Assessment of minimum landing sizes of the edible crab, Cancer pagurus L., on the east coast of England

Abstract

In 1986, the minimum landing size (MLS) of edible crab ( Cancer pagurus L.) was increased on the south coast of England and Wales from 115 mm carapace width (CW) to varying sizes of up to 160 mm CW depending on district. The MLS remained at 115 mm on the east coast of England. Fisheries in this area are likely to come under increasing pressure as they provide alternative early season supplies to the European continental market. For this reason, a reassessment of crab MLS from Norfolk to the Scottish border of Northumberland has been undertaken using length cohort analysis. Increasing the MLS would result in increases in both yield-per-recruit ( Y/R) and particularly biomass-per-recruit ( B/R) in all of the three main fisheries. Fishing mortality was highest in Norfolk where the mean size of crabs landed is low. Large increases in Y/R and B/R, preceded by considerable short-term losses, were predicted therefore for Norfolk, but emigration of mature females, the physical nature of the substrate, and possible density-dependent effects may limit the benefits. Two additional factors suggest that the overall gains and losses may be underestimates. Firstly, the introduction to the model of a stock-recruitment relationship predicts that much larger gains in long-term yield and stock biomass may accrue from an increase in MLS. Secondly, fishermen in Yorkshire obtain a lower price for crabs between 115 and 127 mm CW than for those over 127 mm, and when these prices are included in the model, the initial losses in revenue following an increase in MLS are less and the expected long-term gains are greater than the Y/R prediction. This assessment highlights the need for further studies on growth, maturity, fecundity and recruitment of Cancer pagurus.