DOES INTENSE FISHING ON MALES IMPAIR MATING SUCCESS OF FEMALE DUNGENESS CRABS

Commercial capture of female Dungeness crabs, Cancer magister, is proh ibited and minimum size limits for commercial harvest of male crabs ar e designed to allow most males to mate at least once before capture. A nnual exploitation rates of ten exceed 90%, however, and the resulting scarcity of large males might reduce mating success among large femal es. We present new data regarding (i) sizes of male and female crabs c ollected in premating embraces, (ii) carapace width frequencies of fem ale Dungeness crabs, (iii) presence of sperm plugs and sperm, and (iv) fecundity. Minimum carapace width of hard-shelled mating males typica lly exceeds postmolt carapace width of soft-shelled females (i), but f emale Dungeness crabs exceeding the minimum legal size of males usuall y account for less than 5% of mature adult female crabs (ii), and subl egal-sized males actively participate in mating (i). Remnants of sperm plugs, definitive indicators of mating, were found in 97.5% of recent ly molted large females (iii), suggesting that virtually all molting f emales mate regardless of size. On the basis of (ii) and (iv), hypothe tical worst-case calculations, assuming that no large females could fi nd mates, suggest that total egg production would be reduced by no mor e than 2-25% among molting female crabs.