Mating of snow crab Chionoecetes opilio (O. Fabricius, 1788) (Decapoda, Majidae) in the fjord of Bonne Bay, Newfoundland

Pairs of male and female snow crabs, Chionoecetes opilio, in mating courtsh ip embrace were collected by SCUBA diving between 1984 and 1991, and with t angle nets between 1987 and 1993 in the Bonne Bay fjord, Newfoundland. A Ne phrops trawl was also used to study the snow crab population size structure between 1988 and 1993. Males in mating courtship embrace were all identifi ed as hard-shell morphometrically mature. Although large hard-shell juvenil e males were present in the population, they did not participate in the rep roduction. Comparison of the size structure of males in mating pairs and in the population also show that small mature male crabs can be excluded from mating by larger dominant mature males. The size structure between females in mating pairs and in the population was not significantly different. A d epth segregation by size on the very steep slope of the fjord was observed for male snow crabs in mating pairs, as smaller males were found above 50 m . There was no correlation between male and female size in mating couples, but males were always larger than females. We conclude that there is a stro ng intra-specific competition between males during mating in nature.