Length Frequency Distribution, Mortality Rate and Reproductive Biology of Kawakawa (Euthynnus affinis-Cantor, 1849) in the Coastal Waters of Tanzania

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dc.contributor.authorJohnson, M. G.
dc.contributor.authorTamatamah, Rashid A.
dc.date.accessioned2016-07-08T12:34:59Z
dc.date.available2016-07-08T12:34:59Z
dc.date.issued2013
dc.description.abstractThis study explored important aspect of the basis for the highly complex population of kawakawa (Euthynnus affinis) within the coastal waters of Tanzania; by investigating length frequency distribution, mortality rate and reproductive characteristics. This information is essential for the sustainable management of the regionally-important recreational and economic E. affinis fishery. Fish were sampled on a monthly basis for two monsoon seasons using a ring net and artisanal fishermen boat. Maximum and minimum total length was 85 and 31 cm, respectively. Nonlinear least square fitting provided a complete set of von Bertalanffy growth estimates: L8 = 89.25 cm total length and K = 0.78. The estimated value of total mortality based on length converted catch curve using these growth parameters is Z = 1.78 year(-1). Natural mortality based on growth parameters and mean environmental temperature (T = 26.9 degrees C) is M = 1.09 year(-1). The estimated annual instantaneous fishing mortality (F = 0.69 year(-1)) was considerably grater than the target (Fopt = 0.43 year(-1)) and limit (Flimit = 0.58 year(-1)) biological reference point indicating that E. affinis is heavily overexploited. Reproductive aspects were assessed whereby female E. affinis was reported to reach maturity earlier than males which is an indication of phenotypic response toward a decline in population. Two peaks was revealed by the use of Gonad-Somatic Index (GSI), however an extended spawning period was noticed in a period between November to February following an increased water temperature. Although, these findings presents a snapshot concerning population structure and reproduction of E. affinis, further studies covering the entire coastal waters of Tanzania are recommended to aid the management and conservation strategiesen_US
dc.identifier.citationJohnson, M.G. and Tamatamah, A.R., 2013. Length frequency distribution, mortality rate and reproductive biology of kawakawa (Euthynnus affinis-Cantor, 1849) in the coastal waters of Tanzania. Pakistan Journal of Biological Sciences, 16(21), p.1270.en_US
dc.identifier.doi10.3923/pjbs.2013.1270.1278
dc.identifier.urihttp://hdl.handle.net/20.500.11810/2964
dc.language.isoenen_US
dc.subjectEuthynnus affinisen_US
dc.subjectMortalityen_US
dc.subjectOver-exploiteden_US
dc.subjectFishing mortalityen_US
dc.subjectTanzaniaen_US
dc.titleLength Frequency Distribution, Mortality Rate and Reproductive Biology of Kawakawa (Euthynnus affinis-Cantor, 1849) in the Coastal Waters of Tanzaniaen_US
dc.typeJournal Article, Peer Revieweden_US
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