THE BIOLOGY AND FISHERY OF THE SPIDER CRAB MAJA SQUINADO AROUND JERSEY (CHANNEL ISLANDS)

Currently, Maja squinado is fished commercially around Jersey and exported to southern Europe. Jersey fishermen have expressed concern that increasing levels of fishing effort are required to maintain gross catches. The present study has examined the patterns of growth, moulting, seasonal cycles (abundance, spawning), and the effect of fishing method (trap, tangle net) and fishing mortality on M. squinado, to provide management information on which to conserve this fishery. Seasonal variation in catch per unit effort (CPUE) of juvenile Maja squinado was closely correlated with seasonal cycles in seawater temperature. Juveniles were first observed in coastal nursery areas in the autumn at a size-of 20-40mm carapace length (CL). Growth and moulting, which only occurred in juvenile crabs, was restricted to the summer and autumn. Growth was rapid and a terminal moult associated with maturity, occurred after approximately 2½ years. Terminally-moulted crabs varied in size from 80mm-189mm CL (males) and 75mm-155mm CL (females). Spawning was seasonal, typically occurring between April and November. Duration of egg development was between 2-4 months and evidence from the seasonal occurrence of egg stages suggests females may spawn 2-3 times. The composition of the commercial catches of Maja squinado varies throughout the year as a result of seasonal migrations; however, catches from shallow (< 20m) areas typically contain high proportions of recently-moulted adults and juveniles, whereas catches from deeper ( > 20m) areas contain high proportions of 'hard' adults (which underwent their terminal moults in previous seasons). Differences in catch composition between these two areas arise because of a two month lag between the seasonal offshore migrations of hard and recently-moulted adults, and the location of spider crab nurseries in shallow, coastal areas. The relatively low abundance in catches of hard-shelled adults larger than the minimum legal size (MLS)(l20mm CL), and the disappearance from catches, within twelve months of their terminal moult, of most recently-moulted adults larger than the MLS, suggests that fishing mortality is high around Jersey and fishermen rely on the annual recruitment to support the following years' fishing. Tangle net catches contain higher proportions of large, morphometrically mature males and lower proportions of small, juvenile, and female crabs than trap catches.The Department of Agriculture and Fisheries, Jerse