GROWTH OF THE ADULT MALE KING CRAB 



57 



defined for the very-old-sliell conditioii, l)Ut is be- 

 lieved to be notic-euble in tiie second yeiir sifter 

 liist molt. Individual foulin<r or<ranisms which 

 settle on the shell have not been considered as a 

 '-ip.nsui-e of time since moltin<r because the life 

 cycle, such as time of settin^^ ;iiid jrrowth of these 

 orjianisms in the Bering: Sea is not known and 

 would demand a separate study. 



Shell conditions are tlie basis of determining^ 

 molting: frequency, and for the purpose of growth 

 we are interested in those that molted in the cur- 

 rent year and those that did not. In tlie remain- 

 der of this report soft and new-shell conditions 

 are irronj)ed as new-shell and refer to crabs that 

 have molted in the current year, while old- and 

 very-old-shell conditions are grouped as old-shell 

 and refer to crabs which have not molted during 

 the current year. 



Since initiation of investigations in 1954, crabs 

 have been tagged with either a Petersen disc-type 

 tag on a leg or through the carapace, or with a 

 spaghetti-type tag through the muscular isthmus 

 between the posterior margin of the carapace and 

 the abdonimal region. Since Petersen disc-type 

 tags are probably lost at molting, analysis of 

 growth from tagged crab data has been restricted 

 to recoveries of spaghetti-type tags which remain 

 attached through molt. 



Of 23,826 male crabs released with spaghetti- 

 type tags in years 1955 through 1959, 1,108 have 

 been recovered, of which 1,017 were returned with 

 complete measurement data. Changes in sizes in- 

 dicating growth wei'e observed in .325 recoveries. 



ADEQUACY OF DATA 



Two population properties are assumed in this 

 report. They are: (1) the growth of tagged in- 

 dividuals and the size frequency distribution sam- 

 ples are representative of the population, and (2) 

 the same population is sampled each year. Sup- 

 port for these assumptions is provided from e.\ani- 

 ination of our field observations which show : 

 tagged crabs mix uniforndy with the untagged 

 crabs throughout the fishing area; rejietitive sam- 

 pling performed in 1956 and again in 1958 re- 

 sulted in similar size-fre(|uency distributions and 

 percentages of shell conditions within eacli year; 

 tagged crabs continue to be taken in successive 

 years after release, and only in the Bering Sea. 

 In addition, the sampling areas, particularly since 



1957, are believed to include the major distribu- 

 tion of this population, since explorations by the 

 United States Fish and AVildlife Service in 1949 

 (Ellson, Powell, and Hildebrand, 1950) and by the 

 JapanevSe in 1957 (Fisheries Agency of Japan, 

 1958) revealed very few PniaJitliodescamtsciuiticu 

 in adjacent areas of the eastern Bering Sea. 



In subsequent discussions, it will be evident that 

 the 1957 data are anomolous witli other years. 

 The samples included fewer molters in the popu- 

 lation, thus reducing the proportion of molting to 

 nonmolting crabs. K.xamination of this feature 

 shows that the 1957 data were collected later in 

 the sununer than in any of the other years. It is 

 therefore possible that changes in distribution as- 

 sociated with this time period may atfect the avail- 

 ability of new-shell crabs. That only new-shell 

 crabs are atfected is suspected by examination of 

 all data which shows that the abundance of old- 

 shell crabs appear relati\ely unclianged regardless 

 of the time of sampling. 



There is general agreement in published reports 

 that male crabs larger than 110 mm. in carapace 

 length, molt no more than once annually. From 

 a study of shell conditions, Vinogradov (1945) 

 established that the majority of the larger males 

 molt once e\ery 2 years. Also our records show 

 that several tagged crabs were returned after 3 

 years with no evidence of molting. 



The Fishery Market News (1942), Wallace, 

 Pertuit, and Hvatum (1949) and discussions with 

 fishermen indicate that the adult male king crab 

 molting period and growth occur in late winter 

 or early spring in the eastern Bering Sea. Our 

 observations aboard chartered vessels show that 

 soft-shell male crabs were caught only in May, 

 and these have numbered one-tenth of 1 percent 

 of the total number of males sampled. No male 

 crabs in the molting or postmolting stages have 

 been found in the summer and late fall surveys. 

 Since growth takes place before our sampling 

 periods, and there is no noticeable change in size- 

 frequency distribution or shell-condition propor- 

 tions during the sampling season, the crabs taken 

 may be considered as representing an instanta- 

 neous sample. 



The relation between time of molting and our 

 period of sampling is an important part in difl'er- 

 entiating, through the use of shell condition, the 



