Handling time and predation behaviour by the crab, Cancer pagurus, preying on cultured scallop, Pecten maximus

摘要

We investigated handling time, persistence time and shell-breaking techniques by crab, Cancer pagurus (L) (13-15 cm carapace width), offered cultured scallops, Pecten maximus (L). within the recommended release size for bottom culture. Three shell height groups were used: 50-55, 60-65 and 70-75 mm. The results showed that the crabs managed to open scallops from all the three size groups. The median handling time in the 50-55 mm group (788 s) was significantly different from the median handling time of the 60-65 mm (2482 s) and 70-75 turn (2980 s) groups. The median persistence time increased significantly with each scallop size, from 89 s in the 50-55 mm group to 97 s in the 60-65 mm and 125 s in the 70-75 mm group. We observed a change in the shell-breaking techniques from a dominance of smashed scallops in the 50-55 mm group to more punched and chipped scallops in the 60-65 and 70-75 mm groups. The shift in predation behaviour when crabs were offered 50-55 mm scallops compared with the larger groups is discussed in relation to strategies in the release of scallops to seabed cultures.