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

Growth and mortality parameters of the bigeye grunt populations in Ghana were estimated from length-frequency data collected between November 1993 and October 1995. The von Bertalanffy growth parameters, L4, K and to, were estimated as 23.0 cm TL, 1.20 yr-1 and - 0.14 yr, respectively, for the inshore population, and 22.7 cm TL, 1.16 yr-1 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 offshore population. Estimates of the mortality coefficients were: Z = 6.40 yr-1, M = 2.14 yr-1 and F = 4.26 yr-1 for the inshore population, and Z = 6.40 yr-1, M = 2.10 yr-1 and F = 4.30 yr-1 for the offshore population. Similar estimates of the exploitation rate (E = 0.67) were obtained for the two populations. This value exceeds the optimum (Eopt) 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 B. auritus populations. JOURNAL OF THE GHANA SCIENCE ASSOCIATION Volume 2 No. 3 (2000) pp. 113-12