Social judgment analysis was used to define design criteria for urban fisheries in small ponds and natural waterfronts. The analysis involved (1) compiling a team of expert judges, (2) creating a series of hypothetical cases for ponds and waterfronts, (3) having the experts judge the quality of the cases, and (4) creating multiple regression equations that described their individual and combined judgments. Fifty-nine urban fisheries managers were identified from a survey of public fisheries agencies and private organizations. Twenty-eight experts were selected based on amount and types of experience and geographic distribution. Content analysis of the urban fisheries literature was used to identify potentially important design elements. Sixteen experts each judged the quality of 40 small pond and 40 waterfront fisheries based on (1) percentage of the management program devoted to education, (2) percentage of the program planned locally, (3) percentage of the program funded locally, (4) accessibility of the fishery, (5) percentage of the shoreline available for fishing, (6) stocking rate, (7) overall water quality, and (8) shoreline distance between fish attraction structures. Urban pond fisheries experts identified two general management approaches to urban pond fisheries. Group 1 managers indicated a focused policy based primarily on stocking, shoreline available for fishing, and accessibility of the fishery. Group 2 managers indicated a broader policy less directed at any particular element, but with emphasis on stocking, water quality, education, and available shoreline. Both groups indicated that local planning, local funding, and attraction structures were relatively unimportant in their decisions concerning fishery quality. Waterfront experts favored an even broader management policy with a greater distribution of relative importance across all the elements. However, the relatively small number of waterfront experts included in the policy development and the broad approach indicates the variability of waterfronts. This variability made the development of management generalizations for urban waterfront fisheries difficult. / Master of Science

Molecular genetic markers can be used to assess genetic diversity, assign parentage, quantify inbreeding, and demonstrate structuring of populations across a system. Striped Bass Morone saxatilis, and Walleye Sander vitreus, are widely sought gamefishes in the Commonwealth of Virginia. Striped Bass along the Atlantic Coast and within the Roanoke River drainage exhibit low genetic variation. Screening 12 microsatellite DNA markers across the range to define population genetic structure, I found that anadromous populations in the Southeast and the Chesapeake Bay were differentiated from landlocked populations in the Roanoke River basin, with an average FST of 0.066. Range-wide, Striped Bass are differentiated between the landlocked and anadromous populations, which need to be managed separately. Within stocked populations in the Roanoke River basin, there have been impacts stemming from small numbers of broodstock propagated, and inter-individual relatedness is ~20% within stocked reservoirs. Walleye across the eastern native range were screened to better understand evolutionary history and to identify native marker alleles for the upper New River population. Population genetic variation at eight microsatellite loci showed differentiated stocks in Alabama, Mississippi River, Eastern Highlands (Tennessee, New, and Ohio Rivers), and the Great Lakes drainages. All estimates of effective numbers of breeding individuals were under 25, and all populations within all watersheds had ~15-20% inter-individual relatedness, likely effects of both natural demographic processes and stocking. The extent of Eastern Highlands Walleye includes both the Ohio and Tennessee basins. Although I did not identify new marker alleles for native New River Walleye, I determined that marker-assisted selection has increased the frequencies of existing marker alleles for the native stock. Application of the results of this project will contribute to better fisheries management for both of these important species. / Master of Science / Population genetics have proven useful for defining the most appropriate units for conservational management across a variety of species. Molecular genetic markers can be used to assess genetic diversity, assign parentage, quantify inbreeding, and demonstrate structuring of populations across a system. Striped Bass Morone saxatilis and Walleye Sander vitreus are both widely sought gamefishes in the Commonwealth of Virginia. I applied population genetic approaches to recognize genetically distinct groups of populations and to recommend genetically cognizant management practices. Striped Bass across the Atlantic Coast and in the Roanoke River drainage exhibit low genetic variation. After screening variation at 12 DNA markers, I found that Striped Bass are differentiated between landlocked and migratory populations, which need to be managed separately. Within stocked populations in the Roanoke River basin, there have been impacts stemming from propagation of small numbers of broodstock, and propagation and stocking practices will need to be changed to reduce apparent inbreeding depression. Walleye populations across the eastern native range were screened to better understand evolutionary history and to seek new marker alleles for the native upper New River population. After screening genetic variation at eight DNA marker loci, I identified four evolutionarily distinct stocks of Walleye across eastern North America. Although I did not identify new marker alleles for native upper New River native Walleye, I showed that marker-assisted selection has increased the frequencies of existing marker alleles over the past twenty years. The results of this project can contribute to better fishery management strategies for both of these important gamefish species.

Approximately 24 alien fish species, equivalent to 9 percent of all South African freshwater fish species, were introduced and established into South African waters during the 19th and 20th Centuries (Skelton, 2001). Of the 24 species introduced, the Rainbow trout and the Brown trout have over time become South Africa's most widely spread and used freshwater fish species (Bainbridge, Alletson, Davies, Lax and Mills, 2005). The National Environmental Management: Biodiversity Act, no.10 of 2004 has, however, cast considerable doubt on the future of trout as a food source and a recreational fishing resource in South Africa. More specifically, Section 64 of the Act has the following aims: “(a) to prevent the unauthorized introduction and spread of alien species and invasive species to ecosystems and habitats where they do not naturally occur; (b) to manage and control alien species and invasive species to prevent or minimize harm to the environment and to biodiversity in particular; and (c) to eradicate alien species and invasive species from ecosystems and habitats where they may harm such ecosystems or habitats.” The uncertainty surrounding the future of trout in South Africa is mainly underpinned by aim (c) of Section 64 of the Act. Regarding the eradication of trout and in keeping with aim (c) of Section 64 of the Act, three remarks can be made. First, there exists a paucity of published studies which offer validated proof of the impacts which may be ascribed entirely to the introduction of alien trout in South Africa, since no pre-stocking assessments were conducted (Bainbridge et al., 2005). Second, the elimination of trout is feasible in a few limited closed ecosystems, such as small dams, but is highly impractical and untenable from an environmental and cost perspective where open and established river systems are concerned (Bainbridge et al., x 2005). More specifically, there are no efficient or adequate eradication measures which may be used in wide-ranging open ecosystems, which selectively target alien fish species. Moreover, most, if not all, measures have the potential to cause considerable adverse impacts on indigenous aquafaunal species. Finally, the elimination of trout could undermine the tourism appeal of many upper catchment areas in South Africa. The trout fishing industry is well established and is a source of local and foreign income, as well as a job creator in the South African economy (Bainbridge et al., 2005; Hlatswako, 2000; Rogerson, 2002). In particular, the industry provides a two-tier service: first, in food production at the subsistence as well as commercial levels, and second, as an angling resource. Recreational angling, including fly-fishing for trout, is one of the fastest growing tourism attractions in South Africa. Furthermore, the trout fishing industry is sustained and underpinned by a considerable infrastructure consisting of tackle manufacturers and retailers, tourist operators, professional guides, hotels, lodges and B&Bs. The economic case for the trout fishing industry in South Africa has, however, not been convincingly made. The economic benefit provided by trout and trout fly-fishing is priced directly in the market place by expenditures made by fly-fishers, and indirectly in property values, which provide access to fly-fishing opportunities. The benefit of trout and trout fly-fishing can also be valued through non-market valuation techniques. Non-market valuation is used to calculate values for items that are not traded in markets, such as environmental services. There are several non-market valuation methods available to the researcher, namely those based on revealed preference and those based on stated preference. The former includes the hedonic pricing method and the travel cost method, while the latter includes the contingent valuation method and the choice modelling method. Of the available non-market valuation techniques, the travel cost method is the most suitable method for determining the value of trout and the trout fishing industry because travel cost is often the main expenditure incurred. xi The aim of this study is threefold: first, to value the economic contribution of trout and trout fly-fishing to the Rhodes region, North Eastern Cape; second, to determine the willingness-to-pay for a project that entails the rehabilitation and maintenance of trout streams and rivers in and around Rhodes village so as to increase their trout carrying capacity by 10 percent; third, to determine the willingness-to-pay for a project aimed at eradicating trout from streams and rivers in and around Rhodes village so as to prevent trout from harming the indigenous yellowfish habitat. The first aim was achieved by applying the travel cost method, whereas the second and third aims were achieved by applying the contingent valuation method. The study aimed to provide policy makers with information regarding the value of trout fishing in the Rhodes region, so as to create an awareness of the economic trade-offs associated with alien fish eradication. Through the application of the travel cost method, the consumer surplus per trout fly-fishermen was estimated to be R19 677.69, while the total consumer surplus was estimated to be R13 774 384.40. The median willingness-to-pay for a project to rehabilitate trout habitat was estimated to be R248.95, while the total willingness-to-pay amounted to R199 462.20. The median willingness-to-pay for a project to eradicate alien trout from the Rhodes region rivers and streams was estimated to be R41.18, while the total willingness-to-pay amounted to R28 829.36. This study concludes that trout and trout fly-fishing make a valuable economic contribution to the Rhodes region. The extent of the economic benefit provided by trout and trout fly-fishing services in the Rhodes region should be carefully considered in any stream management project.

The groundfish trawl fishery operating off the coasts of Oregon and Washington 1985-1987 caught six major assemblages of species which could be treated as units in developing mixed-species management plans. Eighty-one percent of the tows observed on commercial vessels were consistently placed in one of the assemblage designations using three multivariate techniques. Two of the assemblages were dominated by a single species, pink shrimp (Pandalus jordani) or widow rockfish (Sebastes entomelas). The other assemblages identified were: a deepwater rockfish assemblage, a deepwater Dover sole assemblage, a nearshore mixed-species assemblage, and a bottom rockfish assemblage. The assemblage designations of the consistently placed tows were predicted with an estimated 85% average accuracy using discriminant functions based on the gear used and bottom depth fished. Fishermen had different targets (intended catch) for each assemblage caught. The mixed-species assemblages had several targets, representing at least some of the dominant species in the assemblage. Targeting and discarding information indicated that fishermen did not always intend to catch the species together; there were unintentional or unavoidable catches of all the major species except for shrimp in the shrimp assemblage. Discarding occurred in all the assemblages, primarily due to unmarketable species or fish that were too small to market. Monitoring the assemblages over time could be accomplished by using the defined strategies with logbook data, particularly if the large and small rockfish categories were used to consistently separate shelf and deepwater rockfish. The defined strategies could not effectively predict the research cruise assemblages or catches; research data do not accurately describe commercial catches. / Graduation date: 1994

published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

In fisheries, advice for the management of fish populations is based upon management quantities that are estimated by stock assessment models. Fisheries stock assessment is a process in which data collected from a fish population are used to generate a model which enables the effects of fishing on a stock to be quantified. This study determined the effects of various data sources, assumptions, error scenarios and sample sizes on the accuracy with which the age-structured production model and the Schaefer model (assessment models) were able to estimate key management quantities for a fish resource similar to the Cape hakes (Merluccius capensis and M. paradoxus). An age-structured production model was used as the operating model to simulate hypothetical fish resource population dynamics for which management quantities could be determined by the assessment models. Different stocks were simulated with various harvest rate histories. These harvest rates produced Downhill trip data, where harvest rates increase over time until the resource is close to collapse, and Good contrast data, where the harvest rate increases over time until the resource is at less than half of it’s exploitable biomass, and then it decreases allowing the resource to rebuild. The accuracy of the assessment models were determined when data were drawn from the operating model with various combinations of error. The age-structured production model was more accurate at estimating maximum sustainable yield, maximum sustainable yield level and the maximum sustainable yield ratio. The Schaefer model gave more accurate estimates of Depletion and Total Allowable Catch. While the assessment models were able to estimate management quantities using Downhill trip data, the estimates improved significantly when the models were tuned with Good contrast data. When autocorrelation in the spawner-recruit curve was not accounted for by the deterministic assessment model, inaccuracy in parameter estimates were high. The assessment model management quantities were not greatly affected by multinomial ageing error in the catch-at-age matrices at a sample size of 5000 otoliths. Assessment model estimates were closer to their true values when log-normal error were assumed in the catch-at-age matrix, even when the true underlying error were multinomial. However, the multinomial had smaller coefficients of variation at all sample sizes, between 1000 and 10000, of otoliths aged. It was recommended that the assessment model is chosen based on the management quantity of interest. When the underlying error is multinomial, the weighted log-normal likelihood function should be used in the catch-at-age matrix to obtain accurate parameter estimates. However, the multinomial likelihood should be used to minimise the coefficient of variation. Investigation into correcting for autocorrelation in the stock-recruitment relationship should be carried out, as it had a large effect on the accuracy of management quantities.

No description available.

Thesis (MPhilAgric)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: Not only have non-trade barriers been applied in Europe and the US to agricultural products from developing countries, but protective policy is also likely to continue. Owing to the omission of fish from the discussions in the final round of agreement at Uruguay, where tariffs were significantly reduced for other agricultural products, the fish industry has not had any non tarriff barier relief in recent years. The failure of the November 1999 World Trade Organisation Meeting at Seattle to reach any agreement, has again shattered hopes of international relief for fishery products. The main assumption underlying the study was that the production of fish in Tanzania could improve significantly if the HACCP (Hazard Analysis Critical Control Points) principles were applied rigorously. It was believed that neither the prerequisite programmes, nor HACCP principles were probably applied as stringently as international standards require. The aim of the study was to review the literature on HACCP, programmes that are prerequisite for HACCP and factors that_ determine competitiveness in business and to examine the Tanzanian Nile perch industry against this background. The overall goal was to determine how the industry could become more internationally competitive. This was achieved by comparing the socio-economic reality of Tanzania with factors that are considered in the literature to affect competitiveness in general and in the fish industry specifically. To achieve the first of these aims, Tanzania's socioeconomic position as a developing country was examined. To achieve the latter, the commitment of fish processing factories to the application of HACCP principles and their compliance with prerequisite programmes were evaluated in a field study. The literature study confirms that HACCP has received international recognition in the fish industry as a factor to prevent hazards and gain competitiveness in the global fish market. However, conditions in Tanzania were shown to be insufficient to support the fisheries sector in attempting to gain such a competitive advantage. Although, Tanzania has the comparative advantage of a fishery resource base, a favourable trade policy and foreign technology and management, the macro-factors that include the infrastructure, human resource capital, foreign policy environment and the supporting industries are not supportive. For the time being, therefore, improvement can only come from the government and from the industry itself. There are several factors to which the government needs to pay attention in order to support this industry - and others - in achieving international success. These include the provision of infrastructure and facilities, the improvement of the transportation network, technological capabilities, human resource capital and the provision of safe water and electric power. However, the fish industry cannot rely on the government alone. The improvement of their product is also dependent on their own efforts. According to the findings of this study, the industry needs to comply with the basic sanitation factors and provide the necessary training to the employees and fish suppliers. Having examined the situation more closely, the assumption is proved to be correct. The fish industry in Tanzania does indeed appear to have the potential to become internationally competitive. Such success, however, will be heavily dependent on cooperation between the government and the industry / AFRIKAANSE OPSOMMING: Handelsbeperkinge op landbouproduckte vanaf ontwinkkelende in Europa en die Verenigde State toegepas. Daarbenewens sal beskermende beleidsriglyne waarskynlik in stand gehou word. Bespreking van sake met betrekking to vissery is nie by die finale rondte van ooreenstemming te Uruquay, waar tariewe vir ander landbouproduckte betekenisvol verlaag is, ingesluit nie, en daardeur is daar gedurende die laaste aantal jare geen belastingverligting vir die visindustrie gebied nie. By die World Trase Organisation se vergadering om internasionale verligting vir visproducte te verkry, weereens beskaam. Die hoofveronderstelling wat hierdie studie ondersteun, is dat visproduksie III Tanzanie betekenisvol verbeter kan word indien die can HACCP (Hazard Analysis Critical Control Points) streng toegepas word. Dit is veronderstel dat nóg die voorvereiste programme, nóg die HACCP-beginsels wat ten opsigte van internasionale standaarde vereis word, streng volgens voorskriftoegepas word. Die doel van die studie was om 'n oorsig van die literatuur oor HACCP, programme wat as HACCP-voorvereistes geld en faktore wat mededingendheid in die besigheidswereld bepaal, te verkry en om die Tanzaniese Nyl-baarsbedryf teen hierdie agterground te ondersoek. Die oorkoepelende doel was om vas te stel hoe die bedryf internasionaal meer mededingend kan word. Dit is gedoen deur middel van vergelyking tussen die sosio-ekonomiese werklikheid van Tanzanië en die faktore wat mededingendheid in die algemeen, volgens die literatuur, en die visbedryf in besonder, affekteer. Om die eeste van hiedie doelstellings te bereik, is die sosio-ekonomies posisie van Tanzanie as 'n ontwikkelende land ondersoek Om die tweede te bereik, is 'n veldstudie uitgevoer om die mate waartoe fabrieke wat vis verwerk daarop ingestel is om HACCP-beginsels toe te pas en hul gewilligheid om die programme wat as voorvereistes dien, na te kom, te evalueer. Die literatuurstudie het bevestig dat HACCP internasionale erkenning geniet as 'n faktor om risikO in de visbedryf uit te skakel en mededingendheid op die wereldmark vir vis te verwerf. Daar is egter bewys dat toetstande in Tanzanie ontoereikend is om die visserysektor in die verwewing van'n mededingende voorsprong te ondersteun. Alhoewel Tanzanië oor die relatiewe voordele van vissery as 'n hulpbron, gunstige handelsbeleid en buitelandse tegnologie en bestuur bestik, bied die makrofaktore soos infrastruktuur, kapitaal III die vorm van menslike hulpbronne, die buitelandse beleidsomgewing en die ondersteunende bedrywe nie genoeg ondersteuning nie. Vir die hede, kan ontwikkeling dus slegs deur die regering en die bedryf self bewekstelling word. Daar is verskeie faktore waaraan die regering aandag moet skenk om hierdie bedryf-en ander bedrywe-in die verkryging van internasionale sukses te ondersteun. Sulke faktore omvat die daarstelling van infrastruktuur en fasiliteite, die verbetering van die vervoernetwerk, tegnologiese vermoens en menslike hulpbronkapitaal, en voorsiening van onbesmette water en elektriese krag. Die visbedryf kan egter nie net op die regering steun nie. Die verbetering van die product is van die bedryf self afhanklik. Die bevindings van hierdie studie dui daarop dat die bedryf die basiese faktore betreffende sanitêre beginsels moet onderhoue en die vereiste opleiding aan diensnemers moet verskaf. By die nadere ondersoek van die situasie is die oorspronklike veronderstelling korrek bewys. Die visbedryf in Tanzanië beskik oor die potensiaal om internasionaal medengend te word. Sodanige sukses sal egter uiters afhanklik wees van samewerking tussen die regering en die bedryf.

published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

published_or_final_version / abstract / Ecology and Biodiversity / Master / Master of Philosophy