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Earl E. Krygier 

 William G. Pearcy 



School of Oceanography 

 Oregon State University 

 Corvallis, OR 97331 



LENGTH-WIDTH-WEIGHT RELATIONSHIPS 



FOR MATURE MALE SNOW CRAB, 



CHIONOCOETES BAIRDI 



Snow crabs have been exploited commercially in 

 Alaska since 1961 (Alaska Department of Fish 



and Game 1975). Chionocoetes bairdi is the pre- 

 dominant species with C. opilio composing up to 

 25% of the catch from the Bering Sea. Landings 

 were small and intermittent in the early 1960's 

 but increased to about 3.2 million lb in 1968. Land- 

 ings expanded dramatically thereafter and ex- 

 ceeded 60 million lb in 1974, with an ex-vessel 

 value of more than $12 million. 



Carapace width measurements have been col- 

 lected from the commercial snow crab catch by 

 biologists since the inception of the fishery; indi- 

 vidual weights, however, are not routinely col- 

 lected because the task is rather time-consuming. 

 The relationships between carapace width, 

 length, and body weight are of interest to 

 biologists and processors. The relationship be- 

 tween carapace length and width is of interest be- 

 cause the carapace shape is one of the diagnostic 

 characteristics to distinguish between C. bairdi 

 and C. opilio and hybrids of the two species (Kari- 

 nen and Hoopes 1971). The relationships between 

 carapace width and weight and carapace length 

 and weight have many uses. They are, for exam- 

 ple, indicators of condition, used to calculate 

 biomass, and used to estimate recovery of edible 

 meat from crabs of various sizes. 



Materials and Methods 



Carapace length and width and body weight 

 measurements were taken from 240 mature male 

 C. bairdi from commercial catches made south of 

 the Alaska Peninsula in the vicinity of the 

 Shumagin Islands in May 1975. Length and width 

 measurements were taken to the nearest millime- 

 ter with vernier calipers and weights were re- 

 corded to the nearest gram. Length was measured 

 from the posterior medial edge of the carapace to 

 the anterior medial point of the right orbit. The 

 rostrum was not included in the length measure- 

 ment because it often erodes when crabs are car- 

 ried in the live tank of fishing vessels. Width was 

 measured at the widest part of the carapace and 

 included the lateral branchial spine. Width 

 ranged from 128 to 185 mm, weights from 635 to 

 2,230 g, and lengths from 92 to 143 mm. 



The basic linear regression formula W = a + bL 

 was used to express the relationship between 

 width (W) and length (L). Weight ( Wt) was related 

 to width and length by the power functions, log 10 

 Wt = log 10 a + b log 10 W and log 10 Wt = log 10 a + b 

 log 10 L. The constants a and b were determined 

 empirically. 



870 



