The development of an operational management procedure for the South African west coast rock lobster fishery

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dc.contributor.advisorButterworth, Doug S
dc.contributor.advisorStewart, Theodor J
dc.contributor.authorJohnston, Susan Joy
dc.date.accessioned2016-11-16T13:25:09Z
dc.date.available2016-11-16T13:25:09Z
dc.date.issued1998en_ZA
dc.description.abstractThis thesis considers the development of an operational management procedure (OMP) to provide scientific recommendations for commercial TAC for the South African west coast rock lobster (Jasus lalandii) fishery. This fishery has been under considerable stress in recent years as a result of overfishing and low somatic growth rates. Present catch levels, less than 2000 MT, are substantially smaller than levels recorded in the past. The present biomass (above 75mm carapace length) is estimated to be only six percent of the pristine level. At the start of this research, no long-term management strategy for the resource existed. Neither was there any robust, tested, scientific method available for setting the annual TAC for the fishery, which resulted in a time-consuming and unsatisfactory scientific debate each year in developing a series of ad hoc TAC recommendations. The work presented in this thesis is thus aimed at answering two important questions. i) Can an adequate mathematical model be developed as a basis to simulate the resource and its associated fishery? ii) Can a self-correcting robust OMP be developed for the resource? The first phase of this thesis is the development of a size-structured population model of the resource and the associated fishery. A size-structured model is necessary as lobsters are difficult to age and hence most of the data collected are on a size basis. Furthermore, important management issues, such as the legal minimum size which has changed over time, require a model able to take size-structure into account. This model is fitted to a wide range of data from the fishery, including CPUE (catch-per-unit-effort) and catch-at-size information, by maximising a likelihood function. The model is shown to fit reasonably well to all data, and to provide biologically plausible estimates for its six estimable parameters.en_ZA
dc.identifier.apacitationJohnston, S. J. (1998). <i>The development of an operational management procedure for the South African west coast rock lobster fishery</i>. (Thesis). University of Cape Town ,Faculty of Science ,Department of Biological Sciences. Retrieved from http://hdl.handle.net/11427/22567en_ZA
dc.identifier.chicagocitationJohnston, Susan Joy. <i>"The development of an operational management procedure for the South African west coast rock lobster fishery."</i> Thesis., University of Cape Town ,Faculty of Science ,Department of Biological Sciences, 1998. http://hdl.handle.net/11427/22567en_ZA
dc.identifier.citationJohnston, S. 1998. The development of an operational management procedure for the South African west coast rock lobster fishery. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Johnston, Susan Joy AB - This thesis considers the development of an operational management procedure (OMP) to provide scientific recommendations for commercial TAC for the South African west coast rock lobster (Jasus lalandii) fishery. This fishery has been under considerable stress in recent years as a result of overfishing and low somatic growth rates. Present catch levels, less than 2000 MT, are substantially smaller than levels recorded in the past. The present biomass (above 75mm carapace length) is estimated to be only six percent of the pristine level. At the start of this research, no long-term management strategy for the resource existed. Neither was there any robust, tested, scientific method available for setting the annual TAC for the fishery, which resulted in a time-consuming and unsatisfactory scientific debate each year in developing a series of ad hoc TAC recommendations. The work presented in this thesis is thus aimed at answering two important questions. i) Can an adequate mathematical model be developed as a basis to simulate the resource and its associated fishery? ii) Can a self-correcting robust OMP be developed for the resource? The first phase of this thesis is the development of a size-structured population model of the resource and the associated fishery. A size-structured model is necessary as lobsters are difficult to age and hence most of the data collected are on a size basis. Furthermore, important management issues, such as the legal minimum size which has changed over time, require a model able to take size-structure into account. This model is fitted to a wide range of data from the fishery, including CPUE (catch-per-unit-effort) and catch-at-size information, by maximising a likelihood function. The model is shown to fit reasonably well to all data, and to provide biologically plausible estimates for its six estimable parameters. DA - 1998 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 1998 T1 - The development of an operational management procedure for the South African west coast rock lobster fishery TI - The development of an operational management procedure for the South African west coast rock lobster fishery UR - http://hdl.handle.net/11427/22567 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/22567
dc.identifier.vancouvercitationJohnston SJ. The development of an operational management procedure for the South African west coast rock lobster fishery. [Thesis]. University of Cape Town ,Faculty of Science ,Department of Biological Sciences, 1998 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/22567en_ZA
dc.language.isoengen_ZA
dc.publisher.departmentDepartment of Biological Sciencesen_ZA
dc.publisher.facultyFaculty of Scienceen_ZA
dc.publisher.institutionUniversity of Cape Town
dc.subject.otherOperations Researchen_ZA
dc.subject.othermathematical modelsen_ZA
dc.titleThe development of an operational management procedure for the South African west coast rock lobster fisheryen_ZA
dc.typeDoctoral Thesis
dc.type.qualificationlevelDoctoral
dc.type.qualificationnamePhDen_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceThesisen_ZA
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