MORPHOMETRY AND MATURITY OF PAIRED TANNER CRABS, CHIONOECETES-BAIRDI,FROM SHALLOWWATER AND DEEP-WATER ENVIRONMENTS

Paired male and female Tanner crabs, Chionoecetes bairdi, in a premati ng embrace were collected from shallow-(<13 m) and deepwater (>150 m) benthic environments by scuba and submersible, respectively. Pubescent females were restricted to shallow water; males grasping them were si gnificantly smaller than those grasping oldshell multiparous females w ith eyed embryos in a large, deepwater mating aggregation. Males appea red to select for large sizes among pubescent females, but not among m ultiparous females, which were limited in size range. Grasping males w ere 82.6-166.2 mm carapace width (CW) (xBAR = 114.8) and represented a t least three different width frequency modes; all were larger than th eir female partners. Paired females represented two modes with mean CW almost-equal-to 77 mm for pubescent and 99 mm for multiparous individ uals. Only one to three of 176 male graspers were small-clawed (morpho metrically immature), a statistically nonsignificant proportion; sever al others had partially regenerated claws but were otherwise morphomet rically mature, as evidenced by the second right merus. These data sup port the hypothesis that the attainment of morphometric maturity, evid enced by a relatively large chela to body size ratio, is a prerequisit e for functional maturity, the ability to mate competitively in wild p opulations.