Growth per molt of male snow crab Chionoecetes opilio from Conception and Bonavista Bays, Newfoundland

Over 6000 male snow crabs were tagged during a 6-year period in Conception Bay, Newfoundland, in order to estimate the increase in size at the time of molting. Ninety-two animals were recaptured which had usable information on growth increments. Based on the amount of growth, we hypothesized that 20 of these had molted once while the remainder molted twice. Two lines of evidence support this interpretation. First, animals in the group presumed to have molted twice were at liberty on average twice as long as those presumed to have molted once. Second, a regression line fitted to data on single-molters predicted the size after two molts in close agreement with a regression line fitted to data on double-molters. A nonlinear regression model was developed to estimate the parameters of the relationship between post- and pre-molt sizes using the combined data set for single and double molters. The method was also generalized to account for a quadratic relationship between post- and pre-molt size. For crabs in the size range 80-110 mm carapace width, the predicted size after molting in mm is equal to 7.398 + 1.038 x pre-molt size. A similar study conducted in Bonavista Bay, Newfoundland, yielded growth information for 18 animals. The molt increments appear similar to those observed from Conception Bay.