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A quantitative bio-economic investigation of inshore fisheries
Dissertation (PhD)--University of Stellenbosch, 2001.
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| Other Authors: | |
| Format: | Thesis |
| Language: | en_ZA |
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Stellenbosch : Stellenbosch University
2012
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| _version_ | 1867613890650570752 |
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| access_status_str | Open Access |
| author | Du Toit, Elmari |
| author2 | Cruywagen, G. C. |
| author_browse | Cruywagen, G. C. Du Toit, Elmari |
| author_facet | Cruywagen, G. C. Du Toit, Elmari |
| author_sort | Du Toit, Elmari |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Dissertation (PhD)--University of Stellenbosch, 2001. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/52127 |
| institution | Stellenbosch University (South Africa) |
| language | en_ZA |
| last_indexed | 2026-06-10T12:43:20.403Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2012 |
| publishDateRange | 2012 |
| publishDateSort | 2012 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/52127 A quantitative bio-economic investigation of inshore fisheries Du Toit, Elmari Cruywagen, G. C. Van Vuuren, J. H. Stellenbosch University. Faculty of Science. Dept. of Mathematical Sciences (applied, computer, mathematics). Renewable natural resources -- Mathematical models Fishery management -- Mathematical models Biology, Economic -- Mathematical models Jasus lalandii -- Economic aspects. -- Mathematical models Dissertations -- Applied mathematics South African Cape Rock Lobster Theses -- Applied mathematics Dissertation (PhD)--University of Stellenbosch, 2001. ENGLISH ABSTRACT: The efficient management of renewable resources may ensure sustainable income to communities and countries. In the past the mathematical modelling used in the management decisions, in South Africa, was based on biological considerations only. In this thesis we include economic factors in the models and aim to determine steady state harvesting levels such that a maximum present value of all future revenues may be reached. A bio-economical approach is followed throughout the study and applied to the South African Cape Rock Lobster (Jasus lalandii) resource. We first address the problem using the simplest surplus production models. The model is applied to the Cape Rock Lobster, finding that the economical factors do indeed influence the steady state results, emphasising that they should be incorporated in the modelling process. A more descriptive two-sex-delay-difference model is then applied, which includes delay times for juveniles to reach sexual maturity and distinguishes between sexes. Yet further involved stage-class models are also studied and we propose a solution to the non-linear programming problem reached. These models may assist decision makers in future as knowledge on, for example, the growth of the two sexes, proper size limits and the influence of price differences are gained. Finally, we propose a harvesting strategy where catch is taken from alternative spatial lanes and apply here results from reaction diffusion theory. This theoretical approach might provide guidelines to new and underdeveloped fisheries in future, but also influence current inshore fisheries towards new management strategies. AFRIKAANSE OPSOMMING: Die doeltreffende bestuur van hernubare hulpbronne kan 'n volhoubare ekonomiese opbrengs aan gemeenskappe en lande verseker. In die verlede is die wiskundige modelle wat in die besluitnemingsproses gebruik is, in Suid Afrika, gebaseer op biologiese oorwegings alleen. In hierdie studie word ook ekonomiese faktore in die modelle ingesluit en word ewewigstoestande bepaal vir vangste, sodanig dat 'n maksimum huidige waarde van toekomstige inkomste uit 'n vissery bereik word. 'n Bio-ekonomiese benadering word deurgaans gevolg en modelle word toegepas op die Suid-Afrikaanse Weskus Kreefbron (Jasus lalandii). Die studie begin deur basiese surplus produksie modelle te gebruik. Die resultate van die toepassing op die Weskus Kreefbron toon dat die ekonomiese faktore 'n groot invloed op die voorgestelde ewewigstoestand van die populasie het. Dit benadruk dus die feit dat hierdie faktore in die modelleringsproses ingesluit behoort te word. Meer beskrywende twee-geslag-vertragings-verskil modelle word daarna toegepas, en sluit in 'n vertragings periode vir vis om 'n volwasse stadium te bereik. Hierdie tydfaktor verskil dikwels vir mannetjies en wyfies en daarom word hier 'n twee-geslag model gebruik. Meer gevorderde klasse modelle word ook bespreek. Ons stel 'n oplossing vir hierdie nie-lineêre programmeringsprobleem voor. Hierdie gevorderde modelle mag in die toekoms handige hulpmiddels wees wanneer inligting rakende 'n spesie gesoek word. Sulke inligting mag insluit die groeitempos van mannetjies en wyfies, geskikte grootte beperkings vir vangste en die invloed van prysverskille vir verskillende groottes vis. 'n Nuwe vangste strategie word ook voorgestel waar vangste slegs geneem word uit alternatiewe ruimtelike bane en pas ons hier resultate uit die reaksie-diffusie teorie toe. Hierdie teoretiese oplossings mag riglyne bied wanneer nuwe visserye in die toekoms ontgin word, maar ook huidige visserye beïnvloed in die rigting van 'n nuwe bestuur strategie. Doctoral 2012-08-27T11:34:51Z 2012-08-27T11:34:51Z 2001-11 Thesis http://hdl.handle.net/10019.1/52127 en_ZA Stellenbosch University 204 p. application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Renewable natural resources -- Mathematical models Fishery management -- Mathematical models Biology, Economic -- Mathematical models Jasus lalandii -- Economic aspects. -- Mathematical models Dissertations -- Applied mathematics South African Cape Rock Lobster Theses -- Applied mathematics Du Toit, Elmari A quantitative bio-economic investigation of inshore fisheries |
| title | A quantitative bio-economic investigation of inshore fisheries |
| title_full | A quantitative bio-economic investigation of inshore fisheries |
| title_fullStr | A quantitative bio-economic investigation of inshore fisheries |
| title_full_unstemmed | A quantitative bio-economic investigation of inshore fisheries |
| title_short | A quantitative bio-economic investigation of inshore fisheries |
| title_sort | quantitative bio economic investigation of inshore fisheries |
| topic | Renewable natural resources -- Mathematical models Fishery management -- Mathematical models Biology, Economic -- Mathematical models Jasus lalandii -- Economic aspects. -- Mathematical models Dissertations -- Applied mathematics South African Cape Rock Lobster Theses -- Applied mathematics |
| url | http://hdl.handle.net/10019.1/52127 |
| work_keys_str_mv | AT dutoitelmari aquantitativebioeconomicinvestigationofinshorefisheries AT dutoitelmari quantitativebioeconomicinvestigationofinshorefisheries |