Growth and mortality of sleeper fish, Bostrychus africanus from upper new Calabar river, Rivers state, Nigeria

Abstract

Bostrychus africanus samples were collected over a period of twenty months (January 2015 to August 2016) from the Upper New Calabar River. This was aimed at ascertaining the present state of the stock following increased exploitation Analyses were run using the FISAT package. Growth estimates by the Von Bertalanffy equation showed that mean length infinity was 19.69.±1.5795cm,, growth coefficient (parameter of curvature (K) was 1.37±0.9595cm/year,, t_max value obtained was 2.3±0.94295 years,. Recruitment analysis showed that the mean relative yield per recruit was 0.063±0.007 and biomass per recruit as 0.45±0.134. Exploitation rate was 0.395±0.088, while mortality estimates calculated by length converted catch curves and Pauly’s equation showed that total mortality was 4.01±2.84, natural mortality 2.25±1.21 and mean fishing mortality was 1.75±1.64. Exploitation was found to be inadequate, judging from the values of the natural and fishing mortalities. This was corroborated by the figures obtained for the prevailing exploitation rate.

Key Words: Growth, mortality, population, recruitment, exploitation, sleeper fish