M.Sc. / The Bushveld smallscale yellowfish, Labeobarbus polylepis (Boulenger, 1907), is an ecologically, socially and economically important species. These indigenous freshwater fish are found above an altitude of 600m, and occur in the Inkomati and Phongolo River Systems and the southern tributaries of the Limpopo River System. In the past, it was suspected that morphological differences exist between the different L. polylepis populations, due to the occurrence of the rubberlip formation of individuals from the Elands River. Specimens of five L. polylepis populations were collected from the Phongolo, Assegaai, Elands and Komati rivers and Ngodwana Dam, Mpumalanga, South Africa. A L. natalensis population was collected from the Umvoti River and used as an out-group. Nine meristic counts and 46 morphometric measurements were taken. The measurements were changed into percentage ratios based on the fork length of each individual. The data was statically analysed and includes Multidimensional scaling techniques (MSD’s) and Principle Component Analysis (PCA’s). Statistical analysis split the five populations into three groups. The one group consists of fish from the Phongolo and Assegaai rivers, the second group consists of fish from the Elands River and Ngodwana Dam and the third group is mainly Komati River fish. The third group is the only group that does not overlap with any other group. There were morphological differences between the groups, but they were not significant. The L. natalensis population is morphologically similar to L. polylepis populations obtained from the Phongolo and Assegaai rivers. Twenty enzyme coding loci in two L. polylepis populations from the Phongolo and Elands rivers were analysed by horizontal starch gel-electrophoresis. Electrophoretic analysis of heart, muscle and liver tissue samples revealed genetic variation at 15% (Elands River) and 35% (Phongolo River) of the protein coding loci studied. Average heterozygosity values based on Hardy-Weinberg expectation were 0.019 (Elands River) and 0.059 (Phongolo River), with a genetic distance value of 0.004 between these populations.

No description available.

No description available.

Anthropogenic influences on riverine ecosystems have led to numerous impacts that have compromised fish communities. Large European lowland rivers have been amongst the most impacted aquatic environments globally. However, paradoxically, these environments have also been amongst the least studied, due the inherent difficulties of studying fish in large, turbid, dynamic environments. Common bream Abramis brama (L.) populations are amongst those impacted by reduced lateral and longitudinal connectivity that are a consequence of modifications to large lowland rivers in Europe. Thus common bream in the lower River Witham, Lincolnshire, UK, were selected as a case study to examine how fish utilize these river systems. A literature review was carried out to assess the influence of human intervention on riverine ecosystems and their impacts on fish communities. In addition the use of telemetry techniques for studying fish populations was reviewed. An ecological assessment of the lower River Witham was carried out using data available from The Environment Agency monitoring and hydrological systems and data specifically collected during this study. The history of this highly modified lowland river was reviewed to give perspective, timescale and context to the degree of modification that has been undertaken on the river and its consequences. Chemical and biological water quality indicators showed improvements in the last twenty years. Fisheries data identified three species that had become locally extirpated in the lower river since the 1800s. The river is now roach dominated, but common bream are still present, possibly due to available lateral spawning habitats that provide surrogates for, and are functionally similar to, the lentic floodplain waterbodies of natural riverine ecosystems. Hydroacoustic surveys show that fish communities are aggregated and favour the upstream half of the lower river where the channel is more heterogeneous. Recent changes in river character have made traditional fishery assessments by seine netting less effective. Data collected during fish tracking studies are most valuable when the tagged fish are behaving naturally, thus the effects of tag attachment should not impact on the behaviour or well being of the fish. Acoustic telemetry was used to investigate the impacts of tagging, surgical inter-peritoneal implantation, and translocation of common bream. Fish were recaptured following surgery and the incision site photographed to assess healing, which was clean in all cases. All recaptured fish appeared to be behaving normally as they were part of large shoals of fish. On five separate occasions fish were tagged when other previously tagged fish were present allowing their behaviour to be compared in terms of the distances moved and linear range; there were no significant differences between the two groups indicating the tagging procedure to have no detectable impact on the short-term behaviour of the fish at the resolution of the tracking undertaken. Three recaptured fish were translocated ~35 km downstream; these fish appeared to exhibit homing behaviour, returning to the capture site between 6-24 days. Their level of activity (in terms of distance moved) did not significantly differ from non-translocated fish, but their linear range was larger. The distribution and habitat use of adult common bream was assessed by tracking their longitudinal and lateral movements over forty-three months, producing a dataset of over 3.1 million detections. A positive relationship between activity and temperature was revealed, with common bream moving greater cumulative distances during the warmer months and occupying a greater longitudinal proportion of the main channel. The occupancy of tributaries was related to temperature, with common bream entering shallow tributaries during rising temperatures in the spring, whilst a deeper, slow-flowing tributary was used more frequently during the cooler autumn/winter months. During the autumn, occupancy of this deeper tributary was positively related to flow rate, suggesting that common bream use this as a refuge from high main channel flow. The home range concept is at the centre of theoretical models to explain the spatio-temporal behaviour of a wide range of animals including fish. There are lots of different ways of expressing home ranges, including areas, but since rivers are principally linear systems, most range is reflected linearly. Home ranges were calculated for 100% and 90% of locations. Seasonal differences were identified with fish occupying larger home ranges during the spring and summer opposed to autumn and winter. Artificial water level manipulations, management actions for the control of flood risk, affected home range size with fish occupying smaller ranges at reduced winter levels than at increased summer levels. Analysis of when and how often individuals within a population interact with one another provides a method to study the social organisation of animals with the potential to reveal ecologically significant aspects that would otherwise have remained hidden. Network analysis and social network theory were used to examine the social interactions of the tracked fish. The extent of sociality appears to follow a normal distribution, such that there was no evidence of discrete classes of social/non-social fish. Fish were more social immediately after tagging and less social as time progressed, as such little evidence could be found to support the hypothesis that these groups of fish remained in each others’ company for extended periods. However, more active individuals were found to be more socially connected, but home-range size did not significantly affect sociality. The functions of these behaviours are discussed along with potential management and rehabilitation strategies for the lower River Witham and other heavily modified lowland rivers in order to meet good ecological potential/status under the Water Framework Directive (2000/60/EEC).

No description available.

Habitat temperature is a major determinant of performance and activity in fish. I examined the relationships between thermal response metrics describing growth (optimal growth temperature [OGT] and final temperature preferendum [FTP]), survival (upper incipient lethal temperature [UILT] and critical thermal maximum [CTMax]), and reproduction (optimum spawning [OS] and optimum egg development temperature [OE]) for 173 North American freshwater fish species. All metrics were highly correlated and associated with thermal preference class, reproductive guild and spawning season. Controlling for phylogeny resulted in an overall decrease in correlation strength, varying with metric pair relationship. ANCOVA and Bayesian hierarchical models were utilized to assess the influence of phylogeny on metric pair relationships. For both methods, FTP based metric pairs were weakly correlated within taxonomic family. Strong within family associations were found for reproduction metrics OS-OE. These results suggest that evolutionary history plays an important role in determining species thermal response to their environment.

Habitat temperature is a major determinant of performance and activity in fish. I examined the relationships between thermal response metrics describing growth (optimal growth temperature [OGT] and final temperature preferendum [FTP]), survival (upper incipient lethal temperature [UILT] and critical thermal maximum [CTMax]), and reproduction (optimum spawning [OS] and optimum egg development temperature [OE]) for 173 North American freshwater fish species. All metrics were highly correlated and associated with thermal preference class, reproductive guild and spawning season. Controlling for phylogeny resulted in an overall decrease in correlation strength, varying with metric pair relationship. ANCOVA and Bayesian hierarchical models were utilized to assess the influence of phylogeny on metric pair relationships. For both methods, FTP based metric pairs were weakly correlated within taxonomic family. Strong within family associations were found for reproduction metrics OS-OE. These results suggest that evolutionary history plays an important role in determining species thermal response to their environment.

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.

University of Technology, Sydney. Faculty of Science. / In the last 100 years there have been dramatic declines in the range and abundance of native freshwater fish in south-eastern Australia. These declines have been attributed to habitat loss and degradation (including river regulation, water quality, erosion/siltation, instream cover and riparian vegetation), alien fish species, overfishing, and the obstruction of fish passage. In south-eastern Australia there are 86 species of freshwater fish and 36 of these have some migratory component of their life history that requires free passage along streams. The migrations of these fish in this region have been inhibited or prevented by the existence of more than 1500 dams and weirs. To mitigate this impact there are only 69 fishways. Most of these fishways are based on designs suitable for the swimming ability and behaviour of salmonids from the Northern Hemisphere. There are, however, no native salmonids in Australia. I assessed one of these salmonid fishways, at Euston on the Murray River, for its suitability for passing native fish. Fish were trapped at the top and bottom of the fishway over eight paired days. Although this fishway has one of the lowest slopes of the older fishways, and therefore potentially one of the easiest to ascend, very few of the fish that entered the fishway could get to the top. For example, 777 +/- 238 [x +/- s.e.] golden perch (Macquaria ambigua) per day entered the fishway but only 4 +/- 2 per day were collected at the top of the fishway. This and other data highlighted two points: i) the ineffectiveness of the salmonid-type fishways for native fish; and ii) assessing fishways by counting fish at the top only, although widely used throughout the world, is insufficient to assess the performance of a fishway. Counts of fish from the top of a fishway can, however, be useful to monitor fish populations over time. An excellent example of this is provided by long-term monitoring of the Euston fishway, which shows massive declines in the upstream movements of silver perch (Bidyanus bidyanus), Murray cod (Maccullochella peelii peelii) and Macquarie perch (Macquaria australasica) between 1940-45 and 1987-90, indicating corresponding declines in the populations of these species. The failure of salmonid fishways for non-salmonid fishes has been a common experience throughout the world. It stems partly from a lack of knowledge of the migratory patterns of non-salmonid fish, and from a lack of quantitative experimental research into the swimming ability and behaviour of these fish in fishways. To redress this situation for south-eastern Australia, I tested fish in experimental fishways in a hydraulics laboratory. The fishway design tested was the vertical-slot fishway, which is a pool-type fishway where water flows between each pool via a vertical slot. The design was considered to potentially suit the hydrology of Australian rivers and the behaviour of native fish. For these experiments I selected fish species and life stages representative of the migratory fish fauna of the two major drainages of south-eastern Australia. For the south-eastern coastal rivers I chose juvenile Australian bass (Macquaria novemaculeata)[mean lengths of 40, 64 and 93 mm] and barramundi (Lates calcarifer) [43 mm]. These two species are catadromous, with the adults migrating downstream to the estuary to breed and the juveniles migrating upstream. For the large inland Murray-Darling river system I chose adult golden perch (Macquaria ambigua) [441 mm] and silver perch(Bidyanus bidyanus) [258 mm]. At the beginning of this study, adults of these two species were considered to be the main life stage migrating upstream. In the laboratory experiments fish were tested at different water velocities and probit analysis was applied to the proportion of fish that negotiated these velocities. I used this approach to produce values which I called the NV90 and the NV95, which are the maximum water velocities that 90% and 95% of the fish could negotiate in the fishway. For bass, barramundi and golden perch these values ranged from 0.7 to 1.8 m s-1. These values are well below the standard maximum water velocity for salmonid fishways of 2.4 m s-l. The silver perch results were too variable to analyse. The data obtained from the laboratory experiments were used by water resource agencies to build eight new vertical-slot fishways in coastal and inland rivers of southeastern Australia. One of the largest of these new fishways was at Torrumbarry Weir on the Murray River, which consists of 38 pools, each 3 m long, ascending a 6.5 m high weir. The fishway, if successful, would provide access to 350 km of habitat above the weir. To determine whether or not the fishway was successful in passing native migratory fish it was assessed for 2.5 years by: i) sampling monthly above and below the fishway with a standard set of independent, replicated nets; and ii) sampling within the fishway. The netting showed that there were major aggregations of migratory fish below the weir when the fishway was not operational. However, when the fishway was completed and operational, 13 months after the commencement of sampling, there were no further major aggregations of migratory fish below the weir. These data, combined with high numbers of fish successfully ascending the fishway, indicated the success of this vertical-slot fishway design. It was estimated that from February 1991 to June 1993 20,7 14 native fish and 16,595 alien fish (all carp [Cyprinus carpio]) had successfully ascended the fishway. Sampling at the top and bottom of the fishway showed that the fishway passed almost all the species and sizes classes of native migratory fish, except for Australian smelt (Retropinna semoni). The latter is a small species 15 to 40 mm long that only entered the lower few pools of the fishway. The widespread distribution of this species indicates the migration is facultative. Experiments within the fishway showed that the laboratory experiments had underestimated swimming ability. However, it was discovered that fish still needed over 1.5 hours to ascend the full length of the fishway. In addition, some species only migrated upstream during daylight and if their ascent of the fishway was not completed in daylight the fish moved back down the fishway. I concluded that the original water velocity criterion from the laboratory experiments was appropriate and that future fishways need to consider ascent time and fishway length as well as water velocity. I also concluded that it is more difficult to obtain realistic results from 'off-site' experiments, where fish are transported to a laboratory or other facility, than from in situ experiments where naturally migrating fish are used and are not handled until the end of the experiment. Sampling at Torrumbarry Weir provided detailed information on the biology of the migratory fish species, which is essential to designing effective fishways. Carp(Cyprinus carpio), an introduced or alien species, and bony herring were newly identified as migratory, and golden perch and silver perch were confirmed as migratory. A major finding was that 95% of golden perch and 87% of silver perch moving upstream were immature fish. Previously the upstream movement of immature fish in this river system was considered insignificant. Fortunately the conservative water velocities in the Torrumbarry fishway accommodated these smaller fish(approximately 100 to 300 mm in length). The reason for the large numbers of immature fish migrating upstream is not clear, but it may be to optimise feeding, enhance colonisation, or to compensate for the downstream drift of the pelagic eggs and larvae. Migration of all species was seasonal. Spring, summer and early autumn were the main periods of upstream movement for native fish, and carp moved upstream in spring and early summer. Migration of carp was stimulated by rising water temperature only, but golden perch and silver perch were stimulated to move upstream by small changes in river levels. This small scale variation in streamflow is frequently suppressed by river regulation, and this is likely to have contributed to the significant decrease in the numbers of migrating native fish. Upstream migration of all species often occurred during low flows, as well as higher flows. This also occurs in coastal rivers of southeastern Australia. For both the coastal and inland rivers of this region it will be important to design fishways and environmental flow releases to accommodate this aspect of fish migration and the often semi-arid hydrology of these streams. Golden perch and silver perch were aged using sagittal otoliths and validated using known-age fish. The data showed that the immature fish were all over one year old, suggesting that younger fish are not migrating upstream. More research is needed to determine the location and habitats of the less than one year old fish. Ageing and examination of gonads indicated the size and age at maturity for these fish. This suggested that minimum size limits currently used to regulate the recreational fishery are not allowing fish to reach maturity. Golden perch and silver perch were found to be long-lived fish, up to 26 and 27 years respectively. Interestingly, samples of these two species from other rivers within the Murray-Darling river system show that the maximum sizes of these fish can vary significantly between rivers, suggesting that the ecology of different rivers within this large river system varies considerably. The development of fishways for non-salmonid fishes throughout the world has frequently met with failure. From the work in the present study and from reviewing other work I suggest there are five steps for the development of effective fishways. 1. Determine which fish species are migratory: - it is important to identify the smallest and largest fish that are migratory, as this affects the initial choice of the size of the fishway to test. 2. Test fish in an experimental fishway: - in situ experiments are recommended; - avoid handling of fish before and during experiments. 3 Design the fishway: - first decide on the location of the fishway entrance; - extrapolate research results with caution; - do not reduce pool sizes from the experimental model; - avoid tunnels; - design the fishway to operate over the full range of flows during which fish migrate. 4. Link the fishway with the operation of the dam or weir: - maintain flow and temperature regimes that stimulate migration; - manage flow releases over the spillway to guide fish to the fishway entrance. 5. Assess the fishway: - use quantitative and relevant performance criteria to assess the fishway and not only counts of fish from the top of the fishway. The most common strategy in the past has been to design the fishway and ignore steps 1, 2, 4 and 5. With fishways being increasingly recognised as important tools in the rehabilitation of aquatic biota in temperate river systems, and as a potential tool in the development of water resources in tropical rivers, it is essential that they are appropriately designed, constructed, and assessed. Otherwise the mistakes of the past will very likely be repeated.

The Murray-Darling basin is the largest river system in Australia with significant economic, social, recreational and cultural value. It supplies water for drinking and agriculture to a large inland area of the eastern and southern states of Australia. It is also the ultimate sink for many environmental contaminants that result from human activities within the catchment. Aquatic organisms live intimately with their environment and may be continuously exposed to these contaminants through the water column or the food chain. Some chemicals are bioaccumulated and biomagnified in tissue to reach high body burdens. Populations of native fish species within the Murray-Darling basin have been in decline since human settlement, yet little is known about the lethal and sublethal effects of environmental pollutants on native freshwater fish and many of the Australian water quality guidelines are based on data from exotic fish species. Researchers have correlated levels of pollution with immune dysfunction and an increased incidence of disease amongst wildlife populations. Many of the pollutants of the Murray-Darling basin have known immunotoxicity in both mammals and exotic fish species. The immune system is a sensitive target organ because, in order to maintain integrity, it requires constant renewal through the rapid proliferation and differentiation of cells. Efforts to increase numbers of native fish in the wild have led to an aquaculture industry that produces fingerlings for the restocking of waterways. In more recent years, this industry has matured and now produces table-size native freshwater fish for local and international markets. Although the industry has researched areas of reproduction, nutrition and stocking, there is little understanding of the immunology or immunotoxicology of Australian freshwater fish. This research project investigated the immunology of three large native fish species (i.e. 2 Murray cod, golden perch and silver perch), which are the basis of the native freshwater aquaculture industry. Additionally, a small fish species native to the basin (i.e. crimsonspotted rainbowfish) was studied as an alternative to the use of large fish. Of the four species, Murray cod possessed characteristics that made it an excellent candidate for ecoimmunotoxicity testing.