Dissertations / Theses on the topic 'Native Australian freshwater fish'

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.

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.

Physiological experiments were conducted to measure the effects of low pH water upon Na⁺ fluxes and swimming performance in east coast neutral water banded kokopu, and west coast banded kokopu living in naturally acid water. This allowed comparisons to be made regarding the relative acid tolerance between the two population stocks. A morphological study of the gills using scanning electron microscopy and transmission electron microscopy was carried out on a limited number of fish to compare gill structures of east coast acid and non acid exposed fish with west coast fish. East coast kokopu from neutral water showed a reduced sodium influx on the first day of exposure to pH4 water. This was accompanied by a reduction in passive loss or efflux. After 4 days at pH4 influx recovered allowing the fish to approach sodium balance. West coast fish showed no significant change in influx upon introduction to pH7 water and maintained influx values in pH4 water near those measured for control fish. For east coast fish, swimming performance was significantly impaired on the 2nd swimming trial when pH was lowered from 7 to 4. On the third swim with the pH returned to 7, Ucrit was similar to the initial value. West coast banded kokopu showed a significant increase in performance between trial one and three and were unaffected by pH7 water, matching performances measured in control fish. Gills from east coast acid exposed fish resembled west coast fish in that the trailing edges of the lamellae were swollen due to the large numbers of chloride cells which were present to a point approximately half way up the lamellar edge. Microridges were present on the apical surfaces of the chloride cells of east coast control fish which contrasted with the microvilli structures observed in west coast and acid exposed east coast fish. The microvilli structures present on the chloride cells of west coast and east coast acid exposed banded kokopu appeared to assist in the anchorage of mucus to the apical surface of the cell.

The arrival of a non-native species to has the potential to shape native communities by influencing ecological interactions such as predation, foraging, competition and disease transfer. A designation of invasive is applied to an introduced non-native species that has the potential to threaten the continued wellbeing of a native species, pose a risk to human health or negatively impact the economy. The European bullhead (Cottus perifretum) is a freshwater benthic-dwelling fish that is native to England but considered invasive in Scotland. The species was first reported in Scotland in the 1950's and thriving populations are now established in the waters of the Clyde, Forth and Tweed catchments. Bullhead presence is thought to negatively impact native stone loach (Barbatula barbatula) and brown trout (Salmo trutta) parr, due to shared preferences for habitat and prey resources. They are also thought to prey upon the eggs of native Atlantic salmon (Salmo salar) and brown trout, two species that are of high commercial value in Scotland. In other areas of introduction, bullheads have been found to increase parasite infection rates in native fishes. The species therefore has the capacity to incite competition and alter parasite/host interactions in areas of introduction, to the potential detriment of native fauna and the Scottish economy. The European bullhead has been the subject of considerable taxonomic scrutiny in recent years, resulting in its reclassification as a species complex. What was once considered a single species with a distribution encompassing Europe, Russia, Asia and Scandinavia, has been shown to consist of at least 15 distinct species. Genetic examination of bullheads from England confirmed the presence of Cottus perifretum, not Cottus gobio as traditionally listed in all UK literature and legislation. Native English bullhead is currently protected under Annex II of the European Commission Habitats Directive 92/43/EEC, based on the historic assumption that the species present is C. gobio. Analysis of the taxonomic identity of Scottish bullheads has remained outstanding. In this study the invasive status of bullhead was explored by examining feeding and parasitological interactions between bullheads and native freshwater communities in south-east Scotland. An assessment of the feeding preferences of native brown trout and stone loach in the presence and absence of bullheads tested competition for prey resources. Parasitological interactions were investigated by examining the shared parasite fauna of bullheads and native fish and invertebrate species. Bullheads from the Clyde and Forth catchments were analysed to provide a molecular and morphological description of this introduced species. Phylogenetic analysis of COX1 sequences obtained from Scottish bullheads, and a pair-wise distance calculation based on a Kimura 2-parameter model, showed that samples clustered in a distinct clade with English C. perifretum. Significant intraspecific variation was reported in all morphological features examined, but pooled data also revealed a resemblance to the published description provided for C. perifretum. Scottish bullhead is therefore confirmed to be an introduced pocket of the native English species, which is considered under threat in some areas due to habitat modifications and population decline. Comparisons between the dietary compositions of bullheads, brown trout and stone loach showed that the prey selection of brown trout and stone loach varied in the sample locations that contained co-occuring bullheads, when compared to locations where bullheads were absent. However, no direct evidence of trophic competition between bullheads and either brown trout or stone loach was reported. An examination of parasitological interactions recovered eight parasite species from four distinct taxonomic groups in total, of which four species (Echinorhynchus truttae, Apatemon gracilis, Diplostomum volvens and Raphidascaris acus) were shared between bullheads and one or more native fishes. Echinorhynchus truttae was also shared with gammarid crustaceans. Bullhead presence was found to coincide with D. volvens infections in European minnow (Phoxinus phoxinus) and a reduced prevalence of E. truttae in brown trout. Diplostomum volvens was only reported from minnow found in sites with bullheads, strongly suggesting bullheads were responsible for introducing this parasite to native minnows. Bullheads functioned as an alternative host for E. truttae, diluting brown trout parasite loads and reducing overall infection rates in sites where bullhead and brown trout co-exist. The findings reported for both feeding preference and parasite burdens in the presence and absence of bullheads suggest that bullheads do have some effect on the ecology of native species, but these are considered minimal and unlikely to impact the long-term survival of native species. Eradication of Scottish bullhead may contradict the conservation effort that is currently in place. Given the current lack of evidence to validate bullhead's invasive qualities and the recent confirmation of its genetic lineage, revisiting the designation of the bullhead as invasive is warranted. Active eradication should be treated with caution until a significant negative impact can be proven.

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.

Global climate change models indicate that a rise in temperature and reduction in rainfall in the Western Cape Province of South Africa is inevitable and unavoidable. Within the Western Cape lies the Cape Floristic Region (CFR); a biodiversity hotspot with high levels of endemism. This includes its freshwater fish assemblage. Whereas the current greatest threats to native fish biodiversity are habitat degradation and invasion by non-native species, predicted climate change is likely to further impact fish communities negatively. As a master abiotic variable in aquatic ecosystems; temperature influences the fitness, behaviour, and life-histories of aquatic biota. Thermal alteration may therefore affect sensitive fish species. The upper thermal limit, determined via the critical thermal method, has been validated as a measure of thermal sensitivity. To better understand the impacts of climate change on the native fish of the CFR, upper thermal limits (critical thermal maxima/CTmax) were determined for seven native species of freshwater fish. Thermal preferences were also determined for five of these species using the acute gradient tank approach to elucidate thermal habitat preferences. Species that were identified by the IUCN as vulnerable, endangered, or critically endangered were selected from the four main families of native fish in the CFR (Anabantidae, Austroglanidae, Cyprinidae, and Galaxiidae), from four Rivers. Overall, Cape galaxias (Galaxias zebratus), Breede River redfin (Pseudobarbus burchelli), Berg River redfin (Pseudobarbus burgi), Clanwilliam redfin (Pseudobarbus calidus), and fiery redfin (Pseudobarbus phlegethon) were found to be most sensitive to increased temperature (CTmax= 29.8-32.7⁰C). Clanwilliam rock-catfish (Austroglanis gilli) and Cape kurper (Sandelia capensis) were found to be moderately sensitive (CTmax= 33.0-35.3⁰C). Similar trends were found using the thermal preference approach as CTmax and thermal preference were found to correlate well. The results were related to in-situ water temperature, which influenced both parameters. Thermal tolerances and preferences of all the native species exceed that of invasive salmonids (Onchorynchus mykiss and Salmo trutta). However, non-native centrarchids (Micropterus spp.) are more thermally tolerant, indicating an increase in threat by warm adapted non-natives. These data suggest that species interactions and distributions are likely to undergo substantial changes in response to elevated water temperature.

Vertebrate populations are subjected to novel anthropogenic stressors that are expected to multiply exponentially in the future. Introductions of nonnative species and human-altered hydrology are among these stressors to native species communities. The Rocky Glades, located in Everglades National Park, may serve as a population sink for native species that typically do not survive the altered hydrology of the dry season, and as a source of nonnative species that may be better adapted to chronically stressful conditions. In the seasonally-flooded Everglades, the nonnative African Jewelfish invaded in the 1960s and has since shown rapid range expansion. African Jewelfish are aggressive and territorial, thus they are predicted to be more successful at acquiring space and resources, and may displace native Sunfishes. I monitored assemblages of fish across time in experimental mesocosms and solution holes and quantified survivorship and body condition of both natives and nonnatives. Overall, native Sunfish did poorly while nonnatives had higher survivorship over the course of the dry season. Unexpectedly, no evidence indicated that Jewelfish reduced survival of native Sunfish. I compared aggressive interactions between native Dollar Sunfish and nonnative African Jewelfish in Sunfish populations either sympatric or allopatric with Jewelfish. Sympatric Dollar Sunfish were twice as likely to approach African Jewelfish as allopatric ones. My study suggests native species can survive invasion through behavioral adaptation to nonnative competitors. Characterizing interactions between native and nonnative species and identifying their niche use can assist in understanding the challenges of native species conservation in the face of species invasions.

Habitat destruction/alteration and non-native species are widely considered the two most serious threats to biodiversity within freshwater ecosystems, which are among the most threatened in the world. I examined the effects of these factors, specifically focusing on land use and non-native species as drivers of abundance patterns of native fishes in the highly invaded and anthropogenically impacted New River basin (NRB) in the Appalachian region of the United States. In chapter 2, I examine current native and non-native species abundance patterns related to the highly variable land-use mosaic present across the NRB, with specific focus on the species-specific effects of intensive land-use practices (agriculture and urbanization) at varying spatial extents (upstream watershed, upstream riparian, and local riparian). In chapter 3, I investigate historical context of basin-wide and site-level abundance spread and decline of natives and non-natives in the upper and middle New River basin (UMNR) over the past 60+ years. Finally, in chapter 4, I partition the variation in native species abundance explained separately by land use and non-native species to determine which factor might be most influential in describing abundance distributions of UMNR native fishes over the past 20+ years. My results indicate widely varying responses of native species to various combinations of intensive land use and non-native species across contributing watersheds and widespread biotic homogenization and native species declines over the past 60+ years. These declines include reductions in unique communities and endemic species provided little consideration or protection under current conservation law. I suggest potential avenues for improvement of conservation actions to help preserve these unique species and communities based on their responses to various land-use and non-native species stressors. My study framework should be broadly applicable to other drainages and should provide opportunities for early identification of potential native species declines and the stressors that may be contributing to them.
Master of Science
Freshwater fishes are experiencing world-wide declines that have the potential to cause major negative ecological and economic impacts. Two of the biggest contributors to fish declines are habitat destruction and non-native species introductions. I examined populations of numerous fish species in the New River basin (NRB) in the Appalachian region of the United States to identify declining native species and determine how intensive land use (one type of habitat destruction) and non-native species may be contributing to these trends. My results suggest that nearly half of the native species occurring in the NRB may be experiencing widespread reductions in abundance. As a result of these declines and the spread of a few common native and non-native species, fish communities across the NRB are becoming less unique over time. Land-use changes, such as agricultural and road development near streams, which contribute to increased soil erosion and run-off of silt and sand into streams, could be causing broad habitat changes that lead to diminished populations of sensitive species and overall local and regional fish diversity. While no single non-native species may be held responsible for all native fish species declines in the NRB, complex interactions, such as competition and predation, between many natives and non-natives altogether could be contributing to many native fish declines. Farmers and other landowners can help to prevent future fish declines by re-establishing natural vegetation, such as trees, along streambanks and implementing other practices, such as cattle fencing, that reduce the streambank and soil erosion that harms fish habitat. Other stakeholders, such as anglers, can help prevent future native fish declines by limiting introductions of additional non-native species. For example, these stakeholders could avoid releasing aquatic pets and live bait into NRB streams. These practices would help limit future negative impacts caused by non-native species.

The Murray cod (Maccullochella peelii peelii Mitchell 1838) is Australia�s largest freshwater fish. Once highly abundant in the Murray-Darling river system, populations have drastically declined in recent decades. Many causes for this decline have been proposed, including over-fishing, habitat loss and altered river flow regimes. This study hypothesised that elevated salinities have led to selective mortality in some developmental stages, which have in turn depleted stock recruitment and adult populations. The objectives of this study were to determine the optimal, threshold, upper sublethal and lethal salinities for development of eggs, yolk-sac larvae, fry and fingerlings of M. peelii peelii. Investigation the impact of salinity on fertilisation utilised gametes of trout cod (M. macquariensis, Cuvier 1829) instead of M. peelii peelii. Studies were carried out in a controlled laboratory environment using test media prepared from commercial sea salt. The results showed that the eggs of the trout cod hatched only when fertilised and incubated in freshwater, and only larvae hatched in freshwater survived through the yolk absorption period of 12 days. Yolk utilisation efficiencies were not significantly different among the salinities of 0-0.30 g/L. There was no effect of pre- or post- fertilising processes on the salinity tolerances of yolk-sac larvae. No larvae survived at salinities higher than 0.30 g/L during the yolk utilisation period. Lethal salinity concentration in Trout cod and Murray cod larvae was exposure time dependent. The 1 day LC50 of the larvae was 1.97 and 2.33 g/L respectively, compared with the 12 day LC50 values of 0.50 and 0.35 g/L respectively. The threshold (no effect level) salinities of larvae of Trout cod and Murray cod were 0.46 and 0.34 g/L respectively at 12 days exposure. The salinity sensitivities of fry of Murray cod were moderated by increasing pH between pH 6.2 and 8.8, and stimulated by increasing temperatures from 15 to 30°C. The optimal salinity was only slightly affected by temperature. The threshold and upper sublethal salinities varied slightly depending on feeding regime. The salinity sensitivities of fingerlings of Murray cod were: LC50 = 13.7 g/L; optimal salinity from 4.6 to 5.0 g/L ; threshold salinity from 5.9 to 7.4 g/L, and upper sub-lethal salinity from 9.2 to 9.9 g/L � with the range in all cases affected by acclimation period salinity. The blood osmolality at LC50 of the fingerlings was 444 mOsmol/kgH2O or equivalent to 14.2 g/L, and the dehydration rate was 4.8%. The osmolality increased significantly in salinities higher than 9.0 and 6.0 g/L when fish were exposed for a period of 1 day and 41 days respectively. The oxygen consumption increased significantly in salinities higher than 8.0 g/L. Distortion of the notochord and corrosive skin syndrome were major symptoms describing sub-lethal effects found in the embryos, and fry and fingerlings of Murray cod respectively. Noting the risks of extrapolating directly from laboratory to field conditions, it is predicted that when salinity in natural habitats increases above 0.34 g/L a significant impact on Murray cod recruitment will result.

Stocking herbivorous aquatic organisms in wastewater treatment ponds specifically to control phytoplankton biomass and reduce suspended solids can provide small, rural communities with inexpensive, secondary wastewater treatment. The capability of several native fish species and the freshwater mussel, Elliptio complanata, to reduce suspended solids and phytoplankton was compared in laboratory and field enclosure experiments. Fathead minnows (Pimephales promelas), gizzard shad (Dorosoma cepedianum), and the common carp (Cyprinus carpio) had either no effect, or significantly increased suspended solids levels. None of the fish species consistently reduced concentrations of typical wastewater algal taxa. The ineffectiveness of fish was attributed to numerous algal characteristics such as cell size, shape, relative abundance, resistance to digestion, and palatability. In contrast, E. complanata consistently and substantially reduced both suspended solids and algae concentrations in wastewater. Small-sized algae and suspended particles were either directly assimilated, or removed from suspension as pseudofeces, further promoting clarification. The proportion of suspended solids and algae concentrations removed per individual mussel declined with increasing densities of mussels. Declines in suspended solids and algae attributable to mussel filtration were best described by semilogarithmic regression equations. Mean filtration rate of E. complanata ranged from 53 ml/h/mussel for colonial blue-green algae, to 134 ml/h/mussel for smaller green algae. The results of this study suggest that freshwater mussels can effectively control suspended solids and algae in eutrophic environments.
Master of Science

Black Carp (Mylopharyngodon piceus) is an invasive fish species native to Asia that has become increasingly abundant within the Mississippi River Basin during the past decade. Originally introduced to control snails that are an intermediate host for trematode parasites of fishes in aquaculture ponds, Black Carp are now present in several rivers in the U.S. and represent a potential threat to threatened and endangered mussel populations. Black Carp have historically been classified as molluscivores; however, a recent study that examined gut contents of Black Carp collected from the Mississippi River Basin indicated that Black Carp are opportunistic consumers that prey upon a wide variety of invertebrates and are flexible in their feeding modes. Despite the potential for Black Carp to compete with native riverine fish species for invertebrate prey, only one published study has compared Black Carp trophic position with that of native fishes in a small portion of the Black Carp’s invaded range. Therefore, the objectives of this study were to assess trophic overlap between Black Carp and two fish species native to the Mississippi River Basin using isotopic niche analysis and gut contents analysis. Dorsal muscle tissue samples were collected from Black Carp, Freshwater Drum (Aplodinotus grunniens), and Blue Catfish (Ictalurus furcatus) and analyzed for δ13C and δ15N to assess each species’ isotopic niche. Freshwater Drum and Blue Catfish gut contents were also removed and analyzed and compared to published Black Carp stomach contents data. Gut contents analysis indicated differences in diet composition between Black Carp and the two native fish species. Chironomidae had the highest frequency of occurrence (67%) and percent of taxa by number (47%) for Freshwater Drum. Trichoptera had the highest frequency of occurrence (58%) and percent of taxa by number (30%) for Blue Catfish, and Gastropoda had the highest frequency of occurrence (16.5%) of any specific prey taxa for Black Carp. Black Carp showed low isotopic niche overlap (≤47%) with both native species when muscle tissue δ13C and δ15N data from all fish collection locations were combined and when assessment of isotopic niches was restricted to the subset of locations where all three species were collected. Isotopic niche overlap was also low (10-48%) between Black Carp and both native species when isotopic niches were compared at individual collection locations. Intraspecific isotopic niche overlap among fish collection locations was highly variable (0-69%) within each of the three species, highlighting the need to assess interspecific isotopic niche overlap by collection location. Broad isotopic niches exhibited by Black Carp in the Mississippi River and tributaries are indicative of substantial trophic diversity among individuals and use of multiple basal energy sources, consistent with a recently published study which found that Black Carp diet composition differed among individuals and that Black Carp consumed a variety of invertebrates, including non-benthic taxa.

Interactions between non-native yabbies (Cherax albidus) and indigenous marron (Cherax tenuimanus) in the south-west of Western Australia are not well understood. While there is abundant evidence to suggest that invasive freshwater crayfish are detrimental to native species, the nature and degree of impact on marron populations by exotic yabbies remains unclear. Researchers have hypothesized that invasive species make faster and more appropriate use of information about their environment than native species. This greater behavioural plasticity can result in displacement of indigenous species, successful colonisation by invaders, and subsequent disturbance to natural ecosystems and representative biodiversity.
The research presented in this thesis examines the behavioural responses of an indigenous crayfish (C. tenuimanus) and an invasive crayfish (C. albidus) to waterborne odours derived from food, alarm sources and finfish predators. This study was undertaken to assist in the understanding of predatory and competitive interactions between indigenous and non-indigenous crayfish and fish predators, with particular relevance to Western Australia. Predation and competition are major forces influencing community structure in ecosystems; therefore knowledge of competitive and predatory interactions will be of benefit when considering future translocation policies.
Behavioural trials were conducted in two culture systems (54 L aquaria and a 70,000 L mesocosm), where marron and yabbies were exposed to a range of water-borne odours from finfish predators (silver perch and Murray cod), with and without competition from conspecific and heterospecific crayfish. A number of variables likely to influence crayfish behaviour were investigated: strength of chemical odour; crayfish size, gender, diurnal and nocturnal activity patterns; predator size; prior-residence; suitable habitat/shelter; and feed availability.
A key innovation in this research was the high replication in the aquarium-based observation trials using a Latin Cube design, which resulted in greater statistical strength and lower variability. More importantly, this research deviated from the tradition of exclusively using the ‘individual crayfish’ approach for odour-detection experiments and tested these results in a 70,000 L communal observation tank. This was an important development in crayfish behavioural experimentation, particularly as several key findings from the individual crayfish approach were confirmed in a multi-species environment.
Results from this study supported the hypothesis that invasive crayfish species make more appropriate use of a wider range of information about their environment than native crayfish species. Yabbies were found to possess behavioural characteristics not present in marron, such as clearer behavioural modifications to food and heterospecific odour, and cautionary behaviour in the presence of odour from a finfish predator. During simulated daylight conditions, marron displayed behaviours conducive to predation that were not present in yabbies, including less time spent in shelter and more time spent in locomotory activity. However, during specialised night-time observational studies developed during this research, these differences were not evident. This would not seem to be an unusual result, given that crayfish naturally forage at night and become more active; however, it may have important implications for future behavioural studies of crayfish, indicating a bias associated with day-time approaches. Crayfish size also played a role in behavioural modifications to water-borne odours. Larger marron displayed clearer changes in behaviour and were more responsive to heterospecific alarm odour than juveniles. Furthermore, juveniles of both species were more active than adults and sub-adults.
The expansion of the yabby population into Western Australian habitats occupied by marron has been facilitated through translocation for aquaculture, and biological characteristics of the species, some of which are typical of other invasive crayfish species including: tolerance of a variety of conditions; rapid growth; early sexual maturity; burrowing to escape drought and predation; capable of multiple spawns in a growth season; and aggressiveness. Another characteristic of invasive crayfish species also shared by yabbies, as supported by the results of this study, is high behavioural plasticity.
Although marron do not share the same level of behavioural plasticity found in yabbies, their larger body size increases their success in competitive interactions. The comparatively smaller body size of yabbies may be the major factor limiting their population expansion in the presence of marron, especially in water-bodies where shelter is a limited resource.
Marron are an important endemic species in Western Australia, but their conservation is threatened by competition and predation from exotic species. The research presented in this thesis indicates that invasive yabbies are more receptive to chemical stimuli and better equipped to respond to predation risk than marron. This information will be of benefit when considering future translocation policy in Western Australia and highlights the need for a cautious approach to species introductions.

Understanding patterns of dispersal, the movement of individuals or propagules, among populations of riverine species is imperative to their management and conservation. However, directly estimating dispersal can often be difficult. Therefore, estimates of gene flow, the movement of genes, are often used to infer dispersal among natural populations. In riverine species, gene flow is determined by species biology, riverine architecture and flow regime. While many studies investigate the role of species dispersive strategies by comparing patterns of genetic structure in different species across the same geographic range, few also attempt to investigate the role of the non-biotic influences on gene flow in a comparative manner. Instead, studies regarding landscape processes (river architecture and hydrology) are based upon observations in a single riverine environment and not compared to other catchments that may differ in riverine architecture or hydrology. This study attempts to investigate all three factors influencing gene flow and genetic diversity using a comparative approach. This is done by contrasting two species of freshwater fish in two riverine systems that differ in their hydrological and structural makeup. By comparing patterns of genetic structure for each fish species, the role of species biology (behavioural and physical adaptations) can be explored. Then, by comparing patterns of genetic structure for each species, between riverine systems that differ in their landscape processes, the role of hydrology and riverine architecture in determining genetic structure can be explored. This study employed three different genetic markers to elucidate patterns of genetic structure and genetic diversity. These were, direct sequencing and screening of the control region of the mitochondrial DNA genome, microsatellite loci and allozymes...

Invasive species are of particular concern as they have the potential to alter community structure and food web relationships within their invaded habitats. African sharptooth catfish Clarias gariepinus, a generalist predator, was introduced through an inter-basin water transfer scheme into the Great Fish and Sundays Rivers, Eastern Cape, South Africa, where it threatens the native riverine biota. This thesis assessed its impact from a trophic perspective. Patterns in catfish distribution and abundance revealed an upstream to downstream gradient that was associated with spatial distribution of most species within the mainstream, and a mainstream to tributary gradient that was associated with the spatial distribution of native minnows. The catfish was predicted to occur widely within the mainstem habitats and to decrease progressively along the mainstrem to tributary gradient with the physico-chemical environment being a good proxy for predicting both its occurrence and abundance. The results suggest the catfish proliferated within mainstem habitats where invasion resistance was possibly reduced due to alteration of flow. Population dynamics and size structuring of two native cyprinid minnows Pseudobarbus afer and Barbus anoplus, threatened by catfish, were examined within uninvaded headwater streams in relation to their proximate physical habitats. Their habitats were characterised by seasonal variation in physico-chemical conditions and a spatial variation in substrata compositions. No evidence of differences was found between seasons for density and capture probability for either species. The population size and density for P. afer was found to increase with increasing proportion of boulders. In comparison, B. anoplus population size and probability of capture increased with increasing proportion of bedrock and bank vegetation, respectively. Size structuring was explained predominantly by seasonality and habitat variables for P. afer and B. anoplus, respectively. Stable isotope ratios of carbon and nitrogen were used to compare the spatial variation in both the community-wide and catfish-specific niches and to estimate catfish prey sources from different habitats within the invaded systems. Aquatic community and catfish niches were statistically different among localities, suggesting that each locality had a distinct community-wide trophic structure. Dispersion metrics indicated no evidence of differences in the clustering among individuals, but provided evidence of differences in path trajectories for the comparisons of catfish populations that suggested dietary plasticity within different localities. Dietary studies revealed both ontogenetic shift and omnivory that suggested that catfish may exhibit less pronounced top-down effects within its invaded habitats. Manipulative experiments were used to test the response of benthic macroinvertebrates within two rivers that were differentially impacted by catfish as a presstype disturbance. Macroinvertebrates were non-responsive to catfish presence within a system where catfish had previously been established. In contrast, excluding catfish in this system indicated a response that suggested the importance of refuge within invaded habitats and the possible recovery pattern of certain macroinvertebrate taxa. By comparison, introduction of catfish within previously uninvaded localities provided evidence of direct catfish impact through elimination of conspicuous taxa. Acoustic telemetry was used to investigate catfish movement patterns within an invaded lentic habitat and provided evidence that habitat utilisation was non-random. The shallow and structured river mouth habitat, which was most utilised, was probably the most ideal for its breeding and feeding. This inferred potential overlap with native species and suggested the risk of predation and competitive interference. Catfish also exhibited both nocturnal and diurnal activity patterns that were probably related to feeding.

To contribute to the understanding of the invasion biology of common carp Cyprinus carpio in southern Africa, this thesis investigated the life history, relative abundance, long-term population demographics and trophic niche utilisations of non-native common carp C. carpio in relation to two endemic cyprinids, Orange River mudfish Labeo capensis and smallmouth yellowfish Labeobarbus aeneus in South Africa‟s largest impoundment, Lake Gariep. The growth zone deposition rates in astericus otoliths of the three species were validated as biannual for C. carpio and as annual for L. capensis and L. aeneus, which allowed for reliable estimation of lengths-at-age upon which growth, age-at-maturity and mortality rates could be estimated. Cyprinus carpio exhibited fast growth, matured relatively early at two years of age and attained a maximum age of seven years. Labeo capensis grew significantly slower, but attained older ages of up to 12 years. Females showed notably delayed maturation at approximately six years of age. The life history parameter estimates for L. aeneus were similar to those of L. capensis. These species-specific life history characteristics contributed to a substantially higher population growth potential of C. carpio compared to L. capensis and L. aeneus. Delta-lognormal and delta-gamma Generalized Linear Models (GLMs) were used to analyse patterns of relative abundance of L. capensis, L. aeneus and C. carpio. The application of these GLMs was necessary to account for large proportions of zeros and strong skewness in the catch-per-unit-effort (CPUE) from experimental gillnet and fisheries-dependent angler surveys. Confidence intervals around predicted abundance indices were obtained through the development of a generalised parametric bootstrap procedure. The resulting standardised abundance indices were coupled with results from analysis of stable isotope ratios of fish tissues and potential food resources and revealed that C. carpio was mainly confined to soft-bottom habitats, where it predominantly foraged on benthic invertebrates. Labeo capensis was abundant in a wide range of benthic habitats and was consumed basal food resources such as detritus. Labeobarbus aeneus was found to feed mostly on pelagic zooplankton. There were no significant interspecific differences in trophic niche space, suggesting limited resource competition among the three species. Standardised historical and contemporary gillnet CPUE data indicated slow population growth rates of L. capensis and L. aeneus during the first ten years postimpoundment, but showed high biomass levels some four decades after impoundment. These results could be corroborated by stochastic age-structured production model (ASPM) simulations. In contrast to the two endemic species, the gillnet CPUE of C. carpio showed a clear „boom and bust‟ pattern, which, based on ASPM simulations, could be best explained by increased food availability during the first five years postimpoundment, followed by suboptimal conditions thereafter. Together, these results provided evidence that the establishment of the C. carpio population did not prevent the slow but successful long-term establishment of the two large endemic cyprinids. Both endemic fishes revealed specialised feeding within the impoundment.

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

A extrema sensibilidade ecológica e o carácter de bem público, da maioria dos recursos aquícolas, torna-os altamente vulneráveis. Portugal e um país com um vastíssimo património aquícola, cerca de 150 000 ha de massas de água superficiais povoadas por mais de 40 espécies piscícolas, algumas de elevado valor conservacionista e que contribuem para a manutenção da biodiversidade a nível mundial (MADRP, 2003). Neste contexto, o trabalho a desenvolver e parte integrante do projeto “GAPS - Gestão Ativa e Participada do Sitio de Monfurado “_ Numa primeira fase pretende-se fazer a inventariação das espécies de ictiofauna existentes no Sitio de Monfurado para, posteriormente, elaborar um plano de gestão dos recursos piscícolas aí presentes. Assim sendo, os principais objetivos do trabalho foram: - estudar e cartografar a distribuição das espécies ictíicas existentes no Sitio de Monfurado; - cartografar os principais obstáculos à migração da ictiofauna dulciaquícola; - propor medidas de gestão quer para as espécies autóctones, quer para as espécies exóticas, presentes na maioria das albufeiras. /ABSTRACT - Most of the aquatic resources are ecologically sensitive, this together with being a public commodity, make them highly vulnerable. Portugal has a wide patrimony of superficial water bodies, about 150 000 hectares, in which live more than 40 species of fish, some of which are highly valuable in terms of nature conservation. This thesis is part of a large project entitled “GAPS - Gestão Activa e Participada do Sitio de Monfurado”. The first phase consisted in making an inventory of the fish species existing in the Monfurado Site and, aftewards elaborate a management plan for the fishing resources. Thus, the main objectives of this work were: - study and cartograph ichthyologic species that occur in the Monfurado Site; - cartograph the main obstacles to fresh water ichthyofauna migration; - propose management measures for fish species existing in the Monfurado Site.

La biodiversité est un concept à multiples facettes qui comprend trois composantes principales, à savoir la diversité taxonomique, phylogénétique et fonctionnelle. Les études biogéographiques ont jusqu'à présent accordé plus d'attention aux deux premières facettes tandis que les déterminants de la diversité fonctionnelle et ses changements sous l'effet de l'anthropisation restent largement inconnus à l'échelle du globe. Ces lacunes sont particulièrement importantes pour les poissons d'eau douce, car ils représentent non seulement un quart des vertébrés et soutiennent le fonctionnement et la stabilité des écosystèmes, mais sont également l'un des groupes de vertébrés les plus menacés au monde. Ainsi, l'objectif de cette thèse est d'améliorer la compréhension de la diversité fonctionnelle des poissons d'eau douce du globe et de combler le fossé entre les facettes taxonomiques, fonctionnelles et phylogénétiques pour évaluer les impacts des activités humaines sur la biodiversité des poissons d'eau douce. Dans ce but, nous avons d'abord construit une base de données de traits décrivant la morphologie de 10 600 espèces présentes dans plus de 2 400 bassins fluviaux dans les six royaumes terrestres. Nous avons d'abord testé les distributions des traits morphologiques des poissons dans chaque zone biogéographique Nous avons montré que les traits morphologiques des poissons sont i) très variés à travers le globe et ii) que la distribution de ces traits est diffère entre zones biogéographiques. Cependant, les espèces morphologiquement extrêmes occupent la plus grande partie de l'espace morphologique dans toutes les zones biogéographiques. De plus, en utilisant une approche multi-traits à l'échelle du bassin versant, nous avons constaté que la diversité fonctionnelle historique a été façonnée par des variables liées à l'habitat, à l'énergie et à l'histoire. Nous avons également démontré que la morphologie diffère entre les espèces qui n'ont jamais été introduites et celles qui ont été introduites et celles qui se sont même établies. Enfin, nous avons réalisé une approche holistique en proposant un nouvel indice cumulatif combinant les changements dans les six principales facettes de la biodiversité pour évaluer les impacts des activités humaines sur la biodiversité des poissons. Nous avons constaté que les activités humaines ont considérablement affecté la biodiversité des poissons dans plus de la moitié des fleuves mondiaux (52,8%, 1 297 bassins versants). Parmi ces cours d'eau, les zones tempérées sont les plus affectées par les changements de biodiversité, et les changements de biodiversité sont principalement dus à des altérations de la connectivité de l'eau et à l'introduction d'espèces non indigènes. Ce travail a souligné le potentiel des caractéristiques morphologiques dans l'étude de la diversité fonctionnelle mondiale des poissons d'eau douce, et le indice de changement de la biodiversité à multiples facettes donnera ici ouvre de nouvelles implications pour la conservation de la biodiversité
Biodiversity is a multifaceted concept that includes three main components, namely taxonomic, phylogenetic and functional diversity. Biogeographical studies have paid more attention to the first two facets while the patterns and drivers of functional diversity and their changes because of global change remains largely unknown at the global scale. These knowledge gaps are especially large for freshwater fishes, because they not only account for a quarter of vertebrates and support the functioning and stability of ecosystems, but are also one the most threatened vertebrates groups in the world. Thus this thesis aims to improve the understanding of the functional diversity of global freshwater fishes and bridge the gap between taxonomic, functional and phylogenetic facets to evaluate the impacts of human activities on the multifaceted biodiversity of global fishes. Towards this aim, we first built a trait database describing the morphology of 10 600 species occurring in over 2 400 river basins all over the six terrestrial realms. First, we assessed the distributions of the morphological traits within the fauna of each realm. We revealed that fish morphological traits are different between realms and that morphologically extreme species are distributed in all realms. Second, using a multi-traits approach at the basin scale we found that the historical functional diversities have been shaped by habitat, energy and history-related variables. Third, we demonstrated that morphology differs between species that have never been introduced species and those that were introduced and those that were even established. Last, using a novel cumulative index combining changes in six facets of biodiversity we found that human activities have markedly affected fish biodiversity in more than half of the world river (52.8%, 1 297 rivers). Those biodiversity changes were primarily due to alterations of water connectivity and introductions of non-native species. This work underlined the potential of morphological features in the study of global freshwater fish functional diversity, and the combination of functional phylogenetic and taxonomic features in a novel multifaceted biodiversity change index will constitute a useful tool for biological conservation

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.

碩士
國立臺中教育大學
美術學系碩士在職專班
104
Visual arts education nowadays theoretically provides students an opportunity to discover their surroundings through the acquisition of discovery, creation, aesthetic standards, and speculation, culture understanding skills in class. After the examination of a great deal of relevant references on natural awareness and visual arts education documents, “Native freshwater fish course integrated into visual arts education in higher grade”———as the research topic, aims to discuss the integration of visual arts course infused with natural awareness points of view and serve to examine its process and effectiveness of teaching. The research, taking students of higher grade as the objects, has formed a framework based on Flow Learning, created by Joseph Cornell who has moreover indicated “Five principles of instruction” and “Four steps to experience”. The goal is to lead students to undertake art creations after the implementation of natural awareness, in hope of inspiring their aesthetic standards and creative thinking competence, eventually to seek the important implications of visual arts education infused with natural awareness. Here are the four outcomes of this research: 1.The enhancement of knowledge and recognition over school natural surroundings. 2.Students’ interest in art creation would be successfully maximized with the topic “native freshwater fish”¬¬¬¬¬———visual arts course infused with natural awareness. 3.The satisfaction with the teaching orientation from students. 4.The compassion and the enjoyment towards Mother Nature would be wildly incited.

Characterization of smallmouth bass (Micropterus dolomieu) interaction with native species assemblages, especially salmonids, in lakes throughout BC is prerequisite to identification of high-risk systems warranting on-going monitoring. Therefore this project addresses the following issues: How does smallmouth bass (SMB) trophic profile overlap with native species and does it vary across time and space? Schoener’s index of dietary overlap was not significant between SMB and rainbow trout (Oncorhynchus mykiss; α=0.406, 0.257), or cutthroat trout (Oncorhynchus clarkia; α=0.145, 0.29). Prey fish levels (Ei =35.4%) and the total energetic density (14.91±4.74J/g) of the cutthroat trout diet from Weston Lake (SMB free) were significantly higher compared to the diet of cutthroat trout from Cusheon Lake (Ei =3.3% and 7.69±1.93J/g) where non-native SMB have been introduced. Within the Vancouver Island study lakes, gut-content analysis revealed available signal crayfish serve as an important prey resource in the SMB diet (Ei =34%). What capacity do SMB have to take advantage of seasonal pulses of forage? SMB displayed the ability to rapidly (within 24hrs.) alter their diet and consumption levels (4.7 times higher) to maximize on pulses of rainbow trout fry following a stocking event. SMB did not spatially overlap with spring peaks in salmonid fry runs in the Okanagan lakes, as water temperature remained around the 10°C threshold when SMB are not yet active. Kokanee (Oncorhynchus nerka) fry did however make up Ei =83% of the yellow perch (Perca flavescens) diet. SMB are thriving in locations suspected to be on the limit for their environmental suitability through increased size at age for SMB in the Cariboo region in order to adapt to a longer (by 62 days) winter starvation period. SMB are a generalist predator able to adapt and thrive in very different systems; high vs. low productivity, few or many fish species, crayfish or no crayfish. The likely impacts of this in BC could include shifts in the diet of other fish species and increased costs associated with only stocking larger catchable sized trout in lakes containing non-native SMB. Policy recommendations based on our findings are that SMB introductions into systems that have rainbow/cutthroat trout are likely to cause the highest impacts on our native fisheries in BC if the systems are; highly productive, contain a high diversity of small bodied fish and invertebrate species, lack signal crayfish and large lakes with predominant littoral zones and complex shorelines.
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mbeck@uvic.ca