to their departure from the shallow (<35 m) sam- 

 pling depths in 1984 still had full clutches of eyed 

 eggs, liberation of a large proportion of larvae in 

 shallow water may enhance chances for larval sur- 

 vival overall. At the time of the migration, bottom 

 temperatures in Bonne Bay at depths beyond 35 m 

 are probably 0°C or lower [deep water temperatures 

 are not available for Bonne Bay but Squires et al. 

 (1971) reported temperatures <0°C at depths 

 beyond 30 m in early June in North Arm, Bay of 

 Islands, about 40 km to the south]. Release of lar- 

 vae in shallow, warmer water (temperature was 3°C 

 at 30 m during 7-11 May) would considerably reduce 

 the degree of thermal shock associated with larvae 

 swimming to the surface. The rate of embryonic 

 development would likely be increased also, result- 

 ing in earlier larval release. 



In the development of a management strategy for 

 C. opilio stocks on the Atlantic coast of Canada, a 

 key assumption has been that, despite high levels 

 of exploitation, reproductive potential in a stock re- 

 mains at prefishery levels. The basis for the assump- 

 tion is that females are protected from exploitation 

 by the 95 mm CW minimum legal size because they 

 do not grow to that size and also that males mature 



at sizes much smaller than 95 mm CW. In a recent 

 review, following more than 15 yr of heavy fishing 

 in some areas, there was no evidence to indicate that 

 the assumption was invalid (Elner and Robichaud 

 1983). However, the observations presented here 

 suggest that a large size differential between the 

 male and female of a pair is an important element 

 of behavioral interactions during breeding activity. 

 It is possible that males smaller than 89 mm CW 

 (the smallest male observed paired with a female), 

 even though physiologically mature, may be less like- 

 ly to mate successfully in competition with large 

 males. 



Males and females appear to be segregated over 

 most of the year (Hooper in press). Observations on 

 the east coast of Newfoundland indicate that large 

 males occur mainly on muddy bottom in deep water 

 whereas females and small males occur on sand- 

 gravel or rocky bottom somewhat shallower (Miller 

 and O'Keefe 1981). In the breeding migration which 

 occurs in Bonne Bay, Hooper (in press) suggested 

 that males leave the deeper water area after select- 

 ing a mature female which is carried to the shallow 

 water breeding area. Males retain possession of in- 

 dividual females for extended periods (Hooper in 



86 

 84 

 82 

 80 



1 78 



=: 76 



t— 

 o 



» 74 



2 72 



4 

 CC 



S 70 



UJ 



^ 68 



UJ 



u. 



66 



64 

 62 

 60 

 58 



92 94 96 98 100 102 104 106 108 110 112 114 116 118 120 122 124 126 128 130 132 134 136 138 140 



MALE CARAPACE WIDTH (mm) 



Figure 2— Recession of female carapace width on male carapace width for pairs of Chionoecetes opilio collected in Bonne Bay, New- 

 foundland, during April-May 1984. Numbers adjacent to points indicate more than one observation. Slope of the regression is not signifi- 

 cant (P = 0.017). 



709 



