Abundance and distribution of two blue crabs Callinectes amnicola and C. pallidus in the Volta Estuary of Ghana

Abstract

The abundance and distribution of two blue crab species along the main channel of the Volta estuary, Ghana was studied from October 2015 to September 2016. A total of 2623 crabs were caught comprising 1535 Callinectes amnicola and 1088 C. pallidus. The percent contribution by weight to the total catch was 70% and 30% for C. amnicola and C. pallidus respectively. C. amnicola exhibited differential sex distribution with more females (739) concentrated within 3 km from the mouth of the estuary than males (661). Males dominated catches beyond 3 km (110) as against females (25). Both sexes of C. pallidus were concentrated within 3 km from the sea and dominated catches during periods of high salinity (>10‰). Distribution of the blue crabs was influenced by changes in salinity levels (5-33‰) and the tidal regime (1.29-1.69 m). For sustainable exploitation, trapping should be beyond the 3 km distance from the mouth of the estuary at high tide.