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

Age, g rowth and mortality of Gnathonemus tamandua from the fresh water reaches of lower NunRiver Niger Delta Nigeria was stu died for one year, us ing five hun dred specimens . The maximum length at ageattained Lmax was 38.2 cm weighing 305.2 g. The length a t t ained at infinity (L 4) was 37.0 cm. Growthexponent (b) was 2.74. Length p erformance index ( 21) value was 2.31. Weight performance index value ( )was 1.96. The growth co efficient (K) value was 0.32. The hypoth etical age at which length is zero (To) was–0.44 and th e maximum age es timated was 4 years. Th ere was no temporal variation in the condition of the fishthroughout the year with condition index value ranging from 0.83 – 1.00 an d co ndition facto r value of 0.92.Total mortality (Z) value was 1.2yr!1. Natural Mortality (M) value was 0.1.3; fish ing mortality (F) value was0.40; value fo r th e rate of exp lo it a t ion was 0.30 with co rresponding percentage value of 30. G. tamanduapopulation from the fresh water reaches o f the lower Nun River was below the optimal value for s us tainableyield, for the exploitation of the fish ery. It is th erefore stands the risk of under exploitation if urgent measuresare not taken to develop the fishery.