Behavioral responses of the snow crab Chionoecetes spp. to the groundrope of a bottom trawl

Abstract

To understand the capture process of the snow crabs Chionoecetes opilio and C. japonicus to the groundrope of a survey trawl net, observations with an underwater video camera were conducted in Pacific coastal waters of northern Japan at depths ranging between 440 m and 700 m in June of both 2000 and 2001 with R/V Wakatakamaru (692 T, 1471 kW). The underwater video camera was attached at the center of the headrope of the survey trawl net to observe crab behavior toward the groundrope. A total of 466 crabs were observed. Ninety-four percent of crabs observed did not respond when the groundrope approached the crabs. Therefore, the handropes and the legs of the trawl net do not herd the snow crabs. The crabs that were not captured escaped under the groundrope. The groundrope has an important effect on the catch of snow crabs.