Selectivity of traps for the deep-water crab, Cancer johngarthi Carvacho, 1989 in the Northern Mexican Pacific

Nine crab-trap lines were set off the west coast of Baja California Sur, Mexico, from June 2000 to May 2001. Traps were of different types: conic, rectangular, and rhombic. We analysed the efficiency of the traps for Cancer johngarthi, a crab species that represents between 80 and 99% of total crab catch at locations ranging from 100 to 530 m deep. Other fauna (14 species) was scarce. The catch of C. johngarthi consisted of males with a carapace width (CW) > 125 mm and, depending on the trap type, relative abundance values from 0.05 to 1.2 crabs per trap-hour. According to the catchper-unit-effort for gender and size, the most efficient type of traps were the conic ones, whereas rhombic traps were the least efficient. The sizes at first catch for females were 109, 101, and 86 mm CW for conic, rectangular, and rhombic types, respectively. For males the values were 136, 134, and 78 mm CW. Though the existence of C. johngarthi was known, this is the first report of experimental fishing targeting this species. Preliminary results suggest that management strategies will be heavily dependent on taking into account the observed variability in catch effectiveness of the various traps. The use of different traps will facilitate the manager's decision regarding sizes and catch rates.