D. McAllister, U. H. M. Fagerlund, and J. R. McBride. "A Field Experiment to Test the Importance of Estuaries for Chinook Salmon (Oncorhynchus tshawytscha) Survival: Short-Term Results." Canadian Journal of Fisheries and Aquatic Sciences 45, no. 8 (August 1, 1988): 1366–77. http://dx.doi.org/10.1139/f88-160.
Full textAbstract:
In late April of 1983, 1984, and 1985, 140 000 marked chinook salmon (Oncorhynchus tshawytscha) smolts (2–4 g) were transported by helicopter from Quinsam Hatchery to four release sites near Campbell River, B.C. (river, estuarine, transition, and marine), in an experiment to test the importance of estuarine residency to chinook survival. At the marine site, fish were released directly into seawater. These fish had high cortisol levels and larger interrenal nuclear diameters than those at the estuarine site, indicating a transitory stress response to seawater exposure. Nevertheless, there was little direct mortality due to stress or osmoregulatory shock at any of the release sites. Marine-released fish were exposed to more bird and fish predators. Mortality of caged chinook was higher at the marine location than at all other sites despite seawater challenge tests indicating that the chinook were smolted and "ready for sea." Beach seine data obtained biweekly for 4 mo after the releases showed that fish released directly into marine waters rarely dispersed to the Campbell River estuary. Fish released immediately adjacent to the mouth of the estuary (transition zone) had the widest immediate dispersal pattern, with many of them returning to the estuary. Estuarine zone fish displayed the most restricted distribution. Fish released to the river and estuary remained in the sampling area for a longer period (34–47 d) than those released in the marine or transition zone (20–23 d).
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Newton, GM. "Estuarine Ichthyoplankton Ecology in Relation to Hydrology and Zooplankton Dynamics in salt-wedge Estuary." Marine and Freshwater Research 47, no. 2 (1996): 99. http://dx.doi.org/10.1071/mf9960099.
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The ichthyoplankton assemblage of the Hopkins River estuary, Victoria, was dominated by estuarine taxa that included demersal (goby, gudgeon) and pelagic (black bream, estuary perch, anchovy) species. The two seasonal peaks in fish larvae abundance were related to (1) the spring/summer zooplankton increase that occurred after flooding of the estuary and was comprised predominantly of copepod nauplii, thereby providing a good prey field for very young fish larvae, and (2) the autumn zooplankton maxima, which would provide a wide selection of copepod stages and meroplankton and promote dietary partitioning and flexibility among older larval stages. The two peaks in fish larvae abundance occurred well before and well after the attainment of maximum water temperature in the estuary. Goby, gudgeon, estuary perch and anchovy larvae were in the plankton over an extended period coinciding with the more stable conditions of salt-wedge presence and maximum zooplankton densities. The spawning of black bream and anchovies in the estuary was clearly related to physical conditions, such as salinity and water temperature, and habitat-although spawning of both species also occurred at times of high concentrations of potential prey organisms for their larvae. Adults of all the above fish species appear to have evolved spawning strategies that are adapted to the average hydrological and biological conditions in the estuary that would lead to the enhanced survival of their larvae. With the exception of the black bream, it appears that a ubiquitous and prolonged rather than a synchronous and confined spawning strategy is more widely used by estuarine-spawning fishes in the Hopkins River estuary. This type of spawning strategy, combined with the generally high density of food available to fish larvae in estuaries, suggests that the match-mismatch hypothesis of Cushing may be less relevant in the estuarine than in the marine environment.
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Baptista, Joana, Filipe Martinho, Marina Dolbeth, Ivan Viegas, Henrique Cabral, and Miguel Pardal. "Effects of freshwater flow on the fish assemblage of the Mondego estuary (Portugal): comparison between drought and non-drought years." Marine and Freshwater Research 61, no. 4 (2010): 490. http://dx.doi.org/10.1071/mf09174.
Full textAbstract:
Warming of the planet is indisputable and will lead to more frequent extreme events, such as droughts. From June 2003 to March 2008, the effects of variations in river flow, associated with drought conditions, were studied in the fish assemblage of the Mondego estuary, Portugal. Over this time, two distinct hydrological periods were identified: non-drought years and drought years, with consistent changes in the fish assemblages. In the drought years, salinity increased inside the estuary, displacing the estuarine brackish habitats to more upstream areas. During this period, new marine adventitious species were found mainly in the most downstream areas, while the freshwater species disappeared from the Mondego estuary catchment area. For the marine estuarine-dependent species that use estuaries as nursery areas, a decrease in abundance was observed during the drought years, owing to the decrease in freshwater flow and reduced river plume to the coastal area. In non-drought years, there were higher densities of most species and the more important species of the fish community. Our work shows that extreme events such as droughts, related to climatic changes, influenced the structure and composition of the Mondego estuary fish assemblages, and should be further considered when undertaking management plans for transitional waters.
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Polivka, Karl M. "Responses to the Foraging/Predation Risk Trade-Off and Individual Variability in Population-Level Fitness Correlates." ISRN Ecology 2011 (June 7, 2011): 1–8. http://dx.doi.org/10.5402/2011/376083.
Full textAbstract:
Foraging under the influence of interspecific interactions such as competition and predation risk can have effects on the energetic reserves of the forager. Measurements of condition in species such as fish are usually correlated with individual fecundity and, hence, fitness. From work in two study systems in which predation risk regulates habitat selection and foraging behavior of benthic fishes I examined whether risk dependence led to reduced variability in fish condition. In field populations of cottid fishes, observed in an estuarine system and in the near-shore habitat of an oligotrophic lake, I found that individuals that experienced higher predation risk showed reduced variability in CI. Estuarine cottids with high food availability and substantial predation risk varied less in CI among individuals than in the associated tidal creek. In the lake, where there is considerable heterogeneity in benthic food resources, a related cottid species showed reduced variation in CI with increasing predation risk from adults. Finally, I examine my previous experiments showing that the estuarine species is limited in its use of high resource availability in estuaries by competition and predation risk. Here I found that variability in individual condition index (CI) was higher when intraspecific and interspecific competition increased and did not increase in the face of predation risk.
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Waugh, A., M. Elliot, and A. Franco. "Debunking paradigms in estuarine fish species richness." Marine Ecology Progress Series 613 (March 21, 2019): 125–38. http://dx.doi.org/10.3354/meps12883.
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Branco, Paulo, José Lino Costa, and Pedro Raposo de Almeida. "Conservation Priority Index for Estuarine Fish (COPIEF)." Estuarine, Coastal and Shelf Science 80, no. 4 (December 2008): 581–88. http://dx.doi.org/10.1016/j.ecss.2008.09.015.
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Elsdon, Travis S., and Bronwyn M. Gillanders. "Alternative life-history patterns of estuarine fish: barium in otoliths elucidates freshwater residency." Canadian Journal of Fisheries and Aquatic Sciences 62, no. 5 (May 1, 2005): 1143–52. http://dx.doi.org/10.1139/f05-029.
Full textAbstract:
Elemental concentrations in fish otoliths (earstones) can reconstruct environmental histories of fish if predictable relationships between the environment and elemental incorporation are established. We assessed whether fresh water occupancy of black bream (Acanthopagrus butcheri) can be inferred from otolith barium concentrations (Ba was standardized to calcium (Ca) and expressed as a ratio, Ba:Ca). Otolith Ba:Ca of fish was correlated with ambient Ba:Ca. Using the natural relationships of increasing ambient and otolith Ba:Ca with decreasing salinity, fish from fresh- and salt-water environments were distinguishable. Fish caught in fresh water had approximately double the otolith Ba:Ca of those from salt-water estuaries, for both summer and winter collections. Fish with otolith Ba:Ca ≤5 µmol·mol1 were classified as resident in salt water, and those with ≥6 µmol·mol1 as resident in fresh water. Transects of Ba:Ca across fish otoliths classified fish to fresh- or salt-water environments. Fish were identified as having migratory patterns typical of residents, migrants with irregular patterns of diadromy, or migrants with cyclic patterns of anadromomy. Multiple migratory behaviours occurred in fish from the same estuary, indicating far more complex migratory behaviours than were previously known. The application of otolith Ba:Ca to infer freshwater occupancy of fish has rarely been studied, yet may provide more accurate classifications of estuarine environments than strontium (Sr) isotopes and otolith Sr:Ca.