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.

Key words: Fishing pressure, marine protected areas, phenotypic plasticity, resilience