The application of general linear modelling methods to estimate trends in abundance of the hake and rock lobster stocks off South Africa

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dc.contributor.advisorButterworth, Doug S
dc.contributor.authorGlazer, Jean Patricia
dc.date.accessioned2016-01-15T14:15:10Z
dc.date.available2016-01-15T14:15:10Z
dc.date.issued1999en_ZA
dc.descriptionBibliography: pages 162-178.en_ZA
dc.description.abstractThe two species of Cape hake, Merluccius capensis (shallow-water hake) and M paradoxus (deepwater hake), fomi the mainstay of the bottom trawl industry off South Africa and constitute the country's most valuable fishery. It is therefore important that the status of this resource be assessed regularly to ensure that exploitation is at a sustainable level. The two Cape hake species are morphologically similar and no distinction is made between them in commercial catch statistics. Consequently, for assessment purposes, the Cape hakes are treated as a single species. It is assumed that two stocks of Cape hake exist, one off the West Coast and another off the South Coast of South Africa. Central to the assessments of these stocks are the catch per unit effort (CPUE) data because it assumed that CPUE is proportional to abundance. The nominal CPUE (hake catch divided by actual time trawled) for both the West and South Coast stocks has shown a steady growth over the period 1978 - 1994, increasing at a rate of 3.8% per annum on the West Coast and 4.2% per annum on the South Coast. The bulk of this thesis is concerned with determining whether these increases in CPUE are the result of an increasing biomass, or are rather, in part, the result of improved vessel efficiency due to technological advancement or of changes in fishing strategy. The existing CPUE time series had previously been standardised by means of applying power factors which were crudely estimated in the early 1970s and which are likely inappropriate for the current fishing fleets. These CPUE series have therefore been re-standardised by applying the internationally accepted approach of General Linear Modelling (GLM).en_ZA
dc.identifier.apacitationGlazer, J. P. (1999). <i>The application of general linear modelling methods to estimate trends in abundance of the hake and rock lobster stocks off South Africa</i>. (Thesis). University of Cape Town ,Faculty of Science ,Department of Mathematics and Applied Mathematics. Retrieved from http://hdl.handle.net/11427/16395en_ZA
dc.identifier.chicagocitationGlazer, Jean Patricia. <i>"The application of general linear modelling methods to estimate trends in abundance of the hake and rock lobster stocks off South Africa."</i> Thesis., University of Cape Town ,Faculty of Science ,Department of Mathematics and Applied Mathematics, 1999. http://hdl.handle.net/11427/16395en_ZA
dc.identifier.citationGlazer, J. 1999. The application of general linear modelling methods to estimate trends in abundance of the hake and rock lobster stocks off South Africa. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Glazer, Jean Patricia AB - The two species of Cape hake, Merluccius capensis (shallow-water hake) and M paradoxus (deepwater hake), fomi the mainstay of the bottom trawl industry off South Africa and constitute the country's most valuable fishery. It is therefore important that the status of this resource be assessed regularly to ensure that exploitation is at a sustainable level. The two Cape hake species are morphologically similar and no distinction is made between them in commercial catch statistics. Consequently, for assessment purposes, the Cape hakes are treated as a single species. It is assumed that two stocks of Cape hake exist, one off the West Coast and another off the South Coast of South Africa. Central to the assessments of these stocks are the catch per unit effort (CPUE) data because it assumed that CPUE is proportional to abundance. The nominal CPUE (hake catch divided by actual time trawled) for both the West and South Coast stocks has shown a steady growth over the period 1978 - 1994, increasing at a rate of 3.8% per annum on the West Coast and 4.2% per annum on the South Coast. The bulk of this thesis is concerned with determining whether these increases in CPUE are the result of an increasing biomass, or are rather, in part, the result of improved vessel efficiency due to technological advancement or of changes in fishing strategy. The existing CPUE time series had previously been standardised by means of applying power factors which were crudely estimated in the early 1970s and which are likely inappropriate for the current fishing fleets. These CPUE series have therefore been re-standardised by applying the internationally accepted approach of General Linear Modelling (GLM). DA - 1999 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 1999 T1 - The application of general linear modelling methods to estimate trends in abundance of the hake and rock lobster stocks off South Africa TI - The application of general linear modelling methods to estimate trends in abundance of the hake and rock lobster stocks off South Africa UR - http://hdl.handle.net/11427/16395 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/16395
dc.identifier.vancouvercitationGlazer JP. The application of general linear modelling methods to estimate trends in abundance of the hake and rock lobster stocks off South Africa. [Thesis]. University of Cape Town ,Faculty of Science ,Department of Mathematics and Applied Mathematics, 1999 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/16395en_ZA
dc.language.isoengen_ZA
dc.publisher.departmentDepartment of Mathematics and Applied Mathematicsen_ZA
dc.publisher.facultyFaculty of Scienceen_ZA
dc.publisher.institutionUniversity of Cape Town
dc.subject.otherMathematics and Applied Mathematicsen_ZA
dc.titleThe application of general linear modelling methods to estimate trends in abundance of the hake and rock lobster stocks off South Africaen_ZA
dc.typeMaster Thesis
dc.type.qualificationlevelMasters
dc.type.qualificationnameMScen_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceThesisen_ZA
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