桁杆虾拖网捕捞脊腹褐虾网囊网目选择性试验

Selectivity experiment on the cod-end mesh of beam shrimp trawl for catching Crangon affinis

采用套网试验法在长江口渔场对25 mm桁杆虾拖网网囊网目的选择性进行了试验。结果表明：当网囊网目内径为25 mm时,网囊与套网内脊腹褐虾的体长范围在30~80 mm之间,其中网囊内虾的优势体长在46~70 mm之间,套网内虾的优势体长在41~60 mm之间;50%选择体长L0.5为50.53 mm,选择范围SR为9.86 mm;逃逸虾的平均存活率为96.25%。

By means of using the cover net experiment method,the selectivity of cod-end mesh with 25 mm of beam shrimp trawl has been tested on the Yangtze Estuary fishing ground.It came to the conclusions that when the cod-end mesh size is 25 mm,the range of body length of Japanese sand shrimp（Crangon affinis de Haan） is 30-80 mm between cover net and cod-end,in which the dominant body length was ranged from 46 mm to 70 mm in cod-end and from 41 mm to 60 mm in cover net.The fifty percent of selective length was 50.33 mm and the selectivity range（SR） was 9.86 mm.The average survival ratio of escaped shrimp was 96.25%.