Aspects of the dynamics of the inshore and offshore populations of Brachydeuterus auritus (Family: Haemulidae) in Ghana

Abstract

Growth and mortality parameters of the bigeye grunt populations in Ghana were estimated from length-frequency data collected between November 1993 and October 1995. Tlie von Bertalanffy growlli parameters, L„, K and t^, were estimated as 23.0 cm TL , 1.20 yr"' and - 0.14 yr, respectively, lor tiie inshore population, and 22.7 cmTL, 1.16 yr"' and -0.15 yr, respectively, for the offshore population. The growth performance index was calculated as 2.80 for the inshore population and 2.78 for the offsiiore population. Estimates of the mortality coefficients were: Z = 6.40 yr"', M = 2.14 yr"' and F = 4,26 yr"' for the inshore population, and Z = 6.40 yr"', M - 2.10 yr ' and F = 4.30 yr"' for the offshore population. Similar estimates of the exploitation rate (F = 0.67) were obtained for the two populations. This value exceeds the optimum (E„p,) of 0.46 and 0.57 derived by the yield-per-recruit analysis for the inshore and offshore populations, respectively. These observations suggest the over-exploitation of the D. auritus populations