GROWTH OF THE ADULT MALE KING CRAB PARALITHODES CAMTSCHATICA 



(TILESIUS) 



By Douglas D. Weber and Takashi Miyahaka 

 Fishery Research Biologists, BUREAU OF COMMERCIAL FISHERIES 



A request for study of the southeastern Bering 

 Sea king crab {ParalitJwdes camtschatica 

 (Tilesius)) stock was made to the International 

 Xorth Pacific Fisheries Commission by the United 

 States Government in February 1954 in accord- 

 ance with Article III, Section 1, (c), (i) of the 

 International Convention for the High Seas 

 Fisheries of the Xorth Pacific Ocean, for the 

 purpose of ". . . determining need for joint con- 

 servation measures of the Contracting Parties con- 

 ducting substantial exploitation of that stock." 

 (The Contracting Parties in this instance are 

 Japan and the United States.) 



The Bureau of Commercial Fisheries Biological 

 Laboratory in Seattle, Washington (then Pacific 

 Salmon Investigations) was assigned this study 

 for the United States. Investigations began in 

 1954, with emphasis on factors governing yield, 

 e.g., growth recruitment, moitality, and abun- 

 dance. 



In compliance with part of the request, this re- 

 port presents an estimate of growth of adult male 

 king crabs of the eastern Bering Sea and describes 

 methods employed. Although growth of all king 

 crabs is being studied, that of adult males has been 

 given priority, because, the commercial fisheries are 

 concentrated on them and need for their con- 

 servation must, thei'efore, be determined first. 



The authors are indebted to many individuals 

 who contributed toward this study. The Nii^pon 

 Suisan Company, J. E. Shields Company, and 

 Wakefield's Deep Sea Trawlers, Inc. cooperated 

 in recovering tagged crabs; Seiwa Kawasaki, 

 biologist of the Japan Fisheries Agency, recorded 

 very complete tag recovery information, a major 

 contribution; F. C. Cleaver and K. A. Fredin, ad- 

 vised and aided us throughout the study, and T. H. 

 Butler, A. E. Peterson, and W. F. Tliompson pro- 



NOTB. — Fishery BuUetin 200. 

 23, 1961. 



Approved tor pubUcatlon, May 



vided helpful comments concerning the treatment 

 of data. 



BACKGROUND INFORMATION 



The king crab, being a decapod crustacean, has 

 a typical rigid exoskeleton which prevents a 

 change in carapace dimensions except at molting. 

 Consequently the growth of an individual consists 

 of a series of steps, the frequency of which de- 

 creases as the animal increases in age or size. An 

 exception is the mature female king crab, which 

 molts annually prior to egg extrusion, often with- 

 out appreciable increase in carapace dimensions. 



At molting the entire exoskeleton is cast along 

 with the mouth and stomach parts, gills, tendons, 

 and other structures of ectodermal origin. Since 

 all hard parts of the body are lost, detennination 

 of growth must be achieved by means other than 

 those applicable to animal forms which have 

 permanent i-ecords of seasonal growth such as may 

 be found on the scales of fish. 



Several methods have been used to study growth 

 of king crabs. Most of the studies were made by 

 Japanese scientists and depend upon one or com- 

 binations of three basic types of data : Growth in- 

 crement per molt and frequency of molt; size- 

 frequency distributions from 1 year which show 

 modes that are indicative of year classes; and size- 

 frequency distribution data taken in successive 

 years to observe the progression of weak or domi- 

 nant year groups through the years. 



W^ang (1937) described growth rates for young 

 crabs, as interpreted from an examination of 

 modes in size-frequency distribution and for the 

 older crabs by following the progression of modes 

 in size-frequency data collected in 3 successive 

 years. Marukawa (1933) studietl live tank- 

 reared crabs and observed growtli per molt and 

 frequency of molt in conjunction with size- 



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