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Status of diversity, abundance and seasonal variations of gill net catches of cichlids in Lake Bosumtwi, Ghana


A. Asase
T.L. Lauridsen
P.O. Sanful
E.E.K. Quansah

Abstract

The cichlids in Lake Bosumtwi are under increasing pressure with a recent build-up in local fishing pressure. This study was conducted to  assess the status and seasonal catch rates of fish species using gillnets over a two-year period. Four species and one introduced fish  belonging to the Cichlidae family were encountered in the study. Coptodon discolor (Günther, 1903) was the most abundant species,  making up 75.5% of the total fish caught (100.1 kg). Tilapia busumana (Günther, 1903) was the least abundant species, representing only  0.6% of biomass. Catch per unit effort was significantly affected by seasonality; however, species diversity, richness and evenness were  not influenced by seasonal variations. The highest catch rates (975.62 g net−1 night−1) were recorded in the minor wet season (August to  November). No statistical differences were detected in the diversity indices estimated for all three seasons of study. The key physico- chemical parameters (conductivity, salinity, temperature and pH) measured were within the tolerance range for tilapia survival and  growth, with the exception of dissolved oxygen that decreased below 3 mg l−1 during the lake’s deep mixing events in August. Overall,  physico-chemical factors explained 75% of fish catches, with salinity levels correlating significantly with catch per unit effort. 

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eISSN: 1727-9364
print ISSN: 1608-5914