Comparing the size selectivity and exploitation patterns of two T0 codends with T90 codends in demersal trawl fishery targeting white croaker (Pennahia argentata) of the northern South China Sea

The size selectivity and exploitation patterns of two T0 (diamond mesh) codends were tested and compared with T90 (diamond mesh turned by 90°) codends in demersal trawl fishery targeting white croaker (Pennahia argentata) of the northern South China Sea. The four experimental codends involved two mesh sizes, 30 and 35 mm, respectively. The size selectivity of the T0 codend with mesh size of 30 mm, T0_30, was used as a starting point to compare with the rest codends. The results showed that compared with the T0_30 codend increasing the mesh size to 35 mm or applying the T90 codends would result in significantly larger L50 values, and the retention risk (probability) of undersized white croaker with length < 8.5 cm would significantly reduce. These codends, however, had no effect on improving the size selectivity of undersized white croaker with the length ranging between 10 and 15 cm. The results of our study will have relevant implications for fishing gears management and future direction of codend selectivity research.