Performance Evaluation of Hard and Soft Square Mesh Windows for Reducing the Juveniles in the Shrimp Trawl

Abstract- During the last few decades, the stocks of many Indian marine fish species were declined. Inserting by-catch reduction devices widely used in temperate countries fisheries as excluding devices for juvenile fish. The present study have focused on improving the escape of juveniles from shrimp trawl nets. Square mesh windows (SMWs) spacing 25 mm bar length hard and soft windows ,30mm bar length hard and soft wind ,35mm bar length hard and soft windows were tested in sea trials during September–December 2018. Field experiments were conducted on-board research vessel M. F. B. Matsyakumari-II .The cod-end mesh size used for the study was 25mm square mesh. The trawl was modified by inserting six SMWs measuring 50×50cm, three hard and three soft SMWs. The first pair of square mesh windows (25 mm H&S) were laced to the top panel of the trawl net at 1m distance from the tip of the cod end. Second pair of windows (35 mm-H &S) were fixed at a distance of 3.6 m from tip of cod end. Third pair of windows (30 mm-H&S) were fixed at a distance 6m from the tip of cod end. On the basis of weight (kg)the overall exclusion percentage was 35mm-H(5.19%) >35mm-S (4.45%) >25mm-H(3.61%) > 25mm-S (2.81%) >30mm-H (2.11%) > 30mm-S (2.07%).On the basis of Numbers (S) the overall exclusion percentage was 35mm-H (16.59%) > 25mm-H(11.89%) > 35mm- S (10.55%) > 30mm-H (7.45%) > 25mm-S (6.69 %) > 30mm-S (4.77%).SIMPER analysis showed that average dissimilarity among the 25mm-H and S SMWs was 59.48, with Oratosquilla nepa and Alepes klenii contributing the most. Oratosquilla nepa and Alepes djedaba were the species that contributed the most to the dissimilarity (63.84) in the 30mm-H &S, SMWs, whereas Oratosquilla nepa and Stolephorus commersoni were the major species that contributed to the dissimilarity (73.69) among the 35mm H &S, SMWs. The average dissimilarities between the different SMWs and codend were contributed by Fennerpenaeus indicus and Charybdis lucifera in all the cases. Differences in mean catch weight (kg) (±SE) between the codend and SMWs was 35mm-H (1.69±0.17) > 35mm-S (1.44±0.167) > 25mm–H (1.17±0.083) > 25mm-S(0.91±0.08) > 30mm-H (0.68±0.06),30mm–S (0.67±0.05) and also total number of species(S) in the codend 71 catch mean was 194.6. The mean rank of (25 mm-H (mean)=96 ;25mm-S (mean) =54.5 ; 30 mm-H (mean) =57.5; 30mm-S (mean)= 34 and 35mm-H (mean) 134;35mm-S( mean)=74.5.The implications of the results are discussed and concluded that Hard square mesh windows can be effective BRD for improving the escapement chances in the trawl nets, and the position of the window also influenced by escapement of the juveniles. But the position of the 25mm-H & S and 35mm –H &S were fixed in distal region of the codend and there was escapement of juveniles’ percentage is high.