Comparative quantification of juvenile croakers <i>Pseudotolithus</i> species incidentally killed in coastal artisanal shrimp beam trawl fisheries off Lagos Coast, Nigeria and management implications

Abstract

The landings of coastal artisanal shrimp beam trawl fisheries operating in nearshore water of South West Nigeria were sampled to identify the length class of croakers Pseudotolithus spp. vulnerable to exploitation and to quantify the numerical and gravimetrical abundance of croakers in the by-catch compositions. The result shows that three species of juvenile croakers; Pseudotolithus elongatus, P. senegalensis and P. typus with a total length range of 4 – 30 cm constitute the by-catch species. Croakers with a total length range of 4 – 10 cm form 65% by number and were rejected and discarded ashore while croakers with a total length range of 11 – 30 cm were marketed and consumed. Percentage weight contribution of croaker family sciaenidae, from 96 replicate landings by eight (8) boats was 7.42%, target shrimps, Nematopaleamon hastatus was 85% while other 18 families of by-catch species was 7.58%. The total weight of the sciaenidae family landed was significantly (t-test; P<0.05,0.010) more than the weights of 9 other individual commercially important by-catch families. Sustainability of croakers stock through the introduction of by-catch reduction devices into the fishery to exclude croakers as primary species of significance and the effect of length class of croakers caught on other commercial fisheries targeting mature stock of croakers are discussed.


Key Words: Croakers, Shrimp Trawl, Lagos Coast.


Journal of Aquatic Sciences Vol.19(2) 2004: 77-84