Tesi: "Freshwater fishes"

1

Kontula, Tytti. "Phylogeography and evolution of freshwater cottid fishes". Helsinki : University of Helsinki, 2003. http://ethesis.helsinki.fi/julkaisut/mat/ekolo/vk/kontula/.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

2

Khan, Tariq. "Exotic fish impacts on lake community structure and function in Western Victoria, Australia". Thesis, Federation University Australia, 2002. http://researchonline.federation.edu.au/vital/access/HandleResolver/1959.17/164899.

Testo completo

Abstract (sommario):

The researcher investigated a number of closed catchment lakes in western Victoria that have been stocked with exotic fish. Exotic-native fish interactions were studied and the potential of the exotic species to affect the lake ecosystem structure was explored.
Doctor of Philosophy

Gli stili APA, Harvard, Vancouver, ISO e altri

3

Miller, Peggy E. "Diagnosis, prevalence, and prevention of the spread of the parasite Heterosporis sp. (Microsporida: Pleistophoridae) in yellow perch (Perca flavescens) and other freshwater fish in northern Minnesota, Wisconsin, and in Lake Ontario /". Connect to online version, 2009. http://minds.wisconsin.edu/handle/1793/37972.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

4

Fogelström, Anna. "DNA barcoding of freshwater fishes in Matang, Malaysia". Thesis, Uppsala universitet, Institutionen för biologisk grundutbildning, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-255333.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

5

Heath, Daniel D. "An experimental and theoretical investigation of stunting in freshwater fish /". Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=65985.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

6

Carden, Kerilynn M. "Macrophytes as fish habitat : the role of macrophyte morphology and bed complexity in fish species distributions /". Link to abstract, 2002. http://epapers.uwsp.edu/abstracts/2002/Carden.pdf.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

7

Ozburn, Nicholas R. "Influence of dams on stream fish biodiversity across a diverse Georgia landscape". Auburn, Ala., 2007. http://repo.lib.auburn.edu/07M%20Theses/OZBURN_NICHOLAS_54.pdf.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

8

O'Connell, Martin T. "Immunological responses of fishes to glochidia of freshwater mussels". Thesis, Virginia Tech, 1991. http://hdl.handle.net/10919/41705.

Testo completo

Abstract (sommario):

The immunological aspects of the interaction between fish and glochidia were studied using glochidia of the Alabama rainbow mussel (Villosa iris). Tested host species was the rock bass (Ambloplites rupestris) and non-host fishes were common carp (Cyprinus carpio) and goldfish (Carassius auratus). Ouchterlony double-diffusion tests showed that both the host and non-host species expressed a specific humoral response to glochidial antigens after being artificially infested with the parasites. Further microagglutination tests were completed to compare titers of host and non-host fishes which were either uninfested, infested, or reinfested with glochidia. These tests showed that host and non-host species exhibit humoral responses of similar strengths (similar titers) to glochidia. In addition, fishes infested with glochidia had higher titers than uninfested fishes, and reinfested fishes had titers higher than both uninfested and infested fishes. Results indicate that fishes express anamnestic responses to glochidia. Because many host-specific parasites mimic their host’s antigens to avoid full immune attack, I tested for antigen mimicry in glochidia. Goldfish were injected with host (rock bass) and non-host (carp) antigens, in the form of sera, and then re-exposed to glochidial antigens at a later time. This test and other experimental results show no evidence of mimicry of host antigens by glochidia before attachment to host fish. Immunoelectrophoresis (IEP) was used to compare precipitation patterns of host and non-host fishes and to determine whether IEP can be used for identifying suitable hosts for a species of mussel. Although there were subtle differences observed between the precipitation bands of host and non-host fishes using IEP, successful molecular host identification will require more precise electrophoretic methods. The precipitation patterns of glochidial antigens and transformed juvenile antigens (reacted with anti-glochidia fish anti-sera) were compared to determine whether glochidia develop new antigens to avoid a full immune attack during glochidiosis. No precipitation occurred in trials using transformed juvenile antigens; therefore, pre-infestation glochidia and post-infestation juvenile mussels are antigenically different.
Master of Science

Gli stili APA, Harvard, Vancouver, ISO e altri

9

Ross, Jason. "An investigation of the distribution patterns of aquatic vertebrates across four sites in the upper Parramatta River catchment /". View thesis View thesis, 2000. http://library.uws.edu.au/adt-NUWS/public/adt-NUWS20030429.115844/index.html.

Testo completo

Abstract (sommario):

Thesis (M.Sc. (Hons.)) -- University of Western Sydney, 2000.
"A thesis submitted in part-fulfilment of the requirements for the degree of Master of Science (Honours)" Bibliography : leaves 131-152.

Gli stili APA, Harvard, Vancouver, ISO e altri

10

Hassan, Marina. "Parasites of native and exotic freshwater fishes in the south-west of Western Australia". Thesis, Hassan, Marina (2008) Parasites of native and exotic freshwater fishes in the south-west of Western Australia. PhD thesis, Murdoch University, 2008. https://researchrepository.murdoch.edu.au/id/eprint/704/.

Testo completo

Abstract (sommario):

Fewer than 200 fish species are found in freshwater habitats in Australia, of which 144 are confined exclusively to freshwater. At least 22 species of exotic freshwater fish have been introduced into Australia, and 19 of these have established self-sustaining populations. However, the parasite fauna of both native and exotic freshwater fishes in Australia is poorly known. This is particularly the case in the south-west of Western Australia, where there have been no previous comprehensive studies of the parasites of 14 native species and nine or more exotic species of fish found in freshwater habitats. This study represents a survey of the parasites of freshwater fishes in the South West Coast Drainage Division and reports 44 putative species of parasites in 1429 individual fishes of 18 different species (12 native and six exotic) from 29 locations. Parasites were found in 327 (22.88%) fishes, and of the infected fishes, 200 (61.16%) were infected with only one species of parasite and 127 (38.84%) were infected with two or more species of parasites. For helminth and arthropod parasites, which were more comprehensively surveyed than protozoan and myxozoans, I found 37 species compared to 77 species found in a recent study of fishes from the East Coast Drainage Division. The present study demonstrated that parasitic infection was significantly more common in native fish species (mean prevalence of infection with any species of parasite = 0.36 ± 0.09) than in exotic fish species (0.01 ± 0.12). Parasites were found in all native fish species, but in only two exotic fish species that were examined. Parasite regional and component community diversity were estimated by species richness (the number of species, S) and by an index of taxonomic diversity (HT). Both parasite species richness and parasite taxonomic diversity were significantly greater in native fish species (mean S = 10.5 ± 2.3; mean HT = 1.19 ± 0.14) than in exotic fish species (mean S = 1.6 ± 3.3; mean HT = 0.27 ± 0.20). These relationships were consistent over all geographic locations that were sampled. The reduced parasite load of exotic species compared to native species has been previous reported across a wide range of taxa. It is thought to arise partly because founding populations of hosts have a low probability of harbouring the species’ total parasite fauna, and partly because parasites that infect introduced exotic species may not be able to maintain their life cycle in the new environment. It has been suggested that a reduced parasite load increases the competitive ability of exotic species compared to native species (the parasite release hypothesis) and this may partly explain the abundance and apparent competitive success of exotic over native species of freshwater fish in the South West Coast Drainage Division. For native species of fish, there were major differences among species in both prevalence of parasitic infection and parasite community diversity, but this variation was not related to fish size, whether the fish were primarily freshwater or primarily estuarine, or whether they were primarily demersal or pelagic. In this study, I report two new parasites in south western Australian waters. Both are copepod parasites; Lernaea cyprinacea and a new species of Dermoergasilus. The Dermoergasilus appears to be native to the south-west of Western Australia and has been described as Dermoergasilus westernensis. It differs from previously described species in the genus principally by the armature of the legs. This new species was found on the gills of freshwater cobbler, Tandanus bostocki and western minnow, Galaxias occidentalis in two different river systems. Lernaea cyprinacea is an introduced parasitic copepod found on the skin and gills of freshwater fishes in many areas of the world. The parasite has not previously been reported in Western Australia. We found infestations of L. cyprinacea on four native fish species (G. occidentalis; Edelia vittata; Bostockia porosa; T. bostocki) and three introduced fish species (Carassius auratus; Gambusia holbrooki; Phalloceros caudimaculatus) at two localities in the Canning River, in the south-west of Western Australia. The parasite has the potential to have serious pathogenic effects on native fish species, although it appears to be currently localised to a small section of the Canning River. Over all localities from which fishes were sampled in the present study, the proportion of native freshwater fishes with parasitic infections and the component community diversity of the parasite fauna of native fishes were both negatively related to habitat disturbance, in particular to a suite of factors (river regulation, loss of riparian vegetation, eutrophication and presence of exotic fish species) that indicate increased human usage of the river and surrounding environment. The reduced parasite load and diversity in native fishes from south-west rivers with greater human usage was due principally to the loss of a number of species of trematode, cestode and nematode endoparasites which use fishes as intermediate hosts. Other studies have also found that endoparasites with complex life cycles are most likely to be adversely affected by environmental changes, presumably because any environmental changes which impact on either free-living parasite stages or on any of the hosts in the complex train of parasite transmission will reduce parasite population size and may cause local extinction of the parasite species. The most heavily infected species of native freshwater fish in the South West Coast Drainage Division was T. bostocki with 96% of all individuals containing at least one species of parasite. As with most freshwater fishes of south-west Australia, T. bostocki is limited in its distribution to waterways with relatively low salinity. The degree of parasitism and histopathology of internal and external organs in T. bostocki from the Blackwood River was examined over a period of rapid, seasonal changes in water salinity. As salinity increased, the infracommunity richness and prevalence of ectoparasites on the skin of fishes decreased, while the infracommunity richness and prevalence of endoparasites increased. This was associated with a decrease in histopathological lesion scores in the skin and an increase in histopathological lesion scores in internal organs, particularly the intestine. I hypothesise that the seasonal spike in salinity had two contrasting effects on parasitic infections of T. bostocki. Firstly, it increased the mortality rate of parasites directly exposed to water, leading to a decrease in ectoparasitic infection and associated pathology. Secondly, it suppressed immune function in fish, leading to a decreased mortality rate of parasites not directly exposed to water and a more severe pathological response to endoparasitism.

Gli stili APA, Harvard, Vancouver, ISO e altri

11

Hassan, Marina. "Parasites of native and exotic freshwater fishes in the South-West of Western Australia /". Hassan, Marina (2008) Parasites of native and exotic freshwater fishes in the south-west of Western Australia. PhD thesis, Murdoch University, 2008. http://researchrepository.murdoch.edu.au/704/.

Testo completo

Abstract (sommario):

Fewer than 200 fish species are found in freshwater habitats in Australia, of which 144 are confined exclusively to freshwater. At least 22 species of exotic freshwater fish have been introduced into Australia, and 19 of these have established self-sustaining populations. However, the parasite fauna of both native and exotic freshwater fishes in Australia is poorly known. This is particularly the case in the south-west of Western Australia, where there have been no previous comprehensive studies of the parasites of 14 native species and nine or more exotic species of fish found in freshwater habitats. This study represents a survey of the parasites of freshwater fishes in the South West Coast Drainage Division and reports 44 putative species of parasites in 1429 individual fishes of 18 different species (12 native and six exotic) from 29 locations. Parasites were found in 327 (22.88%) fishes, and of the infected fishes, 200 (61.16%) were infected with only one species of parasite and 127 (38.84%) were infected with two or more species of parasites. For helminth and arthropod parasites, which were more comprehensively surveyed than protozoan and myxozoans, I found 37 species compared to 77 species found in a recent study of fishes from the East Coast Drainage Division. The present study demonstrated that parasitic infection was significantly more common in native fish species (mean prevalence of infection with any species of parasite = 0.36 ± 0.09) than in exotic fish species (0.01 ± 0.12). Parasites were found in all native fish species, but in only two exotic fish species that were examined. Parasite regional and component community diversity were estimated by species richness (the number of species, S) and by an index of taxonomic diversity (HT). Both parasite species richness and parasite taxonomic diversity were significantly greater in native fish species (mean S = 10.5 ± 2.3; mean HT = 1.19 ± 0.14) than in exotic fish species (mean S = 1.6 ± 3.3; mean HT = 0.27 ± 0.20). These relationships were consistent over all geographic locations that were sampled. The reduced parasite load of exotic species compared to native species has been previous reported across a wide range of taxa. It is thought to arise partly because founding populations of hosts have a low probability of harbouring the species’ total parasite fauna, and partly because parasites that infect introduced exotic species may not be able to maintain their life cycle in the new environment. It has been suggested that a reduced parasite load increases the competitive ability of exotic species compared to native species (the parasite release hypothesis) and this may partly explain the abundance and apparent competitive success of exotic over native species of freshwater fish in the South West Coast Drainage Division. For native species of fish, there were major differences among species in both prevalence of parasitic infection and parasite community diversity, but this variation was not related to fish size, whether the fish were primarily freshwater or primarily estuarine, or whether they were primarily demersal or pelagic. In this study, I report two new parasites in south western Australian waters. Both are copepod parasites; Lernaea cyprinacea and a new species of Dermoergasilus. The Dermoergasilus appears to be native to the south-west of Western Australia and has been described as Dermoergasilus westernensis. It differs from previously described species in the genus principally by the armature of the legs. This new species was found on the gills of freshwater cobbler, Tandanus bostocki and western minnow, Galaxias occidentalis in two different river systems. Lernaea cyprinacea is an introduced parasitic copepod found on the skin and gills of freshwater fishes in many areas of the world. The parasite has not previously been reported in Western Australia. We found infestations of L. cyprinacea on four native fish species (G. occidentalis; Edelia vittata; Bostockia porosa; T. bostocki) and three introduced fish species (Carassius auratus; Gambusia holbrooki; Phalloceros caudimaculatus) at two localities in the Canning River, in the south-west of Western Australia. The parasite has the potential to have serious pathogenic effects on native fish species, although it appears to be currently localised to a small section of the Canning River. Over all localities from which fishes were sampled in the present study, the proportion of native freshwater fishes with parasitic infections and the component community diversity of the parasite fauna of native fishes were both negatively related to habitat disturbance, in particular to a suite of factors (river regulation, loss of riparian vegetation, eutrophication and presence of exotic fish species) that indicate increased human usage of the river and surrounding environment. The reduced parasite load and diversity in native fishes from south-west rivers with greater human usage was due principally to the loss of a number of species of trematode, cestode and nematode endoparasites which use fishes as intermediate hosts. Other studies have also found that endoparasites with complex life cycles are most likely to be adversely affected by environmental changes, presumably because any environmental changes which impact on either free-living parasite stages or on any of the hosts in the complex train of parasite transmission will reduce parasite population size and may cause local extinction of the parasite species. The most heavily infected species of native freshwater fish in the South West Coast Drainage Division was T. bostocki with 96% of all individuals containing at least one species of parasite. As with most freshwater fishes of south-west Australia, T. bostocki is limited in its distribution to waterways with relatively low salinity. The degree of parasitism and histopathology of internal and external organs in T. bostocki from the Blackwood River was examined over a period of rapid, seasonal changes in water salinity. As salinity increased, the infracommunity richness and prevalence of ectoparasites on the skin of fishes decreased, while the infracommunity richness and prevalence of endoparasites increased. This was associated with a decrease in histopathological lesion scores in the skin and an increase in histopathological lesion scores in internal organs, particularly the intestine. I hypothesise that the seasonal spike in salinity had two contrasting effects on parasitic infections of T. bostocki. Firstly, it increased the mortality rate of parasites directly exposed to water, leading to a decrease in ectoparasitic infection and associated pathology. Secondly, it suppressed immune function in fish, leading to a decreased mortality rate of parasites not directly exposed to water and a more severe pathological response to endoparasitism.

Gli stili APA, Harvard, Vancouver, ISO e altri

12

Rodgers, Gwendolen Mary. "Colour, oddity and the social behaviour of freshwater fishes". Thesis, University of Leeds, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.579540.

Testo completo

Abstract (sommario):

This thesis investigates the interactions between some different elements of colour in group-living freshwater fishes, oddity in groups and the effects of these on observed behaviour. In the early chapters (2-4), I address the rapid colour change of which such fishes are capable. I investigate how social and habitat preferences interact with this morphological change, showing that physiological colour change can be as a direct result of changing habitat colour, and that the resulting body colour influcences social and habitat choice. I reveal a second function to this colour change, in dominance signalling, and discuss the social and other costs associated with physiological melanic colour change. The later chapters are focussed on some other aspects of oddity and risk in social behaviour of freshwater fishes. In chapter 5 I test a model predicting mixed phenotype grouping, concluding that prey animals must balance the relative risks of oddity and conspicuousness in their social decisions, potentially leading to the evolution of mixed phenotype grouping as a response to predation risk alone. Chapter 6 further investigates body size-oddity in the Trinidadian guppy, revealing body-size differences in social preferences. I elaborate on this finding in chapter 7 by discovering that large prey are at greater risk than small prey, given their oddity in a group, and that the differing social preferences are as a result of 'poor' decision makers being more easily captured and removed from the population by predators, leaving only 'good' decision makers to grow large .

Gli stili APA, Harvard, Vancouver, ISO e altri

13

Chakona, Albert. "Comparative biogeography and ecology of freshwater fishes in the Breede and associated river systems, South Africa". Thesis, Rhodes University, 2012. http://hdl.handle.net/10962/d1015694.

Testo completo

Abstract (sommario):

Distribution patterns and levels of genetic diversity in extant taxa are a product of complex palaeogeographic processes and climatic oscillations as well as the species’ intrinsic ecological adaptations. The Cape Floristic Region of South Africa presents a unique system for studying the processes that promote species diversification and distribution patterns. This region has a high degree of endemism of both terrestrial and aquatic biota and is clearly isolated from neighbouring areas by the Cape Fold Mountains and the Great Escarpment. The objective of this study was to firstly examine the ecology of freshwater fishes belonging to the genera Galaxias, Pseudobarbus and Sandelia in the south-western CFR. This was followed by an assessment of the genetic diversity of these taxa. Unique lineages were identified and their distribution was mapped. The work aimed to explore the role of the region’s complex palaeogeographic and climatic history as well as the role of the species’ ecological adaptations in driving lineage diversification and shaping contemporary distribution patterns. The four main components of the study can be summarised as follows: 1. Habitat associations of three widely distributed lineages of Galaxias zebratus Pseudobarbus burchelli and Sandelia capensis were evaluated at multiple localities in minimally disturbed mountain tributaries of the Breede, Duiwenhoks and Goukou River systems. The lineages have distinct habitat associations which were related to differences in their morphological traits. The slender-bodied Galaxias ‘nebula’ and the fusiform-shaped Pseudobarbus ‘Breede’ are capable of exploiting upper reaches with faster water velocity. By contrast, the laterally compressed Sandelia ‘eastern’ is restricted to lower reaches, making this lineage more susceptible to a wide array of impacts. 2. A recently discovered lineage of Galaxias zebratus, (Galaxias ‘nebula’), was found to be capable of tolerating emersion for a prolonged period of time. This is the first time that such capabilities have been documented in an African galaxiid. These adaptations have implications for the interpretation of Galaxias ‘nebula’s wide distribution range. 3. The phylogeography of Galaxias ‘nebula’ across its entire distribution range was investigated using two mitochondrial genes (cytochrome c oxidase subunit I (COI) and cytochrome b (cyt b)). This lineage has a complex evolutionary history that was influenced by both intrinsic and extrinsic factors. Rare events such as episodic drainage connections during Pleistocene and Holocene pluvial periods, possibly augmented by river confluences during periods of lower sea-levels and river capture events seem to be the most credible explanation for the extensive contemporary distribution and the relatively shallow genetic divergence between different river systems. 4. Mitochondrial cyt b sequences were used (i) to assess genetic diversity in G. zebratus, P. burchelli and S. capensis from the south-western CFR and (ii) to determine the roles of intrinsic ecological adaptations and extrinsic landscape and climatic changes in promoting genetic diversification and shaping present day distribution patterns of lineages in the three taxa. Marine incursions during periods of major sea-level transgressions are proposed to have isolated populations in upland refugia, thereby driving allopatric divergence in these species. Subsequent connections of rivers during wetter periods and lower sea-levels are proposed to have facilitated post-speciation dispersal of lineages to attain present day distribution patterns. While detailed morphological studies and further genetic analysis are needed to substantiate the taxonomic status of the newly discovered lineages of Galaxias zebratus, Pseudobarbus burchelli and Sandelia capensis, results of the present study indicate that the south-western CFR represents a previously unrecognised centre of freshwater fish diversity and microendemism in the broader Cape Floristic Region. Accurate identification of lineages and comprehensive mapping of their distribution is a fundamental pre-requisite for ecological studies, assessing conservation status and implementation of appropriate conservation measures.

Gli stili APA, Harvard, Vancouver, ISO e altri

14

Gardezi, Tariq. "Spatial scale and the ecological determinants of the distribution and diversity of fishes in Ontario lakes". Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=115911.

Testo completo

Abstract (sommario):

Data on the occurrence of freshwater fishes in Ontario lakes were used to evaluate the scale of the processes that are primarily responsible for shaping their distributions and patterns of diversity. In Chapter 2 it is shown that, regardless of the scale of analysis, the most important factors structuring their distributions are climatic measures of energy, suggesting that species tend to be able to survive heterogeneous conditions falling within large areas encompassing their climatic affinities. In Chapter 3 it is shown that the relationship between species richness and energy (annual potential evapotranspiration) changes according to the scale on which it is measured. The species-energy relationship is weak at the local scale and stronger and steeper at increasing regional scales. This scale dependence is due to the ability of high energy regions to accommodate relatively large numbers of rare or infrequent species, and reflects the regional scale at which species respond to environmental gradients, particularly those related to energy. In Chapter 4 the relationship between local and regional species richness is examined. It is found that mean richness of lakes is linearly related to the species richness of the watersheds in which they reside. Together, the results point to the importance of processes that are regional in scale for shaping species' distributions and patterns of diversity.

Gli stili APA, Harvard, Vancouver, ISO e altri

15

Smith, Scott A. 1978. "The importance of regional and historical processes in the assembly and maintenance of lower Mesoamerican freshwater fish communities /". Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=80875.

Testo completo

Abstract (sommario):

The relative importance of local, regional and historical processes to patterns of distribution and diversity of lower Mesoamerican (Panama and Costa Rica, LMA) freshwater fishes are examined at two different spatial scales. Biogeographic patterns of LMA freshwater fish communities at the spatial extent of LMA indicate that biological differences among species as well as regional and historical processes are quintessential to explaining the patters of turnover of community composition and species richness across the LMA Isthmus. The study of LMA freshwater fishes permits the inference that ecological interactions among species are not independent of a region's history, suggesting that regional and historical processes probably play an ongoing role in the maintenance of LMA freshwater fish communities. In addition, the study of the natural experiment of the Panama Canal provides a clear demonstration that dispersal, rather than local deterministic processes such as competition and predation, previously set the upper limit of the number of fish species coexisting in local communities. Comparisons of species inventories established prior to Canal construction with contemporary species lists demonstrates a large net increase in species richness of local communities, suggesting that the local communities of the Panama Canal watershed were not saturated.

Gli stili APA, Harvard, Vancouver, ISO e altri

16

Khachonpisitsak, Salinee. "Biodiversity assessment of freshwater fishes : Thailand as a case study". Thesis, University of St Andrews, 2012. http://hdl.handle.net/10023/3559.

Testo completo

Abstract (sommario):

A key challenge in biodiversity is: How many species are there on earth? This issue is especially acute in poorly surveyed regions with high diversity, particularly Southeast Asia that also experiences many limitations such as lack of funds, documents and experts. To help meet this challenge, I have developed a five-tiered approach for diversity measurement of freshwater fish for use in Thailand. This is: (1) the creation of a newly updated species inventory that uses existing data; (2) exploration of the patterns of species richness, endemism, and uniqueness; (3) estimation of the total species richness; (4) investigation of patterns of rarity; and (5) integration of this knowledge into conservation practice. The system should be applicable to other regions and other taxa where a similar challenge exists. My work shows that eight hundred and seventy-two species in 17 orders, 55 families and 255 genera of freshwater fishes, accounting for roughly 10% of the world's freshwater fish diversity, have been reported for Thailand to date. This number was derived from information in the museum collections, literature and all other available sources, including reports written in Thai as well as in English. During this work I uncovered many gaps in biodiversity information, in terms of taxonomic and spatial records, though some families and basins are better represented than others. Taxonomic uncertainty also continues to be a challenge for taxonomists and users. The high diversity of freshwater fishes in Thailand is the result of both high alpha (α) diversity (diversity within a particular locality) and beta (β) diversity (diversity differences between localities). I concluded that the substantial beta diversity I detected is associated with the geographical separation of the six river basins in Thailand. For example, the species composition of freshwater fishes in the Salween Basin dramatically differs from all other basins of Thailand. In contrast, the Chao Phraya Basin and the Mekong Basin contain the greatest number of shared species. Approximately 55% of species have a wide distribution range (being reported from more than two basins), whereas 45% are highly restricted within a single basin. Analyses using species richness estimators suggest that the figure of 872 species is an underestimate and that there may be between 1000 and 1300 fish species in Thailand, in other words an increase of between 14.7% and 49.1% over the list I compiled (which is itself an increase of 52.2% over the last report in 1997). Freshwater fish have become increasingly vulnerable to anthropogenic activities. Of the 872 Thai fish species, 6.8% and 15.1% are globally and nationally threatened, respectively. Nonetheless, a striking feature of the database is that the conservation status of the vast majority of species has not so far been assessed, either globally or nationally. Scientists and policy makers will find these results useful in appreciating the magnitude of the tasks involved in surveying, describing and conserving the country's freshwater fish biota. My work highlights localities and taxa where conservation is a priority and is thus an important resource for policy makers and conservation planners concerned with the management of freshwater fish in Thailand.

Gli stili APA, Harvard, Vancouver, ISO e altri

17

Phillip, Dawn Arlene Teresa. "Biodiversity of freshwater fishes of Trinidad and Tobago, West Indies". Thesis, University of St Andrews, 1998. http://hdl.handle.net/10023/2832.

Testo completo

Abstract (sommario):

The proximity of the speciose South American continent to Trinidad and Tobago ensures that these islands have a rich and dynamic fauna. According to the equilibrium theory of island biogeography (MacArthur & Wilson 1967), these islands should be subjected to frequent immigrations from the nearby continent, and these additions will, in response, fuel local extinctions to maintain a balance of species richness. The aquatic habitat is further impacted by man's activities, (Government of Trinidad and Tobago 1962; Government of Trinidad and Tobago 1976b) which have the potential to amplify the natural rates of immigration and extinction. Despite the possible consequences, the effects of this disturbance on the fish fauna have not been studied. A survey of the islands' freshwater fishes was therefore carried out to investigate the natural spatial and temporal dynamics of local fish communities, and the effects of anthropogenic perturbations, on these. These baseline data can be used as a benchmark to address some of the problems that are threatening the fish diversity of Trinidad and Tobago. The fish fauna of Trinidad and Tobago is diverse. Total species richness was estimated at between 37 and 40. Four zoogeographic zones were recognised. A zone of Antillean fishes included Tobago and the north coast of Trinidad. A zone of recent colonising South American fauna existed along the south coast of Trinidad. The rest of Trinidad contained a relict South American fauna dating back to the time when Trinidad was still part of the mainland. Included here was a centrally located zone of unstable fauna at risk of local extinction. The fish fauna was temporally dynamic due to frequent colonisation and extinction events. Examination of the historic record showed that observed species richness varied from 38 to 43 between the mid 1950s and the present. During this time there were 15 introductions and 12 local extinctions. A conservative estimate was that a new species was recorded for Trinidad almost every three years. The geographic distribution of species also showed temporal changes which indicated a natural tendency of the fauna to vary over time. Human interference, particularly the introduction of exotic fish species and long-term habitat alteration, has affected species diversity. Forty seven percent of the new introductions and 43% of the extinctions were human-introduced exotics. About four fifths of sites in Trinidad, and almost one fifth of the sites in Tobago, were either perturbed or polluted. Polluted rivers coincided with areas of high urbanisation and industrial development in the west and southwest of Trinidad. Several effects of human interference on the fauna were recorded. Almost 8% of the sites examined contained one of the three exotic species still extant on the island. At each of these sites, the exotic species accounted for between 1.3% and 80.4%, by number, of the fish caught. Some of the effects of habitat disturbance on individual sites were increased frequency of diseases, extirpation of species, changes in species richness and other diversity measures, and the eventual regression of the fish community to opportunistic species (r-strategists). The potential of two fishes, Poecilia reticulata and Astyanax bimaculatus, as indicator species was examined. Astyanax showed better potential as an indicator of habitat quality as it was not found in depauperate communities, typical of severely disturbed habitats, and its proportional abundance and biomass were negatively affected by pollution. Poecilia populations, on the other hand, were found to be insensitive to habitat quality when the above-mentioned criteria were used. They did, however, have a high frequency of diseased individuals at polluted sites. One of the aims of conservation is to protect that portion of biodiversity most at risk of extinction, the rare species (Rabinowitz 1986). Over 70% of freshwater fish species found in Trinidad and Tobago were classified as rare in these islands. This fact, in addition to the loss of diversity recorded for some sites indicates that the implementation of a management strategy for the conservation of the freshwater fish fauna of Trinidad and Tobago is imperative. The management strategy should focus on the amelioration and protection of aquatic habitats since at least 80% of the rare species had either a restricted geographic distribution or narrow habitat specificity. Additionally, protection from overexploitation should be offered to commercially important species with only small populations. Finally, a minimum sample size of 35 sites, spread over different zoogeographic areas, is recommended for estimating species richness for monitoring, an intrinsic part of any management strategy.

Gli stili APA, Harvard, Vancouver, ISO e altri

18

Aldridge, Brenda Michelle Te Aroha. "Restoring giant kokopu (Galaxias argenteus) populations in Hamilton's urban streams". The University of Waikato, 2008. http://hdl.handle.net/10289/2516.

Testo completo

Abstract (sommario):

In this study, options for restoring fish populations in Hamilton City (37.47'S, 175.19'E) were explored. Habitat and fish populations in Hamilton urban streams were manipulated using a two-fold experimental design. Firstly, habitat was enhanced in ten urban streams with three continuous treatments in a 60-m reach at each site (20 m with 10 ponga logs, 20 m with 20 hollow clay pipes, and 20 m with no added structure). Secondly, juvenile farm-reared giant kokopu (Galaxias argenteus), were stocked into five of the enhanced stream sections. Giant kokopu are threatened and occur naturally in Hamilton urban streams in sparse populations. The abundance of wild fish was monitored before and after enhancement and fish release from November 2006 to November 2007. Stocked fish were monitored for eight months, from April to November 2007. Over this time electric fishing was conducted three times, trap nets (Gee minnow and fyke nets) were set monthly and spotlighting was conducted monthly at three release sites where water clarity allowed. Anticipated outcomes of this research were; to determine whether giant kokopu abundance in Hamilton urban streams is limited by recruitment or by habitat, and to assist with the development of methods to restore fish populations in Hamilton City urban streams. Logs used as enhancement structures in Hamilton urban streams provided more stable habitat for fish and created more suitable microhabitat than pipe structures. Pipes moved considerably during high flows, and their instability made them less effective at providing habitat. Within the study sites there appeared to be complex interactions with turbidity, stream width and depth, which complicated the effect of the habitat structures. The limited replication and variability among sites contributed to statistically insignificant results using analysis of variance. Retention and recapture rates of stocked juvenile giant kokopu were greatest at Site M11, where the stream was narrow, shallow, clear and had lower numbers and biomass of shortfin eels, compared to other survey sites. Marked and released giant kokopu were retained in the release reaches at four of the five sites, for a minimum of four months, and exhibited substantial growth. Daily growth of juvenile giant kokopu ranged from 0.19 to 0.33 mm day-1 and from 0.03 to 0.11 g day-1, exhibiting substantial growth over winter. Giant kokopu appeared to have a slight bias to the log section of enhanced habitat, but habitat selection appeared to be overwhelmingly controlled by initial habitat selection. The stocking of farm-reared fish into urban streams was largely successful, but the success of the habitat enhancement was variable and further work is required to determine better techniques for habitat enhancement in these urban environments. It is concluded that releasing farm-reared giant kokopu can be used to restore populations especially where recruitment limitations control fish abundance and diversity.

Gli stili APA, Harvard, Vancouver, ISO e altri

19

Mpherwane, Salome Kedibone. "An investigation into the allozyme genetic variation patterns among populations of freshwater fish from different river systems of Southern Africa". Thesis, University of Limpopo (Turfloop Campus), 2011. http://hdl.handle.net/10386/910.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

20

Traas, Graham Ronald Louis. "The conservation and management of freshwater fishes in the Greater Addo Elephant National Park". Thesis, Rhodes University, 2009. http://eprints.ru.ac.za/1687/.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

21

Deweber, Jefferson Tyrell. "Background studies on the fishes of the Opossum Creek / Camp Hydaway Lake system and effects of an herbicide on the lake's aquatic plants /". Lynchburg, VA : Liberty University, 2007. http://digitalcommons.liberty.edu.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

22

Lee, Ching-man. "Epidemiology of laribacter hongkongensis in freshwater fish /". View the Table of Contents & Abstract, 2005. http://sunzi.lib.hku.hk/hkuto/record/B3149447X.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

23

Medeiros, Elvio S. F. "Trophic ecology and energy sources for fish on the floodplain of a regulated dryland river Macintyre River, Australia /". Connect to this title online, 2004. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20051115.174552/.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

24

Reeves, Richard Guy. "Molecular zoogeography and evolution of primary freshwater fishes in Central-America". Thesis, University of Newcastle Upon Tyne, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340798.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

25

Ahmad, Amirrudin Bin. "Biological diversity of freshwater fishes in small streams in peninsular Malaysia". Thesis, University of St Andrews, 2012. http://hdl.handle.net/10023/3144.

Testo completo

Abstract (sommario):

Peninsular Malaysia has a diverse flora and fauna, much of which is yet to be documented. The freshwater fishes are one important group that have received little attention. Accordingly, the overarching goal of my study is to investigate the pattern of species richness and analyse the community composition and assemblage structure of fishes in the small streams in Peninsular Malaysia. Small stream habitats appeared to be particularly important repositories of fish biodiversity in this region thus obtaining a reliable census of species occurring in such habitats is critical for conservation and management of biodiversity. Although samplings were far from completed, these habitats support a great variety of species with more than 100 species were recorded from fifty streams sampled in this study. A few are extremely rare with restricted distribution and can thus be considered important in biodiversity conservation of the Peninsular Malaysian ichthyofauna. Human-influenced modification of lowland, headwater stream habitats in Peninsular Malaysia is common and often exemplified by the creation of pools in stretches of rapids and riffles. However, it was not possible to separate pristine and disturbed sites which contained almost identical for species diversity. These findings suggest that local habitat modification does not necessarily cause a decrease in freshwater fish diversity, with only minor negative consequences for other community variables recorded in this study, and therefore raise interesting issues regarding conservation. That said it remains premature to conclude that small stream fishes are insensitive to disturbance and thus their potential utility as bioindicators of disturbance-influenced community changes remain to be confirmed. The maintenance practises being applied to small streams modified for recreational usage were not imposing detectable negative consequences, at least across the sites sampled in this study. The rich diversity of tropical stream environments is the result of both within-habitat (alpha) diversity and between-habitat (beta) diversity. The results showed that there was substantial beta diversity particularly amongst sites that are geographically separated from one another. On the contrary, the lowest beta diversity values were portrayed by contiguous sites. Many fishes exhibited discontinuous patterns of distribution and were considered to be rare while only a handful were widely distributed and abundant. Ordination based on the relative resemblance of fish communities to one another support the existence of two distinct ichthyogeographic divisions in Peninsular Malaysia. It was possible to assign the species recorded to all seven of Rabinowitz's categories of rarity, with at least 10 restricted to a single stream and locally scarce, although not all of these could be described as hyper-endemic. It is recommended that a sizeable augmentation of the existing protected areas is needed to safeguard Malaysia's exceptionally diverse stream-dwelling fauna of which fishes are simply the most well-known inhabitants. Conservation managers should therefore place particular emphasis on small streams since localities in close proximity to one another can exhibit surprisingly high beta diversity, meaning that partial or small-scale habitat protection may prove insufficient.

Gli stili APA, Harvard, Vancouver, ISO e altri

26

Scott, Lucy Elizabeth Powell. "The development of a geographic information systems based atlas of southern African freshwater fish, and its application to biogeographic analysis". Thesis, Rhodes University, 2000. http://hdl.handle.net/10962/d1005099.

Testo completo

Abstract (sommario):

A Geographic Information Systems (GIS) atlas of southern African freshwater fish was developed for the SADC countries from natural history collection specimens, hydrological, topographical and climatological data. The primary purpose of the development of the atlas of freshwater fish was the construction of a practical framework to transform vast amounts of existing biological data for use in research and management of aquatic resources. The database of freshwater fish collection specimens that was incorporated into the atlas, was developed in association with ALCOM (Aquatic Resources Management for Local Community Development Programme). The development of advanced computing and GIS technology has increased the scope of biological atlas projects by facilitating the integration of large amounts of spatial data to produce derived databases for specific applications. The atlas of freshwater fish was constructed using TNTmips GIS software as the most practical system available for managing and analysing biological data with a spatial component. The atlas contains 35 180 comprehensive distribution records of 735 species of fish. It has many applications as an inventory of ichthyofaunal spatial biodiversity, including those of conservation planning, environmental assessment and biogeographic research. Biogeographic studies have traditionally been subjective due to the logistical problems of working with large amounts of distribution data, although some small-scale quantitative research has been carried out in the past. The content of the atlas of freshwater fish is tested with respect to these previous studies, on known patterns of freshwater fish distributions, and the analytical capability of the atlas is tested and demonstrated with some new preliminary approaches to the analysis of freshwater fish distributions in southern Africa.

Gli stili APA, Harvard, Vancouver, ISO e altri

27

Currie, Rebecca J. (Rebecca Jean). "Upper and Lower Temperature Tolerances of Three Freshwater Game-Fish Species Exposed to Cycling Temperatures". Thesis, University of North Texas, 1995. https://digital.library.unt.edu/ark:/67531/metadc279105/.

Testo completo

Abstract (sommario):

A total of 670 critical thermal maxima (CTMax) and minima (CTMin) were determined for three freshwater fishes acclimated to three constant temperatures and a diel regimen cycling between the lowest and highest acclimation temperatures. In all species temperature tolerance was directly related to acclimation temperature and slopes relating these variables indicate that acclimation temperature has a greater influence on tolerance of low rather than high temperatures. CTMax and CTMin values generated following exposure to 32 days of oscillating temperatures indicate that in general, fishes had temperature tolerance acclimation states consistent with the average temperature and not either the highest or lowest temperature of the diel cycle.

Gli stili APA, Harvard, Vancouver, ISO e altri

28

Holzer, Astrid Sibylle. "Molecular studies on Sphaerospora truttae and other freshwater myxozoans". Thesis, University of Stirling, 2001. http://hdl.handle.net/1893/21826.

Testo completo

Abstract (sommario):

This study investigates the life cycle of Sphaerospora truttae, a myxozoan parasite of the Atlantic salmon, using molecular methods based on the 185 rONA. DNA sequencing showed that the 185 rONA of S. truttae differs substantially from the sequence obtained from its proposed alternate actinosporean life cycle stage, Echinactinomyxon type 5. With more than 90% sequence identity Echinactinomyxon type 5 is closely related to Myxobolus portucalensis whereas S. truttae with an extraordinary long 185 sequence (2541 bp), with inserts in the variable regions of the gene, does not relate closely to any myxozoans. On the basis of the obtained sequence for S. truttae, a single round nested peR assay was developed which allows low-level detection and specific identification of S. truttae in all life cycle stages. Furthermore, two of the primers from the peR assay were successfully used on tissue sections in an optimised in situ hybridisation (ISH) protocol. ISH experimentally identified the gills as the predominant entry locus of S. trottse into the fish host and it detected the spatiotemporal migration of the parasite via the vascular system into the target organ, the kidney. The ISH protocol and the peR assay were also used to screen oligochaetes and other co-occurring invertebrates for S. truttae infection but an alternate host for S. truttse could not be identified. However, 12 actinosporean stages were found and they were characterized on the basis of their 185 rONA, together with 9 further myxosporean species from wild fish in the same riverine habitat. Three actinosporeans were found to be genetically identical with three myxosporeans (Myxidium truttae, Chloromyxum truttse and Chloromyxum sp.) and thus represent alternate life cycle stages of these species. Phlyogenetic analysis of the myxozoans identified a very basal position of S. truttae and S. elegans, as a sister group to the marine species. All other species were nested in the freshwater clades and clustered according to host tissue localization, but independent from host species or myxozoan spore taxonomy.

Gli stili APA, Harvard, Vancouver, ISO e altri

29

Carrier, Roxie. "Temperature Tolerance of Freshwater Fish Exposed to Water-Borne Cadmium". Thesis, North Texas State University, 1987. https://digital.library.unt.edu/ark:/67531/metadc504077/.

Testo completo

Abstract (sommario):

Lethal toxicity values (96 h LC50; mg Cd/L) for the test species were similar: Lepomis cyanellus, 11.52; Notropis lutrensis, 6.62; Pimephales promelus, 3.58. However the effects of cadmium concentration and exposure time on temperature tolerance varied between species. Neither cadmium concentration nor exposure time had a significant effect on the CTM of green sunfish. Both cadmium concentration and exposure time had a significant effect on the CTMs of red shiners and fathead minnows. By day 10 mean CTMs were 2.3 t- 4.5 C (red shiners) and 4.2 to 5.7 C (fathead minnows) lower than control CTM. These results suggest a potential problem in cadmium contaminated systems for high environmental temperatures to stress or kill fish.

Gli stili APA, Harvard, Vancouver, ISO e altri

30

Roni, Philip. "Responses of fishes and salamanders to instream restoration efforts in western Oregon and Washington /". Thesis, Connect to this title online; UW restricted, 2000. http://hdl.handle.net/1773/5383.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

31

Williams, Chris F. "Impact assessment of non-native parasites in freshwater fisheries in England and Wales". Thesis, University of Stirling, 2007. http://hdl.handle.net/1893/410.

Testo completo

Abstract (sommario):

Non-native parasites pose a significant threat to aquatic bio-diversity and fishery development. Many factors have facilitated the introduction of non-native parasites into England and Wales. Identifying the effects of these parasites and the importance of any changes to wild fish populations represents a considerable challenge. However, in order for the Environment Agency to identify future disease threats, effectively manage resources and implement practical and sustainable control measures, the risks posed by these parasites to fisheries must be better understood. A structured, risk-assessment process for non-native freshwater parasites is proposed. This approach includes procedures for hazard identification, impact assessment, risk management and communication. A quantitative approach to hazard identification provides an initial prediction of impact at the time of introduction to inform decisionmaking and guide preliminary control measures. This is followed by a more comprehensive framework for impact assessment that promotes understanding of changes at host, population and fishery levels. These are placed into context with the economic and ecological value of native resources. An independent 'non-native parasite review group' has been convened to ensure consistency of policy decisions and clear communication of disease risks to interested bodies. It is hoped that this wil assist the management of future invasions and provide a scientifically robust foundation on which to base proportionate control measures. The Category 2 parasites are defined as "species having a significant disease potential when introduced into waters where they do not already exist, or are non-indigenous species with unknown pathogenicity and distribution". Understanding of the dangers posed by these parasites varies considerably. Ergasilus sieboldi, Anguilicola crassus, Bothriocephalus acheilognathi and Lernaea cyprinacea, are well recognised non-native fish pathogens that pose a considerable threat to fisheries. Conversely, the effects of other introduced parasites remain poorly understood. In many cases, a paucity of published literature at the time of introduction has limited a reliable assessment of impact. Four non-native parasites were considered a priority for further study. These were Paraergasilus longidigitus (Copepoda: Poecilostomatoida), Ergasilus briani (Copepoda: Caryophylldae) Poecilostomatoida ), Atractolytocestus huronensis (Cestoda: and Philometroides sanguinea (Nematoda: Philometridae). Pathological, epidemiological and experimental investigations were undertaken to assess the effects of these parasites at host and population levels. P. longidigitus can cause pronounced pathological changes to the olfactory epithelium of infected fish. Although this damage provides the potential for disruption to spawning through reduced sensitivity to reproductive chemical cues, experimental observations combined with seasonality studies suggest that the parasite is unlikely to disrupt reproduction within infected cyprinid fisheries. Similarly, studies conducted on the caryophylidean cestode A. huronensis provide little evidence to suggest that the parasites poses a threat to car fisheries. Damage within the intesinal tract was characterised by relatively mild mechanical and inflammatory changes. Infections of up 213 parasites had no adverse affect upon the conditon of common carp. Based on these findings and the application of the aformentioned risk model, P. longidigitus and A. huronensis are considered to be of low disease risk to fisheries. The pathology of E. briani and P. sanguinea are described for the first time. Literature suggests that both parasites are pathogenic to juvenile fIsh. E. briani causes a number of pathological changes within the gils of juvenile cyprinids, although these remain localised due to the very strict site specificity of the parasite. Migrations of the nematode P. sanguinea causes damage to the fins and caudal musculature of juvenile crucian car. For both parasites, the extent and severity of pathological changes are inversely proprtional to host size. Further studies at the population level are needed before an assessment of impact to fisheries can be made. The difficulties associated with studying the effects of introduced parasites to juvenile fish populations in the wild are recognised. Recommendations for further study are given.

Gli stili APA, Harvard, Vancouver, ISO e altri

32

Deweber, Jefferson T. "An introductory look at the fishes of the Opossum Creek / Camp Hydaway Lake System and the effects of an herbicide on the Lake's aquatic plants". Lynchburg, Va. : Liberty University, 2007. http://digitalcommons.liberty.edu.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

33

Anandan, Chantelle. "Morphological and genetic differentiation of the fish eye fluke Diplostomum spp. (Digenea, Diplostomatidae)". Thesis, University of Aberdeen, 2004. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=186183.

Testo completo

Abstract (sommario):

Digenean eye-flukes of the genus Diplostomum (Family: Diplostomatidae) are common in the eyes of freshwater fishes. Diplostomum spp. infections can lead to severe detrimental deformities and even death to both farmed and wild fish species. Identification of Diplostomum spp. in the fish host (metacercaria) is challenging because species are morphologically indistinguishable. Since Diplostomum spp. are difficult to identify the literature is confounded by synonymy and as a result, the taxonomic status of the genus remains unclear. Thus, it is difficult to ascertain the pathological status, diversity and geographical distribution of this economically important group of parasites. The purpose of this study was to define operational taxonomic units (OTU) using morphometric and molecular data collected from Diplostomum spp. metacercaria in the U.K. Data was collected from ten fish species and four host locations: lens humor retina and brain. Four OTU were defined by host location using morphometric analysis. Hence the morphometric analysis proved metacercaria from the four host locations were different in size and shape. Four OTU were discriminated using PCR-RFLP and sequence analysis. However, with the exception of brain parasites, those in the fish eye (lens, humor and retina) could not be differentiated by host location. Therefore, although parasites in the three fish eye locations were different in size and shape, they were not genetically different. The OTU ITS1 sequence data was compared to published Diplostomum spp. sequences and the following genetic similarity was revealed: OTU1 showed 99.4% similarity to D. mergi; OTU2 99.7% similarity to D. baeri and OTU3 99.7% similarity to D. paracaudum/D. spathaceum. OTU4 in the fish brain has previously been described as D. phoxini. The molecular approach was subsequently used in a temporal study to assess Diplostomum spp. metacercaria infections over the course of a year in a rainbow trout farm.

Gli stili APA, Harvard, Vancouver, ISO e altri

34

Bleackley, Natalie Anne. "Biology of common bully (Gobiomorphus cotidianus)". The University of Waikato, 2008. http://adt.waikato.ac.nz/public/adt-uow20080320.150044/index.html.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

35

Rashash, Diana M. C. "Identification and characterization of odorous metabolites produced by selected freshwater algae". Diss., This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-06062008-164628/.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

36

Bannon, Henry James. "Effects of Water Quality Parameters on Prolonged Swimming Ability of Freshwater Fishes". The University of Waikato, 2006. http://hdl.handle.net/10289/2618.

Testo completo

Abstract (sommario):

The critical swimming speed (Ucrit) of rainbow trout parr (Oncorhynchus mykiss) and three life stages of Galaxias maculatus, larval (whitebait), postlarval inanga and adult inanga, were tested at temperatures from 5oC to 25oC. All fish were swum at their acclimation temperature under normoxic conditions to determine the optimal aerobic exercise temperature. To determine whether acclimation affected swimming ability, trout parr acclimated to either 10oC or 20oC were swum at 20oC and 10oC, respectively. The potential effect of mild hypoxia (75% saturation) on trout parr and whitebait was also examined at 10oC, 15oC and 20oC, and also tested separately and in combination were the effects of mild hypoxia and severe anaemia on the prolonged swimming ability of trout smolts at temperatures from 10oC to 20oC. For all trout experiments, blood samples were taken from non-exercised and exercised fish by acute caudal venepuncture to determine haematological responses to both acclimation and exercise. Under normoxic conditions, Ucrit max for trout parr (7.0 0.5 cm fork length) was calculated to be 5.8 body lengths per second (BL s-1) at 15.1oC, but declined at lower and higher temperatures. This result implies that swimming performance was limited by temperature below 15oC, whereas performance at higher temperatures was limited by oxygen availability. In support of this hypothesis, mild hypoxia (75% saturation) had no effect at 10oC or 15oC but caused a significant reduction in Ucrit at 20oC. However, fish acclimated at 20oC showed an adaptive elevation in oxygen carrying capacity due to an increase in mean erythrocyte volume and haemoglobin content. Furthermore, acclimation to 20oC improved warm water swimming performance. Trout parr acclimated to 10oC performed significantly worse than fish acclimated to 20oC when swum at 20oC. However, trout parr acclimated to 20oC performed as well as fish acclimated to 10oC when swum at 10oC. Following exercise, haematocrit was elevated under both normoxic and hypoxic conditions. However, the primary cause of this apparent increase in oxygen carrying capacity was splenic release of erythrocytes under normoxic conditions, whereas stress-induced erythrocytic swelling contributed to the observed increase in hypoxia. This contrasting response was most pronounced at 10oC. Larval whitebait (4.7 - 5.0 cm total length (TL)) also showed a temperature dependence of prolonged swimming ability with Ucrit max calculated to be 5.1 BL s-1 at 17.7oC. Hypoxia significantly reduced Ucrit at 15oC and 20oC, lowering the optimal aerobic temperature to 13.9oC and reducing Ucrit to 4.2 BL s-1. Mild hypoxia therefore had a more pronounced impact on inanga whitebait than trout. Postlarval inanga (3.9 - 4.0 cm TL) performed poorly at higher temperatures with Ucrit max of 5.6 BL s-1 at 9.4oC indicating an ontogenetic change in swimming ability, possibly resulting from a developmental shift in red muscle kinetics or a greater dependence on anaerobic muscle. Adult inanga (5.5 - 6.8 cm TL) prolonged swimming ability showed similar temperature dependence to that of inanga whitebait but lower relative swimming speeds due to their larger size. The dramatic decline in performance exhibited by juveniles at warmer temperatures was not apparent in adults. Ucrit max for adults was 4.0 BL s-1 at 18.3oC. The critical swimming speed of trout smolts, subjected to mild hypoxia (6.8 mg

Gli stili APA, Harvard, Vancouver, ISO e altri

37

Barber, Iain. "Effects of helminth infections on the shoaling behaviour of small freshwater fishes". Thesis, University of Glasgow, 1995. http://theses.gla.ac.uk/6572/.

Testo completo

Abstract (sommario):

The findings of laboratory and field investigations into various aspects of the effects of helminth parasites on the ecology and behaviour of minnows Phoxinus phoxinus and three spined sticklebacks Gazsterosteus aculeatus are reported. A sampling programme was implemented at Loch Maragan over a 16 month period between October 1992 and January 1994 (Chapter 2). The overall prevalence of L intestinalis in minnows from the loch was 17.8%: plerocercoids were found to be weakly overdispersed within the minnow population, although one plerocercoid generally dominated multiple infections whenever they occurred. Both total parasite weight, and the weight of the largest plerocercoid present in an infection were found to be positively and highly significantly correlated with host length, with older, larger fish exhibiting higher parasite burdens. This suggests that fish become infected with L. intestinalis at Loch Maragan during a temporally-limited period during early life. No significant effect of the parasite on host body condition was detected. A qualitative model for transmission of L. intestinalis at the site, based on the available epidemiological data and the prevailing ecological conditions, is proposed. The shoaling and investigative behaviours of minnows from two sites in central Scotland were found to differ, and possible reasons for this variation, based on the ecological disparity between the two sites are suggested (Chapter 3). Both small and medium-sized fish formed more cohesive shoals and schooled more frequently when water depth was reduced, but small fish polarised more frequently than medium-sized fish for any given water depth. The effects of visual oddity on individual shoaling behaviour were investigated (Chapter 3). Size-oddity had little influence on shoaling behaviour in the experimental trials, since the non-uniformity of individual small minnows, when placed in a tank with a group of medium-sized minnows, did not affect their shoaling tendency.

Gli stili APA, Harvard, Vancouver, ISO e altri

38

Yamane, Hideyuki. "Reproductive strategies and interspecific interactions in nest-association systems of freshwater fishes". 京都大学 (Kyoto University), 2011. http://hdl.handle.net/2433/142416.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

39

Liang, Yan. "Reclamation of wastewater for polyculture of freshwater fish". HKBU Institutional Repository, 1997. http://repository.hkbu.edu.hk/etd_ra/137.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

40

Taylor, Lisa N. McDonald D. G. "Physiological indicators of waterborne copper toxicity in freshwater fish /". *McMaster only, 2002.

Cerca il testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

41

Lee, Ching-man, e 李靜敏. "Epidemiology of laribacter hongkongensis in freshwater fish". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2005. http://hub.hku.hk/bib/B45010213.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

42

Hansen, Jonathan Ford. "Long-term implications of dam removal for mesohabitat and macroinvertebrate communities in Michigan and Wisconsin rivers". Diss., Connect to online resource - MSU authorized users, 2008.

Cerca il testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

43

Rathete, Sello Athlone. "A comparative study on the effects of stress on some aspects of in vitro blood coagulation in two freshwater fish species". Thesis, University of Limpopo, 1993. http://hdl.handle.net/10386/2092.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

44

Pritt, Jeremy Joseph. "Defining rarity and determining the mechanisms of rarity for North American freshwater fishes". Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/31696.

Testo completo

Abstract (sommario):

Conserving rare species and protecting biodiversity depends on sound information on the nature of rarity. Rarity is multidimensional, presenting the need for a quantitative classification scheme by which to label species as rare or common. I defined rarity for freshwater fishes based on the range extents, habitat breadths, and site abundance and examined the relationship between these dimensions of rarity and imperilment. Imperiled fishes were most often rare by all three dimensions, whereas undesignated species were most often common by all three dimensions. Next, I examined the effect of sampling intensity on observed rarity of stream fish using different numerical and proportional rarity criteria and found that increasing sampling intensity increased the number of species labelled as rare with proportional criteria but did not affect the number of species labelled as rare with numerical criteria. Additional electrofishing passes within a fixed reach increases the likelihood of detecting rare and endemic species. A tradeoff between information collected and sampling resources should be carefully considered in the context of objectives when sampling for rare species. Finally, I examined the effect of regional and watershed habitat variables, biotic interaction variables, and instream habitat variables, on the rare or common status on 23 North American freshwater fishes. I also compared biological and reproductive traits among species classified into the rarity framework. Rarity was successfully explained in 19 of the 23 species and I found that regional and watershed habitat variables were the most important predictors of rarity. I also found that species large body size, high fecundity, and long age at maturity were generally more common by range extent and site abundance while those species that did not guard nests were more frequently rare by site abundance. These results indicate that large-scale variables can be used to successfully predict species rarity and rare fishes differ in their biology and reproduction from common fishes.
Master of Science

Gli stili APA, Harvard, Vancouver, ISO e altri

45

Hopkins, Rob. "Distributional Modeling Of Rare Fishes And Mussels: From Ecological Theory To Biodiversity Conservation". OpenSIUC, 2009. https://opensiuc.lib.siu.edu/dissertations/4.

Testo completo

Abstract (sommario):

Freshwater ecosystems are among the most threatened ecosystems on the planet. In recent years there has been increasing concerns over precipitous declines in population sizes and increasing rates of extinction of native freshwater fauna across North America. Nearly 50% of the mussel species and 25% of the fish species in North America are imperiled. Stream habitat degradation has been cited as the principal cause for declines, with anthropogenic land uses being the leading causes of stream degradation. Species distribution models (SDMs) have become an integral tool in ecological research and conservation planning. SDMs are reliant upon occurrence datasets for the taxa of concern and museum-based information has become a popular source for such data. In the first stage of my research, I developed a centralized database for Kentucky fishes based on museum-based information. Over the course of three years, the SIUC Ichthyology Lab built an occurrence dataset of Kentucky fishes consisting of more than 50,000 records dating back to the 1890s. Each record contains three pieces of information (1) species identification, (2) georeferenced locality, and (3) date of collection. In the second stage of my research, I investigated the use of multiscale landscape data in aquatic species distribution models using a case study of a freshwater mussel. The distribution of Rabbitsfoot (Quadrula cylindrica) in the upper Green River system (Ohio River drainage) was modeled with environmental variables from multiple spatial scales. Four types of landscape environment metrics were used, including: land use/land cover (LULC) pattern, LULC composition, soil composition, and geology composition. The study showed that LULC pattern metrics are very useful in modeling the distribution of Rabbitsfoot. Together with LULC compositional metrics, pattern metrics permitted a more detailed analysis of functional linkages between aquatic species distributions and landscape structure. Moreover, the inclusion of multiple spatial scales was necessary to accurately model the hierarchical processes in stream systems. Geomorphic features played an important role in regulating species distributions at intermediate and large scales while LULC variables appeared more influential at proximal scales. I then further tested the landscape-level approach to aquatic species distribution modeling using a case study of six narrow-range endemic fishes with contrasting biogeographies. Species biogeography did not appear to affect predictive performance and all models performed well statistically. Predictive maps showed accurate estimations of ranges for five of six species based on historical collections. The relative influence of each type of environmental feature and spatial scale varied markedly with between species. A hierarchical effect was detected for narrowly distributed species which were highly influenced by soil composition at larger spatial scales and land use/land cover (LULC) patterns at more proximal scales. Conversely, LULC pattern was the most influential feature for widely distributed at all spatial scales. Lastly, I developed a hierarchical approach to the selection and management of freshwater protected areas in the upper Green River system. By aligning the spatial scales and environmental variables analyzed at each stage in the conservation planning process, from species distribution modeling to reserve selection, I present a more robust methodology to conservation planning compared to traditional approaches. Using models of species richness fitted to landscape attributes, I also provided suggestions for landscape management strategies for each conservation unit. My research comprises the core conservation plan for the focal species in the upper Green River system.

Gli stili APA, Harvard, Vancouver, ISO e altri

46

Warnick, William A. "Sport fish consumption advisory for West Virginia". Morgantown, W. Va. : [West Virginia University Libraries], 2002. http://etd.wvu.edu/templates/showETD.cfm?recnum=2681.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

47

French, Kenneth J. "Mercury evolution in freshwater fish from reservoirs in Newfoundland, Canada". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq25841.pdf.

Testo completo

Gli stili APA, Harvard, Vancouver, ISO e altri

48

McGlashan, Dugald James, e piscador@hotmail com. "Consequences of Dispersal, Stream Structure and Earth History on Patterns of Allozyme and Mitochondrial DNA Variation of Three Species of Australian Freshwater Fish". Griffith University. Australian School of Environmental Studies, 2000. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20030226.152217.

Testo completo

Abstract (sommario):

Freshwater systems offer important opportunities to investigate the consequences of intrinsic biological and extrinsic environmental factors on the distribution of genetic variation, and hence population genetic structure. Drainages serve to isolate populations and so preserve historical imprints of population processes. Nevertheless, dispersal between and within drainages is important if the biology of the species confers a good dispersal capability. Knowledge of the population genetic structure or phylogeographic patterns of Australia's freshwater fish fauna is generally depauperate, and the present study aimed to increase this knowledge by investigating patterns of genetic diversity in three Australian species of freshwater fish. I was interested in the relative importance of dispersal capability, the hierarchical nature of stream structure and the consequences of earth history events on patterns of genetic diversity among populations. I examined three species from three families of Australian freshwater fish, Pseudomugil signifer (Pseudomugilidae), Craterocephalus stercusmuscarum (Atherinidae) and Hypseleotris compressa (Gobiidae). These species are abundant, have wide overlapping distributions and qualitatively different dispersal capabilities. I was interested in attempting to unravel how the biological, environmental and historical factors had served to influence the patterns and extent of genetic diversity within each species, thereby inferring some of the important evolutionary processes which have affected Australia's freshwater fauna. I used allozyme and 500-650bp sequences from the ATPase6 mitochondrial DNA (mtDNA) gene to quantify the patterns of genetic variation at several hierarchical levels: within populations, among populations within drainages and among drainages. I collected fish at several spatial scales, from species wide to multiple samples within drainages; samples were collected from the Northern Territory, Queensland and New South Wales. The species with the highest potential for dispersal, H. compressa, exhibited the lowest levels of genetic differentiation as measured at several allozyme loci (H. compressa: FST=0.014; P. signifer FST=0.58; C. stercusmuscarum FST=0.74). Populations of H. compressa also had low levels of mtDNA differentiation, with many recently derived haplotypes which were widespread along the coast of Queensland. This suggested either considerable gene flow occurs or recent demographic change in the populations sampled. As there was no relationship between geographic distance and genetic differentiation, the populations appeared to be out of genetic drift - gene flow equilibrium, assuming the two-dimensional stepping stone model of gene flow. Estimating contemporary gene flow was thus difficult. It was apparent that there has been a recent population expansion and / or contraction of H. compressa populations. It was concluded that there has been considerably more connectivity among populations of H. compressa in the recent past than either of the other study species. Populations of P. signifer showed considerable genetic subdivision at different hierarchical levels throughout the sampled range, indicating gene flow was restricted, especially between separate drainages. Two widely divergent regional groups which had high ATPase6 sequence divergence and approximately concordant patterns at allozyme loci were identified. Interestingly, the groups mirrored previous taxonomic designations. There was also significant subdivision among drainages within regional groups. For example, the adjacent Mulgrave-Russell and Johnstone drainages had individuals with haplotypes that were reciprocally monophyletic and had large allozyme frequency differences. This allowed me to examine the patterns of genetic differentiation among populations within drainages of two essentially independent, but geographically close systems. There was as much allozyme differentiation among populations within subcatchments as there was between subcatchments within drainages, and significant isolation by distance among all populations sampled within a drainage. This suggested that the estuarine confluence between subcatchments was not a barrier to P. signifer, but that distance was an important component in the determination of the distribution of genetic diversity within drainages in P. signifer. There were three main areas of investigation for C. stercusmuscarum: comparing upland and lowland streams of the drainages in north Queensland, investigating the consequences of eustasy on coastal margin populations and examining the intriguing distribution of the two putative sub species, C. s. stercusmuscarum and C. s. fulvus in south east Queensland. First, as populations in upland areas of east coast flowing rivers are above large discontinuities in the river profile, their occurrence is presumably the result of gene flow to and / or from lowland areas, or the result of invasions via the diversion of western flowing rivers. Concordant patterns at both genetic markers revealed that the latter possibility was the most likely, with fixed allozyme differences between upland and lowland populations, and large mtDNA sequence divergence. Indeed, it appeared that there may have been two independent invasions into the upland areas of rivers in North Queensland. Second, lowland east coast populations also had large, although not as pronounced, levels of population subdivision. Lack of isolation by distance, but with a concomitant high level of genetic differentiation among many comparisons, was consistent with a scenario of many small, isolated subpopulations over the range. Interestingly, widespread populations in central Queensland coastal populations (drainages which receive the lowest rainfall) were relatively genetically similar. This was consistent with the widest part of the continental shelf which at periods of lower sea level apparently formed a large interconnected drainage, illustrating the effect of eustatic changes on populations inhabiting a continental margin. Third, putative C. s. fulvus in lowland coastal Queensland drainages were genetically more similar to a population of C. s. fulvus collected from a tributary of the Murray-Darling (western flowing) than they were to adjacent putative C. s. stercusmuscarum. This implied that populations in south east Queensland, north to approximately the Burnett River, appeared to be derived from western flowing streams, and not via dispersal from other lowland east coast populations. Determining the relative importance of intrinsic and extrinsic factors to the development of population genetic structure is a difficult task. The present study demonstrated that the species with the highest dispersal potential had the lowest levels of genetic differentiation, waterfalls can limit gene flow, eustasy acts to join and separate populations leading to complex genetic patterns and that drainage rearrangements are important in determining the distribution of genetic diversity of populations now inhabiting isolated drainages. A difficulty with generalising about population genetic structure in obligate freshwater animals is the unique history of not only each drainage, but also the streams within that drainage and the idiosyncratic biological dynamics of the populations inhabiting those drainages.

Gli stili APA, Harvard, Vancouver, ISO e altri

49

my, marina@umt edu, e Marina Hassan. "Parasites of native and exotic freshwater fishes in the south-west of Western Australia". Murdoch University, 2008. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20090720.141418.

Testo completo

Abstract (sommario):

Fewer than 200 fish species are found in freshwater habitats in Australia, of which 144 are confined exclusively to freshwater. At least 22 species of exotic freshwater fish have been introduced into Australia, and 19 of these have established self-sustaining populations. However, the parasite fauna of both native and exotic freshwater fishes in Australia is poorly known. This is particularly the case in the south-west of Western Australia, where there have been no previous comprehensive studies of the parasites of 14 native species and nine or more exotic species of fish found in freshwater habitats. This study represents a survey of the parasites of freshwater fishes in the South West Coast Drainage Division and reports 44 putative species of parasites in 1429 individual fishes of 18 different species (12 native and six exotic) from 29 locations. Parasites were found in 327 (22.88%) fishes, and of the infected fishes, 200 (61.16%) were infected with only one species of parasite and 127 (38.84%) were infected with two or more species of parasites. For helminth and arthropod parasites, which were more comprehensively surveyed than protozoan and myxozoans, I found 37 species compared to 77 species found in a recent study of fishes from the East Coast Drainage Division. The present study demonstrated that parasitic infection was significantly more common in native fish species (mean prevalence of infection with any species of parasite = 0.36 ± 0.09) than in exotic fish species (0.01 ± 0.12). Parasites were found in all native fish species, but in only two exotic fish species that were examined. Parasite regional and component community diversity were estimated by species richness (the number of species, S) and by an index of taxonomic diversity (HT). Both parasite species richness and parasite taxonomic diversity were significantly greater in native fish species (mean S = 10.5 ± 2.3; mean HT = 1.19 ± 0.14) than in exotic fish species (mean S = 1.6 ± 3.3; mean HT = 0.27 ± 0.20). These relationships were consistent over all geographic locations that were sampled. The reduced parasite load of exotic species compared to native species has been previous reported across a wide range of taxa. It is thought to arise partly because founding populations of hosts have a low probability of harbouring the species total parasite fauna, and partly because parasites that infect introduced exotic species may not be able to maintain their life cycle in the new environment. It has been suggested that a reduced parasite load increases the competitive ability of exotic species compared to native species (the parasite release hypothesis) and this may partly explain the abundance and apparent competitive success of exotic over native species of freshwater fish in the South West Coast Drainage Division. For native species of fish, there were major differences among species in both prevalence of parasitic infection and parasite community diversity, but this variation was not related to fish size, whether the fish were primarily freshwater or primarily estuarine, or whether they were primarily demersal or pelagic. In this study, I report two new parasites in south western Australian waters. Both are copepod parasites; Lernaea cyprinacea and a new species of Dermoergasilus. The Dermoergasilus appears to be native to the south-west of Western Australia and has been described as Dermoergasilus westernensis. It differs from previously described species in the genus principally by the armature of the legs. This new species was found on the gills of freshwater cobbler, Tandanus bostocki and western minnow, Galaxias occidentalis in two different river systems. Lernaea cyprinacea is an introduced parasitic copepod found on the skin and gills of freshwater fishes in many areas of the world. The parasite has not previously been reported in Western Australia. We found infestations of L. cyprinacea on four native fish species (G. occidentalis; Edelia vittata; Bostockia porosa; T. bostocki) and three introduced fish species (Carassius auratus; Gambusia holbrooki; Phalloceros caudimaculatus) at two localities in the Canning River, in the south-west of Western Australia. The parasite has the potential to have serious pathogenic effects on native fish species, although it appears to be currently localised to a small section of the Canning River. Over all localities from which fishes were sampled in the present study, the proportion of native freshwater fishes with parasitic infections and the component community diversity of the parasite fauna of native fishes were both negatively related to habitat disturbance, in particular to a suite of factors (river regulation, loss of riparian vegetation, eutrophication and presence of exotic fish species) that indicate increased human usage of the river and surrounding environment. The reduced parasite load and diversity in native fishes from south-west rivers with greater human usage was due principally to the loss of a number of species of trematode, cestode and nematode endoparasites which use fishes as intermediate hosts. Other studies have also found that endoparasites with complex life cycles are most likely to be adversely affected by environmental changes, presumably because any environmental changes which impact on either free-living parasite stages or on any of the hosts in the complex train of parasite transmission will reduce parasite population size and may cause local extinction of the parasite species. The most heavily infected species of native freshwater fish in the South West Coast Drainage Division was T. bostocki with 96% of all individuals containing at least one species of parasite. As with most freshwater fishes of south-west Australia, T. bostocki is limited in its distribution to waterways with relatively low salinity. The degree of parasitism and histopathology of internal and external organs in T. bostocki from the Blackwood River was examined over a period of rapid, seasonal changes in water salinity. As salinity increased, the infracommunity richness and prevalence of ectoparasites on the skin of fishes decreased, while the infracommunity richness and prevalence of endoparasites increased. This was associated with a decrease in histopathological lesion scores in the skin and an increase in histopathological lesion scores in internal organs, particularly the intestine. I hypothesise that the seasonal spike in salinity had two contrasting effects on parasitic infections of T. bostocki. Firstly, it increased the mortality rate of parasites directly exposed to water, leading to a decrease in ectoparasitic infection and associated pathology. Secondly, it suppressed immune function in fish, leading to a decreased mortality rate of parasites not directly exposed to water and a more severe pathological response to endoparasitism.

Gli stili APA, Harvard, Vancouver, ISO e altri

50

Mondol, Md Rashedul Kabir. "Population Connectivity of Two Australian Freshwater Fishes in a Large Tropical Dendritic River Network". Thesis, Griffith University, 2016. http://hdl.handle.net/10072/365654.

Testo completo

Abstract (sommario):

Freshwater fishes are often characterized by extensive population genetic subdivision and low genetic diversity and are ideal subjects for investigating contemporary patterns of dispersal and subsequent gene flow. In lotic systems, different riverine architecture, variable hydrology and species biology influence genetic diversity and population structure in resident species. Stream-dwelling species often display greater levels of gene flow within drainages or catchments or sub-catchments than between them due to complexity of stream order and the isolating nature of these systems by land or sea. However, the relative importance of these attributes in driving population structure at spatial scales remains poorly understood for many freshwater species. Study on the effects of riverscape in shaping population structure is very important to identify management or conservation units and to undertake habitat restoration measures. The Daly River is one of the largest river networks in the wet-dry tropics of Northern Australia and shows variability in hydrology. This river has a complex arrangement of habitats and heterogeneous landscape features (e.g. slope, elevation) across the catchment area. There are also instream physical barriers like waterfalls, cliffs, road crossings etc. that may hinder dispersal and subsequent gene flow.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Environment
Science, Environment, Engineering and Technology
Full Text

Gli stili APA, Harvard, Vancouver, ISO e altri

Tesi sul tema "Freshwater fishes"

Cita una fonte nei formati APA, MLA, Chicago, Harvard e in molti altri stili