The effect of cooking and freezing on the carapace length of the American lobster, Homarus americanus H. Milne Edwards, 1837

Abstract

In the southern Gulf of St. Lawrence, there were concerns that freezing seized American lobster (Homarus americanus) to preserve evidence for the court could potentially reduce the carapace length, and compromise the enforcement of a fishery regulation limiting minimal legal size. Tests were performed on 30 soft-and 30 hardshell American lobsters to study the potential for shrinkage when lobsters were cooked and/or frozen. It was found that carapace length reduction was related to the carapace condition. Except for freezing of soft-shell lobsters, all treatments produced a statistically detectable reduction in carapace length. However, the average carapace length reduction ranged from only 0.1-0.5 mm, the highest increase being for hard-shell lobsters after cooking, freezing then thawing (t-test, P-value=1.8×10-10). Out of the 60 animals studied, none had a carapace length reduction over 0.7 mm, while four had a carapace length increase. Although a carapace length reduction could be detected statistically, this should not cause problems in enforcing a minimum legal size.

Influence of cooking, refrigeration, and freezing on size of blue swimmer crabs, Portunus pelagicus (Linnaeus, 1758)

“…Ibbott et al (2001) found that cooking had no statistically detectable effect on the carapace length of the rock lobster, Jasus edwardsii (Hutton, 1875) noting that discrepancies between repeated measurements were due to measurement error and the difficulty in measuring live animals. More recently, Mallet (2003) andMelville Smith &Thomson (2003) studied shrinkage in the lobsters, Homarus americanus H. Milne Edwards, 1837 and Panulirus cygnus George, 1962, respectively, and found that these species decreased in size marginally as a result of cooking and freezing. In the case of crabs, Williams & Lee (1980) have reported the effects of cooking and freezing on the size of the mud crab, Scylla serrata (Forskål, 1775), and found that neither process affected the size of the rigid exoskeleton.…”