Seasonal variations in shrimp, nematopalaemon hastatus and bycatch compositions from coastal artisanal shrimp beam trawl fisheries off Lagos coast and management implications

Abstract

Wet and dry season variations in shrimps and bycatch compositions were surveyed in the artisanal beam trawl shrimp fisheries operating in near shore water (<20m depth and <2 nautical miles) in South West Nigeria. Significant variabilities in targets shrimp Nematopalaemon hastatus and bycatch compositions were detected at these temporal scales; shrimps – bycatch ratio of 14:1 and 6:1 were obtained respectively at both wet and dry seasons. The total quantity of shrimps and bycatch landings combined were more in wet season (9749.22kg) than in dry season (4090.71kg), T-test comparison was significant (P<0,05). Twenty five (25) species belonging to 20 families of fishes constitutes the bycatch species and are juveniles with a total length range of 4 to 30cm. While majority of the bycatch species occurs throughout the year, few have seasonal occurrence; Arius latiscutatus, Eretmochellys, Imbrica, Callinectes amnicola in wet season and Sardinella aurita, Chloroscumbrus chrysurus and Pseudotolithus typus in dry season. The results are discussed in terms of; (i) The rational for the introduction of management options such as seasonal closures or otherwise technological changes in gear design to sustain the coastal fishery resources, (ii) The contrast shrimp – bycatch ratio in this fishery.



Keywords: Seasonal variations, bycatch, coastal, shrimp trawl, Nigeria

AJAZEB Vol. 6 2004: pp. 1-5