Biology of Albacore tuna (Thunnus alalunga, Bonnaterre 1788) off the South West Coast of South Africa

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dc.contributor.advisorAttwood, Colinen_ZA
dc.contributor.advisorMarsac, Francisen_ZA
dc.contributor.authorNorman, Stewart Jamesen_ZA
dc.date.accessioned2014-08-20T19:21:53Z
dc.date.available2014-08-20T19:21:53Z
dc.date.issued2013en_ZA
dc.description.abstractAlbacore tuna (Thunnus alalunga) is a highly migratory species found in all of the worlds oceans. The origin of albacore south of Africa is in question. This species constituted 85% of catches of the South African commercial tuna fishing fleet from 2000-2009 and is an important species in supporting a large boat-based recreational fishery. Albacore were sampled at angling competitions, which offer a repeatable and cheap source of tuna, in the Western Cape of South Africa during 2012 and 2013. 119 Samples were used to determine a length-weight relationship and to provide conversion ratios of various body measurements to fork length when total length was not available. Visual examination of testes and ovaries indicated that albacore are not spawning off the coast of South Africa.A comparison between the ease of using sectioned sagittal otoliths and first dorsal spines indicated that otoliths were more precise for estimating the age of albacore. Von Bertalanffy growth parameters were estimated from 51 fish, ranging from 2-9 years old (L∞=1100.07 mm; K=0.238 y-1; t₀=-2.14). Stomach content analysis indicated that the mesopelagic squid Lycoteuthis lorigera is the most important prey item for South African albacore. δ13C and δ15N stable isotope analysis of albacore and yellowfin tuna (T. albacares) muscle tissue showed that they feed on prey that may depend on different primary producers but that the two species of tuna share the same niche in the southern Benguela food web. Trophic levels of 3.8 and 3.76 were assigned to albacore and yellowfin tuna respectively.en_ZA
dc.identifier.apacitationNorman, S. J. (2013). <i>Biology of Albacore tuna (Thunnus alalunga, Bonnaterre 1788) off the South West Coast of South Africa</i>. (Thesis). University of Cape Town ,Faculty of Science ,Department of Biological Sciences. Retrieved from http://hdl.handle.net/11427/6632en_ZA
dc.identifier.chicagocitationNorman, Stewart James. <i>"Biology of Albacore tuna (Thunnus alalunga, Bonnaterre 1788) off the South West Coast of South Africa."</i> Thesis., University of Cape Town ,Faculty of Science ,Department of Biological Sciences, 2013. http://hdl.handle.net/11427/6632en_ZA
dc.identifier.citationNorman, S. 2013. Biology of Albacore tuna (Thunnus alalunga, Bonnaterre 1788) off the South West Coast of South Africa. University of Cape Town.en_ZA
dc.identifier.ris TY - Thesis / Dissertation AU - Norman, Stewart James AB - Albacore tuna (Thunnus alalunga) is a highly migratory species found in all of the worlds oceans. The origin of albacore south of Africa is in question. This species constituted 85% of catches of the South African commercial tuna fishing fleet from 2000-2009 and is an important species in supporting a large boat-based recreational fishery. Albacore were sampled at angling competitions, which offer a repeatable and cheap source of tuna, in the Western Cape of South Africa during 2012 and 2013. 119 Samples were used to determine a length-weight relationship and to provide conversion ratios of various body measurements to fork length when total length was not available. Visual examination of testes and ovaries indicated that albacore are not spawning off the coast of South Africa.A comparison between the ease of using sectioned sagittal otoliths and first dorsal spines indicated that otoliths were more precise for estimating the age of albacore. Von Bertalanffy growth parameters were estimated from 51 fish, ranging from 2-9 years old (L∞=1100.07 mm; K=0.238 y-1; t₀=-2.14). Stomach content analysis indicated that the mesopelagic squid Lycoteuthis lorigera is the most important prey item for South African albacore. δ13C and δ15N stable isotope analysis of albacore and yellowfin tuna (T. albacares) muscle tissue showed that they feed on prey that may depend on different primary producers but that the two species of tuna share the same niche in the southern Benguela food web. Trophic levels of 3.8 and 3.76 were assigned to albacore and yellowfin tuna respectively. DA - 2013 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PB - University of Cape Town PY - 2013 T1 - Biology of Albacore tuna (Thunnus alalunga, Bonnaterre 1788) off the South West Coast of South Africa TI - Biology of Albacore tuna (Thunnus alalunga, Bonnaterre 1788) off the South West Coast of South Africa UR - http://hdl.handle.net/11427/6632 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/6632
dc.identifier.vancouvercitationNorman SJ. Biology of Albacore tuna (Thunnus alalunga, Bonnaterre 1788) off the South West Coast of South Africa. [Thesis]. University of Cape Town ,Faculty of Science ,Department of Biological Sciences, 2013 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/6632en_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.titleBiology of Albacore tuna (Thunnus alalunga, Bonnaterre 1788) off the South West Coast of 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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