GROWTH, MORTALITIES AND EXPLOITATION RATES OF ALESTES BAREMOZE (JOANNIS, 1835), BRYCINUS NURSE (RÜPPELL, 1832) AND SCHILBE INTERMEDIUS (RÜPPELL 1832) FROM THE LOWER REACHES OF THE WHITE VOLTA RIVER (YAPEI), GHANA

Abstract

A six-month study was conducted from October 2011 to March 2012 to assess the biology and state of exploitation of three major species namely Alestes baremoze, Brycinus nurse and Schilbe intermedius from the lower reaches of the White Volta River (Yapei), Ghana. Routines in FAO-ICLARM Stock Assessment Tools II (FISAT II) were used to determine the growth and mortality parameters and exploitation rates (E) from the length-frequency data generated from the landing surveys. Alestes baremoze had asymptotic length (TL∞) of 46.73cm and growth rate (K) of 0.94 year-1. Brycinus nurse had TL∞=28.38 cm, K= 1.10 year-1 whereas Schilbe intermedius had TL∞=27.93 cm, K=0.95 year-1. Brycinus nurse which was the third most abundant species among landings composition was being exploited at a rate of 0.77, above the optimal exploitation rate (E0.5). Alestes baremoze which was the most abundant species had exploitation rate of 0.30 whilst Schilbe intermedius had the exploitation rate (E) of 0.36. Both species populations in the lower reaches of the White Volta River are thus under exploited.