GROWTH OF THE ADULT MALE KING CRAB 



69 



raatical functions. At present, however, the com- 

 plexity of interdependence of growth, mortality, 

 and i-ecniitment precludes the mathematical for- 

 mulation of a growth parameter which is suit- 

 able for analytical purposes. Either elimination 

 or determination of the interaction of mortality 

 and reci-uitment on our data must be resolved first ; 

 for prediction of yield under varying conditions 

 reqidres that each parameter be independent or in 

 terms of coefficients which represent the magni- 

 tude of their integrated effect. Also, the growth 

 rate presented represents the average growth of 

 the population by lengths and would, for the pur- 

 pose of calculating yields, be more meaningful if 

 presented in terms of weights. The king crab's 

 live weight is, however, not verj' significant, since 

 meat-weight is subject to wide variation for any 

 one size, while body-weight remains essentially 

 constant. Therefore, it seems more appropriate to 

 discuss growth by weights and resulting yield in a 

 study of productivity. 



It would be desirable to compare the growth 

 curves developed in this paper with those of 

 Marukawa (1933), Nakazawa (1912), and Wang 

 (1937), presented earlier. The Marukawa and 

 Wang growth curves are based on size intervals 

 between modes and progression of modes in size- 

 frequency distributions which would tend to re- 

 flect the growth of only molting crabs. Xakazawa 

 bases his curve on growth increment per molt 

 and frequency of molt which he assumes occurs 

 at least once a year. Thus, his cur\'e would also 

 reflect primarily the growth of only molting crabs. 

 The curv'es developed in our paper, on the other 

 hand, are weighted by the proportion of each size 

 that does not molt and for the larger sizes par- 

 ticularly will show a slower growth rate. There- 

 fore, the cur\'es developed by the authors cited 

 and those described in this report are not directly 

 comparable. 



Considering the rate of growth concerning juve- 

 nile crabs, as shown by the data of the above in- 

 vestigations and our obsen-ations in Unalaska 

 Bay, we speculate that an 80-mm. crab {N—2) in 

 the eastern Bering Sea may be about 4 years old. 

 We hesitate, however, to place a precise estimate 

 of size and corresponding age on our N values 

 until the present juvenile crab studies are further 

 advanced. 



SUMMARY 



During the 6 years (1954-59) the U.S. Fish and 

 AVildlife Service has carried on a study of the 

 southeastern Bering Sea king crab Paralithodes 

 camtscha-tica. One phase of the investigations 

 has been to estimate the rate of growth of the 

 adult male king crab. 



Estimating the growth rate required the use of 

 three factors: (1) group progression in size-fre- 

 quency distribution; (2) growth increment per 

 molt; and (3) the proportion of each size molting 

 in any given year. 



Obsenations of size group advancement through 

 5 years of size-frequency distribution samples af- 

 forded an estimate of the growth rate for the 

 smaller adult crabs. Eesults show that a size 

 group of crabs averaging 81 mm. in carapace 

 length attains a length of 126 mm. after three 

 years — an annual growth increment of 15 mm. 



Tagged crabs measured at release and again at 

 recovery provided data indicating that the growth 

 per molt is approximately 16 mm. for all crabs 

 more than 110 mm. in length. The proportion 

 molting for each size was calculated from observa- 

 tions on shell condition reported during each year 

 of the station-pattern sampling program. By 

 combining growth per molt and the proportion 

 molting, the average annual growth increment of 

 crabs greater than 110-mm. carapace length is cal- 

 culated. The resixlting curves for each year of 

 sampling exhibited a rapidly decreasing average 

 annual growth increment as the crabs increase in 

 size. 



The growth rate of crabs, greater than 110 mm. 

 in length, was estimated by employing a model 

 which represents the progression of a year class 

 through time for each of the years 1956-59. 



The growth rates as estimated from size-group 

 progression and the model method were combined. 

 The resulting growth curves calculated from the 

 1956, 1958, and 1959 data were quite similar, and 

 showed that on the average, male crabs 80 mm. in 

 carapace length will attain a length of 168 nmi. 

 after 8 yeai-s of growth. Crabs growing at the 

 rate depicted for 1957 would be 153 mm. in length 

 at the end of an equal period. The reduced 

 growth rate for 1957 was due primarily to the 

 lower frequency of molting recorded in the 110 

 to 150 mm. sizes. 



