SPATIAL VARIATION IN GROWTH AND MORTALITY PARAMETERS OF THE MARBLED PARROTFISH, LEPTOSCARUS VAIGIENSIS ON VARIABLY PROTECTED REEFS IN KENYA

Abstract

Growth and mortality variations of Leptoscarus vaigiensis was studied among six reef sites exposed to different fishing pressure in coastal Kenya in order to test the hypothesis of phenotypic plasticity. Monthly fish samples were obtained from marine parks (protected no-take areas), marine reserves (partially protected areas) and non-protected reefs from May 2011 to April 2013, and were measured for total lengths (cm) and body weights (g). Growth (K, L∞) and mortality (Z, M, F) parameters of the species were determined using the ELEFAN I program and compared between sites. Results showed higher asymptotic length (L∞) estimate (~ 31 cm) for parrotfish from a reserve site and lowest estimate (26-27 cm) from a marine park site. Fish from park sites had equal but lowest growth rates (K yr-1) of 0.46 compared to 1.73 ± 0.11 and 1.36 ± 0.84 for fish from park and reserve sites, respectively. Total mortality estimates (Z yr-1) were lower for protected areas (1.69-1.96) and higher for reserve (2.87-9.15) and non-protected (4.39-5.30) sites. This study showed divergence of growth parameters of a coral reef fish exposed to different levels of fishing pressure, thereby providing insights into the possibility of utilizing the parameters as indicators of environmental stress.