Codend Mesh Selectivity of Trawl in the Eastern Waters at Hainan Island
In order to support the implementation and management of"National Marine Fishing Gear Cata-logue",a selective test of five diamond mesh sizes of 25 mm(control group),30 mm,35 mm,40 mm and 45 mm was carried out in trawlers in April 2022 by using the combined operation method in the eastern waters at Hainan Island(E 110°39′-111 ° 12′,N 19°01′-19°33′).The selective analysis of 4 mesh sizes was carried out by using logistic curve and maximum likelihood estimation method.The results showed that the 50％selection of body length(L50)was 94.6 mm,104.5 mm,125.0 mm and 143.0 mm for Sauri-da tumbil at mesh size of 30 mm,35 mm,40 mm and 45 mm,with selection range of 22.2 mm,34.4 mm,23.2 mm and 26.1 mm.The L50 for Trachinocephalus myops was 86.1 mm,96.1 mm and 115.2 mm,cor-responding selection range of 29.4 mm,20.0 mm and 27.0 mm;the L50 for Polynemus sextarius was 65.9 mm,73.8 mm,89.6 mm and 103.1 mm,corresponding selection range of 9.2 mm,18.0 mm,24.2 mm and 21.2 mm;the L50 for Upeneus bensasi was 82.6 mm,89.5 mm and 100.0 mm,corresponding selection range of 28.8 mm,26.3 mm and 33.5 mm.The relationship between codend mesh size of S.tumbil,T.myops,P.sextarius,and U.bensasi and L50 was expressed as:Me=0.2959L50+2.952(r2=0.9829),Me=0.3325 L50+2.040(r2=0.9685),Me=0.3861 L50+5.403(r2=0.9842)and Me=0.5681 L50-16.517(r2=0.9865),respectively,the minimum mesh size of 43.9 mm in S.tumbil,59.5 mm in T.myops,58.5 mm in P.sextarius,and 33.2 mm in U.bensasi.In conclusion,the suitable mesh size of trawl codend should be 43.9 mm.
万方数据
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