An assessment of the reliability of fossil pilchard and anchovy scales as fish population indicators off Namibia

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dc.contributor.advisorJohnson, R Fen_ZA
dc.contributor.authorShackleton, L Yen_ZA
dc.date.accessioned2016-09-25T16:52:59Z
dc.date.available2016-09-25T16:52:59Z
dc.date.issued1986en_ZA
dc.description.abstractFossil fish scales hold potential for ellucidating past fish population fluctuations. A system of classification for scales from the pilchard, Sardinops ocellata, and the anchovy, Engraulis capensis, is presented. Both species show an unexpected range of scale types. The classifications reduce errors in distinguishing between the scales of the two species to ±2,5%. Scale loss from these fish is quantified under laboratory conditions. Pilchard lose 1,56 scales/fish/day due to death and 1,50 scales/fish/day due to deciduousness over their expected lifetimes. For anchovy the figures are 2,42 scales/fish/day (death) and 0,48 scales/fish/day (deciduousness). Application of these scale-loss studies to scales preserved in the anaerobic sediments off Walvis Bay, Namibia, shows that deciduousness is the dominant process contributing scales to the sediments. This basic information on pilchard and anchovy scale loss is used to interpret counts of scales in the laminated interval of a core taken from the diatomaceous muds off Walvis Bay. This pilot study shows that: i) the Namibian Fishery was dominated by pilchard in the past as it was prior to the collapse in the early 1970's and, because of this, is distinctly different from the anchovy/anchovetta-dominated east Pacific systems; and ii) major pre-fishery stock fluctuations do appear to be reflected in the sedimentary record. Further scale studies on larger sediment samples are recommended to ellucidate the Namibian fish stock fluctuations.en_ZA
dc.identifier.apacitationShackleton, L. Y. (1986). <i>An assessment of the reliability of fossil pilchard and anchovy scales as fish population indicators off Namibia</i>. (Thesis). University of Cape Town ,Faculty of Science ,Department of Oceanography. Retrieved from http://hdl.handle.net/11427/21941en_ZA
dc.identifier.chicagocitationShackleton, L Y. <i>"An assessment of the reliability of fossil pilchard and anchovy scales as fish population indicators off Namibia."</i> Thesis., University of Cape Town ,Faculty of Science ,Department of Oceanography, 1986. http://hdl.handle.net/11427/21941en_ZA
dc.identifier.citationShackleton, L. 1986. An assessment of the reliability of fossil pilchard and anchovy scales as fish population indicators off Namibia. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Shackleton, L Y AB - Fossil fish scales hold potential for ellucidating past fish population fluctuations. A system of classification for scales from the pilchard, Sardinops ocellata, and the anchovy, Engraulis capensis, is presented. Both species show an unexpected range of scale types. The classifications reduce errors in distinguishing between the scales of the two species to ±2,5%. Scale loss from these fish is quantified under laboratory conditions. Pilchard lose 1,56 scales/fish/day due to death and 1,50 scales/fish/day due to deciduousness over their expected lifetimes. For anchovy the figures are 2,42 scales/fish/day (death) and 0,48 scales/fish/day (deciduousness). Application of these scale-loss studies to scales preserved in the anaerobic sediments off Walvis Bay, Namibia, shows that deciduousness is the dominant process contributing scales to the sediments. This basic information on pilchard and anchovy scale loss is used to interpret counts of scales in the laminated interval of a core taken from the diatomaceous muds off Walvis Bay. This pilot study shows that: i) the Namibian Fishery was dominated by pilchard in the past as it was prior to the collapse in the early 1970's and, because of this, is distinctly different from the anchovy/anchovetta-dominated east Pacific systems; and ii) major pre-fishery stock fluctuations do appear to be reflected in the sedimentary record. Further scale studies on larger sediment samples are recommended to ellucidate the Namibian fish stock fluctuations. DA - 1986 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 1986 T1 - An assessment of the reliability of fossil pilchard and anchovy scales as fish population indicators off Namibia TI - An assessment of the reliability of fossil pilchard and anchovy scales as fish population indicators off Namibia UR - http://hdl.handle.net/11427/21941 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/21941
dc.identifier.vancouvercitationShackleton LY. An assessment of the reliability of fossil pilchard and anchovy scales as fish population indicators off Namibia. [Thesis]. University of Cape Town ,Faculty of Science ,Department of Oceanography, 1986 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/21941en_ZA
dc.language.isoengen_ZA
dc.publisher.departmentDepartment of Oceanographyen_ZA
dc.publisher.facultyFaculty of Scienceen_ZA
dc.publisher.institutionUniversity of Cape Town
dc.subject.otherOceanographyen_ZA
dc.titleAn assessment of the reliability of fossil pilchard and anchovy scales as fish population indicators off Namibiaen_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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