Growth, Mortality Parameters and Exploitation Rate of West African Ilisha (<i>Ilisha africana</i> Bloch, 1795, Clupeidae) off Benin Coastal Waters (West Africa): Implications for Management and Conservation

Abstract

West African Ilisha was the third most abundant species of Clupeidae off Benin coastal waters after Sardinella spp and Ethmalosa frimbriata . The fishing effort of these fisheries increased with a dominance of small-sized specimens in the catches. This paper allowed updating some demographic parameters and the exploitation rate of Ilisha africana collected between July 2013 and June 2014 from the coastal waters of Benin for management and conservation of these fisheries. The growth pattern showed a negative allometric growth with an abundance of small-sized specimens. The von Bertalanffy growth function (VBGF) estimations were: L ∞ = 21.31 cm standard length; K = 1.20 year -1 ; and t 0 = -0.138 year. The total mortality rate ( Z ), natural mortality rate ( M ) and fishing mortality rate ( F ) were 4.040 year -1 , 2.27 year -1 and 1.77 year -1 respectively. The Z / K ratio was 3.667 and the exploitation rate ( E = F/Z ) was 0.44 showing an under exploitation of this species. The estimated potential longevity ( t max ) was 2.5 years. In addition, the fisheries management should be devolved from the state to the local level to compel fishermen to take greater responsibility for the sustainability and conservation of the fisheries such as size-limit regulation by gradually increasing fishing gears mesh size.