Thursday, 9 July 2015

Age, Growth and Mortality of Tylochromis jentinki (Steindachner, 1895) in Ebrié Lagoon, Ivory Coast



Age, Growth and Mortality of Tylochromis jentinki (Steindachner, 1895) in Ebrié Lagoon, Ivory Coast
Kouadio Justin Konan1, Soumaïla Sylla2, Marie Anne D’Almeida3, Boua Célestin Atsé4
First Author1, Second Author2

1,2,4Centre de Recherches Océanologiques, 29, rue des pêcheurs-BP V 18 Abidjan, Côte d’Ivoire
3Laboratoire de Biologie cellulaire, UFR Biosciences, Université Félix Houphouët Boigny-22 BP 582 Abidjan 22, Côte d’Ivoire
Abstract Monthly data of length composition for Tylochromis jentinki (Steindachner, 1895), landed between February 2004 and January 2006 in Ebrié Lagoon (Ivory Coast) were used to estimate the growth, mortality and exploitation parameters of the stock. A total of 1850 individuals ranging from 7.5 to 23.5 cm SL (standard length), were examined. Length frequency data were analyzed with FiSAT software using the ELEFAN 1 package to estimate the population parameters. We estimated von Bertalanffy growth parameters: L∞ = 25.00 cm, K = 0.67 year-1, and t0 = -0.28 year-1, with the growth performance index, φ’ of 2.62. The length-weight relationship was W = 0.0215 x SL2.98 and described isometric growth for the species with an asymptotic weight (W∞) = 314.99 g. Total mortality (Z) estimated from catch-curve analyses was = 2.38 year-1. Natural mortality based on growth parameters and mean environmental temperature (T = 28ºC) was M = 1.45 year-1. Furthermore, the fishing mortality rate of 0.93 year-1 was by far in excess of the precautionary target (Fopt = 0.73 year-1) and slightly under the limit (Flimit = 0.97 year-1) biological reference points. With this level of mortality and exploitation level (E = 0.39 < 0.50), the stock was under-exploited.
Keywords Age, growth, Cichlidae, exploitation, recruitment, length frequency.

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