Age, Growth, Mortality and Condition Factor Study of Gnathonemus Tamandua (Gunther, 1862) from the Fresh Water Reaches of Lower Nun River, Niger Delta, Nigeria

J.F.N. Abowei ； O.A.Davies

《Current Research Journal of Biological Sciences》 1卷1期 (2009/07) Pp. 28-34

並列摘要

Age, growth and mortality of Gnathonemus tamandua from the fresh water reaches of lower Nun River Niger Delta Nigeria was studied for one year, using five hundred specimens. The maximum length at age attained L(subscript max), was 38.2 cm weighing 305.2 g. The length attained at infinity (L (subscript ∞)) was 37.0 cm. Growth exponent (b) was 2.74. Length performance index (θ^1) value was 2.31. Weight performance index value (Ø) was 1.96. The growth coefficient (K) value was 0.32. The hypothetical age at which length is zero (T(subscript o) was -0.44 and the maximum age estimated was 4 years. There was no temporal variation in the condition of the fish throughout the year with condition index value ranging from 0.83-1.00 and condition factor value of 0.92. Total mortality (Z) value was l.2yr^(-1). Natural Mortality (M) value was 0.1.3; fishing mortality (F) value was 0.40; value for the rate of exploitation was 0.30 with corresponding percentage value of 30. G. tamandua population from the fresh water reaches of the lower Nun River was below the optimal value for sustainable yield, for the exploitation of the fishery. It is therefore stands the risk of under exploitation if urgent measures are not taken to develop the fishery.

並列關鍵字

Gnathonemus tamandua ； length ； weight ； mortality ； condition factor ； performance index ； Nun River