Exploitation rates and management implications for the fisheries of Bontanga reservoir in the Northern Region of Ghana

Abstract

The exploitation rates of eight major component fishery species, Auchenoglaris accidentali, Brycianus nurse, Clarias gariepinus, Hemichromis fasciatus, Marcusenuis, Oreochromis niloticus, Sarotherodon galilaeus and Tilapia zillii, of gill net fishery of Bontanga reserviour, were studied from March, 2004 to March, 2006 based on length-based models. The exploitation rates (E) of A. accidentalis and H. fasciatus were 0.7 and 0.6 which exceeded the optimization (Bopt0 criterian of 0.5 for sustainable exploitation of fisheries, indicating that these species were over exploited. For B.nurse and S. galitaeus, E=0.5, indicting that these species were at their maximum rates of exploitation. For C. gariepinus, M. Senegalensis, O. niloticus and T. zillii, E<0.5, indicating that these species were not over exploited. Based on the selection factor of the legal minimum gill net mesh size of 5 cm of Ghana fisheries Act 625, the estimated mesh size for catching the eight species ranged from 9.9-19.3 cm, calling for an upward review of the legal minimum mesh size of gill nets from 5 to 10 cm for sustainable exploitation of reservoir fisheries. The adoption of minimum mesh size of gill nests of 10 cm, restriction of further entry into the fishery, control rights and community based co-management system are some management option-suggested to enhance sustainable exploitation and management of the fisheries.