Growth and mortality parameters of the black-chinned tilapia Sarotherodon melanotheron melanotheron (Pisces: Cichlidae) in a small lagoon in the Central Region of Ghana

Abstract

This study quantified growth, mortality, and exploitation rate of the black-chinned tilapia (Sarotherodon melanotheron melanotheron) population in Etsir Lagoon, a small brackish waterbody at Abandze (5°11′ N, 1°5′ W) in the Central Region of Ghana for management of the stock. Fish samples were collected monthly between April 2014 and March 2015, and specimens measured 3.9–13.8 cm SL with a mode in the 7.0–7.9 cm length class. Analysis of the length-frequency data of 861 specimens using the ELEFAN method indicated a growth constant (K) of 0.93 yr⁻¹, and asymptotic length (L_∞) of 14.3 cm SL for the population. The short lifespan (tmax = 3.2 years) determined for the species and estimated growth parameters suggest stunting in the population, as in other brackish water populations in Ghana. The total mortality (Z), natural mortality (M), and fishing mortality (F) coefficients: 5.09 yr⁻¹, 2.15 yr⁻¹ and 2.95 yr⁻¹, respectively, indicate fishing as a major contributor to total mortality. The calculated exploitation rate (E = 0.58) of the population suggests overexploitation of the stock, however, the all-yearround recruitment in the population probably ensures production at levels that compensate for its relatively high exploitation rate.

Keywords: Etsir Lagoon, growth and mortality parameters, population dynamics, recruitment, tilapiine fish