Asian Horseshoe Crab Bycatch in Intertidal Zones of the Northern Beibu Gulf:Suggestions for Conservation Management

Bycatch poses a severe challenge to global fishery management.Although studies have focused on marine megafauna bycatch,research on relevant issues regarding invertebrates is limited,particularly for the threatened horseshoe crabs.In this study,the distribution of fishing gears and the bycatch intensity of Asian horseshoe crabs in the intertidal zones of the northern Beibu Gulf that harbors the most abundant juvenile Asian horseshoe crabs populations in China were evaluated.Seven intertidal nursery habitats for Tachypleus tridentatus and Carcinoscorpius rotundicauda were surveyed from May to July in 2021.A transect that crossed the tidal creeks and tidal flats between the high tide embankment/vegetation and low tide line of a given habitat was surveyed during the ebb tides.The type,number,and GPS of fishing gears were recorded when sighted,and the number and prosomal width of each horseshoe crab species were measured.Bycatch intensities differed among habitats,ranging from 0.3 to 18.4 and 1.2 to 22.7 individuals per kilometer of transect for T.tridentatus and C.rotundicauda,respectively.Among the three identified fishing gear types,ground cages and stick net sets caused a stronger bycatch pressure on these two species.Most T.tridentatus bycatch and C.rotundicauda bycatch were large individuals in late juvenile and adult stages.Therefore,the ground cages and stick net sets along/near the tidal creeks,mangrove fringe,and low tide line should be regulated and removed to ensure the functionality of the intertidal zone as the spawning corridor and nursery habitat of Asian horseshoe crabs.