Population parameters and exploitation rate of Sarotherodon galilaeus galilaeus (Cichlidae) in Lakes Doukon and Togbadji, Benin

Abstract

Growth, mortality, recruitment and relative yield per recruit of Sarotherodon galilaeus galilaeus from Lakes Doukon and Togbadji were studied. Data on total length, total weight and sex were recorded on a monthly basis between January and December 2013 for S. g. galilaeus captured by local fishers. The estimated asymptotic lengths L_∞ were 26.2 and 23.6 cm for Lakes Doukon and Togbadji, respectively, while the growth rate K was 0.73 in Lake Doukon and 0.87 in Lake Togbadji. Estimates of fishing mortality, 0.27 and 0.47 y⁻¹ for Doukon and Togbadji, respectively, were low relative to natural mortality, 1.51 and 1.74 y⁻¹, respectively. Sizes at first sexual maturity were 12.8 and 13.2 cm for females and males, respectively, in Lake Doukon, and 11.5 and 12.4 cm for females and males, respectively, in Lake Togbadji. The size at first capture was estimated at 13.3 and 12.7 cm for Lakes Doukon and Togbadji, respectively, which, in the light of the size at maturity estimates, indicates that fish spawn at least once before capture. The current exploitation rates of 0.15 for Lake Doukon and 0.21 for Lake Togbadji suggest that their stocks of S. g. galilaeus are not overexploited in either lake.

Keywords: cichlids, ELEFAN, fisheries, Mono River, size-at-maturity, selectivity, West Africa