The introduction, spread and concomitant impacts of non-native species are a global problem. Fish are among the most widely introduced vertebrate groups, with their impacts affecting multiple levels of organisation- from individuals, populations and communities, to entire ecosystems. In South Africa, the largest perceived threat to range-restricted endemic headwater stream fishes is said to be invasion by non-native fishes, however, as is the case elsewhere, invasive impacts are often a case of risk perception rather than actual risk analysis. Two range-restricted headwater species, the Eastern Cape redfin Pseudobarbus afer and the Border barb Barbus trevelyani are redlisted by the International Union for the Conservation of Nature (IUCN) as ‘Endangered’, primarily due to invasion by non-native fishes. To investigate invasions in South Africa, and provide a quantitative estimate of the impact of non-native fishes on the two imperilled endemics, P. afer and B. trevelyani, the overall aims of this thesis were to: (A) Provide a literature review on non-native fish invasions in South Africa; (B) Using two case studies on the headwaters of the perennial Keiskamma and episodic Swartkops River systems, investigate the naturalisation-invasion continuum to provide a holistic view of the invasion process in these variable environments. The specific thesis objectives were: (1) Reviewing current knowledge of invasive impacts of non-native fishes in South Africa; (2) Investigating invasibility of headwater stream environments by non-native fishes; (3) Determining the establishment success of non-native fishes, (4) Assessing the spatial and temporal impacts of invasion; (5) Understanding mechanisms responsible for non-native fish impacts; (6) Investigating the threat of non-native fish invasion on the genetic diversity of two the two headwater fishes, P. afer and B. trevelyani. Results from the literature review of fish invasions (Chapter 1) showed that South Africa has a long history of non-native fish introductions, spanning two and a half centuries. Currently, 55 species have been introduced or translocated. Many of these introduced species have become fully invasive (36%). Their impacts also span multiple levels of biological organisation. There was a general paucity of studies on fish invasions (38 studies), however, of those conducted, reviewed studies placed emphases on invasive impacts (25 studies) and the transport, introduction, establishment and spread stages of the invasion process were largely ignored. The two study systems, the Swartkops and Keiskamma Rivers, were heavily invaded and numbers of introduced species surpassed that of natives (Chapter 2, 3 and 5). Headwater streams had varying invasibility and a number of non-native species were successfully established (Chapter 2, 3, 5 and 6). The remainder of the invasions were casual incursions into headwater streams from source populations in mainstream and impoundment environments which were invasion hotspots. Irrespective of establishment, four predatory invaders (largemouth bass Micropterus salmoides, smallmouth bass M. dolomieu, brown trout Salmo trutta and rainbow trout Oncorhynchus mykiss) impacted heavily on native fish communities (Chapter 3, 4 and 5). Two broad types of invasion were documented, top down invasion by non-native O. mykiss and S. trutta and upstream invasion by M. salmoides and M. dolomieu (Chapter 3 and 5). Their impacts included changes in community structure, extirpation from invaded stream reaches resulting in contracted distribution, and isolation and fragmentation of native fish populations. The impacts of non-native predatory fishes were particularly acute for P. afer and B. trevelyani. Where non-native predatory fish occurred, P. afer and B. trevelyani had been extirpated (Chapter 3 and 5). As a result both native species exhibited contracted distributions (>20% habitat loss due to invasion). Upstream invasion by centrarchids isolated and fragmented P. afer populations into headwater refugia, while top down invasion by salmonids excluded B. trevelyani from invaded, more pristine stream reaches, by forcing the species into degraded unsuitable lower stream reaches. Predation also disrupted population processes such as adult dispersal for P. afer, and centrarchid-invaded zones acted as demographic sinks, where adults dispersing through invaded reaches were rapidly depleted. While the Mandela lineage of P. afer exhibited little within or between drainage genetic structuring, B. trevelyani was >4% divergent between drainages, and up to 2% divergent between streams within the Keiskamma River system (Chapter 7). The distribution of genetic diversity for B. trevelyani also indicated that the loss of diversity was imminent without immediate conservation interventions. This thesis has provided conclusive evidence that native fishes are vulnerable to invasion and that non-native predatory fishes have significant impacts on native fishes in Eastern Cape headwater streams. If management and conservation measures are implemented, the unwanted introduction and spread of non-native fishes may be restricted, allowing native fishes opportunities for recovery.

Despite more than a century of introductions, fish invasions are poorly understood in South Africa. This thesis aims to: (1) provide baseline information on the fish fauna in five inland water bodies (four dams: Theewaterskloof, Clanwilliam, Quaggaskloof, and Voelvlei and a natural lake, Groenvlei) in the Western Cape; (2) determine which species were established and provide a baseline of abundance and size structure for monitoring and, (3) make preliminary recommendations for a fishery. First, criteria for determining establishment were developed by undertaking a full biological assessment of bluegill Lepomis macrochirus, a data-poor species in South Africa. This included the assessment of growth rate using validated estimates of age derived from otoliths in two dams (Clanwilliam Dam: Lt=335.9(1−eo.113(t+1.06)); Groenvlei: Lt=287.2(1-e−0.171(t+0.54)). Length at 50% maturity was similar for males (146 mmFL) and females (147 mmFL). Length frequency analysis combined with data on the age and growth and reproduction demonstrated that established populations of bluegill contained several age cohorts as well as mature and juvenile fishes. A meta-analysis was conducted to: (1) compile a list of initial stocking dates for all alien fishes in each waterbody and (2) use angler tournament data to assess for additional species and persistence over time. Data from the meta-analysis was combined with ichthyological survey data to determine establishment success. These data demonstrated that nine non-native species had established in the five water bodies. Clanwilliam Dam had the largest number (7) of non-native species established, Groenvlei (5) and Theewaterskloof, Brandvlei and Voelvlei the lowest with four species. The state of invasion of each species in the province showed that all nine species are categorised as invasive. This information on establishment was then integrated into a framework for rapidly determining what type of fishery would be most suitable for the 5 waterbodies. Potential yield was estimated using morphoedaphic models, were 260 t/yr for Theewaterskloof Dam, 93 t/yr for Voelvlei, 81 t/yr for Brandvlei, 59 t/yr for Groenvlei and 55 t/yr for Groenvlei. The CPUE for Groenvlei was the highest in gill nets with 1.32 ± 1.94 kg/h, then Voelvlei 1.05 ± 1.34 kg/h followed by Brandvlei (0.84 ± 1.48 kg/h), Clanwilliam (0.71 ± 1.55 kg/h) and lastly Theewaterskloof (0.36 ± 0.41 kg/h). Only Theewaterskloof could produce in excess of 100 t/yr but less than 400 t/yr of fish making it suitable for a small scale fishery. The CPUE values of Theewaterskloof were the lowest and a gill net fishery on this water body may not produce sufficient fish for the fishery. All water bodies had a high recreational angling usage, the opening of a small scale fishery could be detrimental to this industry. Subsistence and recreational anglers should be promoted with the possibility of a long line industry targeting Clarias gariepinus.

The development of a fisheries and wildlife indicator system is described. The system is intended to serve as a planning and policymaking aid for state fisheries and wildlife agencies and to enhance communications between state agencies and the public. The conceptual basis for the indicator system derives from the field of social indicators research and rests on the premise that explicit decisionmaking methods are more desirable than intuition and subjective methods. Four major steps were involved in developing the fisheries and wildlife indicator system. The first step was assessing the current availability of resource information and involved analyzing state fisheries and wildlife agency annual reports. Administrative information was emphasized in reports over fisheries and wildlife resources and their use. States rarely reported trend statistics that allow comparisons over time to be made. Reports contained a mixture of quantitative and qualitative information, but contained few tables and graphs compared to the amount of text. Assessing the type, quality, and quantity of performance information currently available laid the base for subsequent work on the indicator system. The second step was developing a comprehensive classification framework representing all aspects of the fisheries and wildlife resource. The framework, a 16-cell matrix including the resource categories of People, Populations, Habitat, and Administration, and the resource components of Inputs, Processes, Outputs, and Impacts, contained 82 separate resource characteristics representing the universe of concerns and responsibilities faced in state-level fisheries and wildlife management. The third step was identifying indicators representative of each characteristic in the framework. Through an extensive analysis of fisheries and wildlife literature, agency documents, and social assessment literature, 377 indicators were identified. Based on appropriateness and availability of each indicator, 242 indicators were recommended for monitoring by state fisheries and wildlife agencies. The last step in the process was describing the use of the fisheries and wildlife indicator system, how the system can fit into an agency's administrative structure and planning programs, and how its use may affect the future of fisheries and wildlife management. / Ph. D. / incomplete_metadata

Until the 1990s, salmon had been extinct from the Umatilla River for over 70 years. The struggle to bring salmon back to this river is a compelling story that exemplifies some of the new relationships in Columbia River Basin salmon management. The Umatilla River and the disappearance of its salmon was a local issue. Irrigation interests had used the river so thoroughly it ceased to flow during the late summer and fall months-precisely when salmon needed it for migration. The Confederated Tribes of the Umatilla Indian Reservation saw decided that they would change that: they would figure out a way to put both salmon and water back into the river. This thesis examines this process. First, it contextualizes the Umatilla River within the Columbia River Basin and Columbia Basin salmon management, and shows how a local salmon issue became a regional salmon issue. It then discusses the triangle of relationships that Indians, salmon, and hatcheries have come to form. Chapter III discusses the formation of the unique Umatilla Fish Restoration Program, which reintroduced fish into the river, and was paid for by the Bonneville Power Administration (BPA), as per the Northwest Power Act. Key elements within BPA's Fish and Wildlife Division resisted complying with the directives of the Northwest Power Planning Council to pay for the Program, setting the Program back years. I argue that this comes from two clashing ways of seeing the River: "cost-benefit analysis" versus "least cost." Chapter IV looks at the new partnerships formed in the Umatilla River Basin by the Tribes and irrigation districts in order to encourage the U.S. Bureau of Reclamation to construct a water delivery system that would satisfy irrigators while allowing most of the Umatilla to flow freely. The last Chapter suggests that these new and somewhat ironic partnerships between federal and state governments, private irrigators and landowners, nongovernmental organizations, and Indian tribes are key to restoring ecosystems in the Columbia River Basin. It further argues that without tribal nations playing an active role and exerting their treaty rights, restoring rivers like the Umatilla is impossible.