Evaluations of nordmore grid by-catch reduction device (BRD) in nearshore shrimp beam trawl fisheries, Nigeria

Abstract

Fishinb experiments with conventional and modified codends were conducted to reduce fish bycatch from shrimp beam trawl fisheries off Lagos coast, Nigeria. The modified codend consist of Nordmore grid with a guarding panel and bar spacing of 20 mm. Simultaneous paired  comparisons against conventional codends showed that the modified codend significantly reduced the by-catch of juvenile fishes up to 72.06% (t-test, P<0.05;0.01) with no significant reduction (2.9%) in the quantity
of the target shrimps, Nematopaaemon hastatus (T-test,p:>0.05;0.01 ).small sized and fusiform shaDe fishes with total length range of 4 to 10 cm were mostly reta ined by the mod ified codend, eg. Epinephelus aenus (p>0.05;0.01 ) and pomadasys jubelini (p>0.05;0. 01) while large and flattened fish specimens with a total length range of 11 to 30 cm were mostly excluded , ego Dasyatis margaritas (p<0.05;0. 01) and Carcha rhinus brachyrus (p<0.05;0. 01). The high percentage reduction of the 3 species of most aboundance and priortised croaker by-catch family  sciaenidae ego Pseudotolithus elongates (72.73%,p<0.05;0.01), p. senegalensis · (66 .65%,p<0.05.01) and P. typus (6 8.33,p<0.05;0.01) makes the BRD a conservation tool for commercial application. The potential of Nordmore grid to alleviate by-catch problem and its limitation in a developing economy is discussed.

Keywords: By-catch reduction device, Shrimp, Trawl fisheries, Nigeria