Management Indicators and Growth Performance Index of Tilapia Zillii in a Tropical Coastal Estuary

Abstract

An investigative study was carried-out on management indicators and growth performance index of T. zillii in a tropical coastal estuary for twenty-four consecutive months using length-weight data. Electronic length frequency analysis (ELEFAN), sub-routine of FiSAT II software and empirical models were used to analyse the data. Results showed that the mean size of T. zillii was between 22.10±1.155 cm and 26.10±0.115 cm in April and January respectively. The highest (349.72±2.725g) and lowest (264.14±4.109g) mean weights were recorded in the respective months of December and April. Exploited sizes ranged from 11-12 cm to 36-37 cm. Length class 24-25 cm was mostly exploited, constituting 9.92% while 36-37 cm length class was the least (0.05 %) on the exploitation data. Length-at-first maturity, Lm, length-at-optimum yield, Lopt, longevity, Tmax, and growth performance index were estimated as 10.23 cm, 23.95 cm, 4 years and 3.076 respectively. It was therefore, recommended that, for the fishery to be sustainable, close monitoring should be given during the months of February and April, and exploitation of larger size fish be regulated to prevent recruitment overfishing.