Some population parameters and exploitation rate of Ethmalosa fimbriata (Pisces: Clupeidae) in the coastal marine habitat of Ogun State, South-West, Nigeria

Abstract

Most aquatic ecosystem services are in a state of decline and the harmful consequences of this decline could grow significantly worse if efficient management strategies and policies are not put in place. The growth and mortality parameters as well as exploitation rate of 2,121 Ethmalosa fimbriata were collected between February 2015 and January 2017 from Ogun marine coastal water for management and conservation studies. Growth parameters and performance index estimated based on the Von Bertalanffy model using routines in ELEFAN1 FiSAT II gave the asymptotic length (L∞) of 32.6cm, the growth coefficient (K) of 0.65yr^-1, the theoretical age at length zero 0.35^-1 and the performance index ɸ of 2.8^-1. E. fimbriata grew allometrically (negative) with an abundance of medium size specimens. This species indicated a bi-modal distribution of two cohorts within the population structure. The estimated average value of instantaneous rate of total mortality was 2.69^-1, natural mortality was 1.33^-1, giving fishing mortality of 1.36y^-1 and the rate of exploitation, E at 0.51yr^-1 indicating over-exploitation of the stock of this species. Therefore, some management actions are considered necessary for sustainable exploitation and conservation of this commercially important species of fish.