日本蟳入笼行为及其地笼网逃逸口选择性的实验研究

Ingress behavior and escape vent selectivity of Charybdis japonica in the cage net

选取蟳山东沿海捕获的体质健壮日本(Charybdis japonica),在实验室水槽内暂养1周后开展相关实验。观察蟳光照、诱饵条件对日本入笼行为的影响。结果表明,蟳日本畏光,在明亮条件下大多数分布于养殖水槽的四角,在黑暗条件下趋向随机分布,蟳遮黑处理和放置诱饵均能增加日本的入笼比例;在地笼网底部设置尺寸(长×高)分别为4 cm×3 cm、4.5 cm×3 cm、5 cm×3 cm、5.5 cm×3 cm的长方形逃逸口时,蟳日本50%选择甲长(L50)分别为3.75cm、4.24 cm、4.54 cm、5.08 cm,选择范围(SR)分别为0.65 cm、0.45 cm、0.62 cm、0.82 cm;L50与逃逸口长度呈线性相关关系,约为逃逸口长度的92.3%。根据实验结果,蟳结合日本最小性成熟甲长和市场最小可接受规格,综合分析认为,地笼网逃逸口最适尺寸(长×高)为4.3 cm×3 cm。本研究旨在为有效保护日本蟳幼蟹资源提供技术依据。

To improve the selectivity of cage nets and protect juvenile crab resources, effect of cage-net escape vent size on selecting Charybdis japonica was evaluated. At the same time, the impact of illumination and bait on the behaviour of C. japonica was observed. C. japonica were photophobic： under bright conditions they preferred to be in the four comers of the water tank. Under dark conditions, they were randomly distributed. Both bait and the colour of black entice C. japonica into the cage. The rectangular escape vents at the bottom of the cage net were 4 cmx3 cm, 4.5 cmx3 cm, 5 cmx3 cm and 5.5 cmx3 cm length by height, which corresponded to L50 （the corresponding carapace length with 50% retention） of C. japonica being 3.75 cm, 4.24 cm, 4.54 cm and 5.08 cm, respectively, and SR （the selection range） being 0.65 cm, 0.45 cm, 0.62 cm and 0.82 cm, respectively. Ls0 has a linear relationship with the length of the escape vent, being about 92.3% of its length. Based on the minimum carapace length of sexually mature C. japonica, the minimum market-acceptable size standard and the experimen- tal results, we conclude that the most appropriate size （lengthxheight） of the escape vent is 4.3 cmx3 cm.