Population structure, growth performance and mortality rates of the freshwater clam Galatea paradoxa (Born, 1778) in Nun River, Nigeria

The shell length-growth and mortality parameters of the freshwater clam, Ga latea paradoxa (Born, 1778) (Lamellibranchia, Donacidae) from Nun River, Ni geria, were investigated. Maximum observed age and size were 7 yr and 10.6 cm respectively. Mean length at ages 1 to 7 yr were 5.3, 6.4, 7.2, 7.9, 8.3 , 8.9 and 9.1 cm respectively Growth conformed to the von Bertalanffy's gro wth model, with the parameters L-infinity = 10.2 cm, K = 0.254.yr(-1) and t (0) = 1.874 yr. Instantaneous total mortality rate was estimated at Z = 0.8 07.yr(-1); instantaneous mortality rates due to natural causes and fishing were M = 0.301.yr(-1) and F = 0.506.yr(-1) respectively. The exploitation r ate (E = 0.627) suggest that this stock of G. paradoxa is overfished.