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. The von Bertalanffy growth parameters, L∞, K and tₒ, were estimated as 23.0 cm T L , 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 (F = 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 D. auritus
populations.
