175 



170 



165 



160 



155 



150 



145 



65 



64 



63 



62 M 



61 



60 



59 



58 | 



57 IJ 



56 



55 



54 



o 



PRINCE WILLIAM 

 SOUND 



ST. MATTHEW 



BERING SEA 



GULF OF 

 RLflSKfl 



PRIBILOF IS 



DLGA BAY 



65 

 64 

 63 

 62 

 61 

 60 

 59 

 58 

 57 

 56 

 55 

 54 



175 170 165 160 155 150 145 



FIGURE 1.— Locations of the four blue king crab populations: St. Matthew Island, Pribilof Islands, Olga Bay, and Prince William Sound. 



evaluating the fitted equation to find the size corres- 

 ponding to 50% maturity. Variance of SM50 was es- 

 timated using the technique described in Somerton 

 (1980a). Estimates of SM50, standard deviations, 

 and 95% confidence intervals are shown in Table 1. 



TABLE 1.— Female size at 50% maturity (SM50), standard devia- 

 tion, and 95% confidence intervals for each of the four blue king crab 

 populations studied. 



Male Size at Maturity 



Male blue king crab do not display external features 

 that unambiguously indicate maturity; however, at 

 maturity the growth of the major chela may increase 

 relative to the growth of the carapace. Although this 

 relationship has not been established for blue king 



crab, for tanner crab, Chionoecetes bairdi, the size of 

 maturity based on chela allometry was almost identi- 

 cal to that based on a change in reproductive tract 

 weights (Brown and Powell 1972). If this is also true 

 for blue king crab, then the size at maturity can be es- 

 timated by the size at which chela growth in- 

 creases. 



When chela measurements are plotted against car- 

 apace measurements on log-log axes, the data 

 assume a pattern consisting of two straight lines. 

 These lines describe the juvenile and adult phases of 

 relative growth (Hartnoll 1978). For some species of 

 crab, especially brachyuran crabs, the two lines have 

 similar slopes but different intercepts. Somerton 

 (1980a) described a technique for estimating the size 

 of maturity for species with this pattern of relative 

 growth. For other species, including blue king crab, 

 the two lines have different slopes and intersect at 

 the size at maturity. In this case, the problem of es- 

 timating the size at maturity is one of estimating the 

 intersection point of the two phase lines. 



The intersection point can be estimated from 

 morphometric data by finding the best fit of a model 



622 



