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Interactions of the South African fur seal and fisheries in the Benguela ecosystem
Bibliography: pages 168-180.
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| Other Authors: | |
| Format: | Thesis |
| Language: | English |
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Department of Biological Sciences
2016
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| _version_ | 1867613230564638720 |
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| access_status_str | Open Access |
| author | Wickens, Patricia Anne |
| author2 | Field, John G |
| author_browse | Field, John G Wickens, Patricia Anne |
| author_facet | Field, John G Wickens, Patricia Anne |
| author_sort | Wickens, Patricia Anne |
| collection | Thesis |
| description | Bibliography: pages 168-180. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/22566 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:32:50.328Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2016 |
| publishDateRange | 2016 |
| publishDateSort | 2016 |
| publisher | Department of Biological Sciences |
| publisherStr | Department of Biological Sciences |
| record_format | dspace |
| source_str | UCTD — University of Cape Town Open Access Repository |
| spelling | oai:open.uct.ac.za:11427/22566 Interactions of the South African fur seal and fisheries in the Benguela ecosystem Wickens, Patricia Anne Field, John G Shelton, Peter A Cape fur seal - Ecology Sealing - South Africa - Environmental aspects Fisheries - Environmental aspects - South Africa Bibliography: pages 168-180. This thesis adopts an holistic approach to evaluation of the "seal problem", which encompasses the operational and biological interactions between the South African fur seal and fisheries in the Benguela Ecosystem. The operational interactions are examined using a qualitative assessment, and speculative, single-species simulation models are developed to improve understanding of seal population dynamics, present options for seal management and explore seal-fishery interactions. The models show that the probability of a seal living longer than 20 years is 14%; that the population has increased at a rate of 5.1 % p.a. since the last major census in 1983; that in 1988 there were an estimated 1.5 million seals that consumed over 2 million tons of fish; that although seal population size is usually estimated by multiplying the number of pups by a factor of 4, this factor is very variable and under different culling regimes is usually greater than 4; that historically, the mean population : pup ratio is 4.55. The most effective means of reducing the population is to cull both pups and bulls (the population decrease resulting mainly from reduced pup production caused by disturbance during bull culling). Culling pups is the least effective means of population control. Culling cows alters the population sex ratio drastically and is considered undesirable. To achieve a small or negative population growth rate, more bulls and pups need to be culled than have been taken historically. Each of the fisheries is found to be subject to operational interactions with seals, this being most severe for the purse-seine fishery. The per capita consumption of fish by seals is similar under any management regime so it is not justified to adopt a particular culling strategy to reduce overall consumption. When either seal predation or fishing mortality is reduced, the model simulates an increase in fishery yield of Cape hakes. But there is inadequate understanding of hake population dynamics at present, and depending on the interactions between species, decreased predation may result in increased or decreased fishery yields. This study shows that operational interactions are a real problem and this biases the opinion of fishermen towards seals as competitors for fish resources. 2016-11-16T13:25:07Z 2016-11-16T13:25:07Z 1989 Doctoral Thesis Doctoral PhD http://hdl.handle.net/11427/22566 eng application/pdf Department of Biological Sciences Faculty of Science University of Cape Town |
| spellingShingle | Cape fur seal - Ecology Sealing - South Africa - Environmental aspects Fisheries - Environmental aspects - South Africa Wickens, Patricia Anne Interactions of the South African fur seal and fisheries in the Benguela ecosystem |
| thesis_degree_str | Doctoral |
| title | Interactions of the South African fur seal and fisheries in the Benguela ecosystem |
| title_full | Interactions of the South African fur seal and fisheries in the Benguela ecosystem |
| title_fullStr | Interactions of the South African fur seal and fisheries in the Benguela ecosystem |
| title_full_unstemmed | Interactions of the South African fur seal and fisheries in the Benguela ecosystem |
| title_short | Interactions of the South African fur seal and fisheries in the Benguela ecosystem |
| title_sort | interactions of the south african fur seal and fisheries in the benguela ecosystem |
| topic | Cape fur seal - Ecology Sealing - South Africa - Environmental aspects Fisheries - Environmental aspects - South Africa |
| url | http://hdl.handle.net/11427/22566 |
| work_keys_str_mv | AT wickenspatriciaanne interactionsofthesouthafricanfursealandfisheriesinthebenguelaecosystem |