FISHERY BULLETIN: VOL. 72. NO. 1 



regression line for large old-shell males for 

 relative fullness of brood chamber is quite steep 

 (-0.616) and nearly approaches the slope for 

 large new-shell males (-0.677); however, there 

 are no points in the vicinity of zero to indicate 

 that mating ability for large old-shell males 

 drops off suddenly after a certain number of 

 matings. Furthermore, the other measurement 

 variable indicates that the mating ability of 

 large old-shell crabs does not decline at a signif- 

 icant rate when exposed to a maximum of 18 

 females. 



DISCUSSION 



This study indicates that all classes of males 

 tested i)ossessed considerable ability to mate 

 repeatedly at the approximate rate of one female 

 every 5 days. Mating ability of small old-shell 

 and large new-shell male king crabs decreases 

 markedly after approximately the seventh to 

 ninth mating. The decline for large old-shells 

 and small new-shells is not as noticeable. 



Although the analysis of covariance for this 

 experiment does not indicate significant differ- 

 ences in mating ability attributable to size, one 

 should be hesitant in saying categorically that 

 size is not a relevant factor. By examining the 

 individual slopes in the graphs, it is evident 

 that certain combinations of age and size have 

 a marked effect on mating ability and one must 

 realize that when a given factor is examined, the 

 other factor is averaged out. 



The knowledge obtained as a result of this 

 investigation represents just a beginning in the 

 understanding of the mating of king crabs. To 

 what extent these findings are applicable to 

 mating in nature remain uncertain. The effects 

 of holding experimental crabs in undersea pens 

 must be understood before realizing full appli- 

 cation of the data to practical management of 

 the fishery. 



Holding males in pens could adversely affect 

 mating ability of some classes, particularly later 

 matings after prolonged captivity, while simul- 

 taneously enhancing ability of others by forcing 

 partners into constant close association with 

 one another. Larger females used later in the 

 experiment may also have affected results. 



Even though size does not appear to be a sig- 

 nificant factor in mating ability as far as the 

 number of repeated matings is concerned, and 



even though small males appear to be capable 

 breeders, it remains a possibility that in some 

 instances in nature small males may not serve 

 adequately as brood stock. Measurements of 

 6,804 king crabs captured by divers as mating 

 pairs, 1963-1971, reveal that small young fe- 

 males are the first to mate each season followed 

 three months later by large old females (Powell, 

 Rothschild, and Buss. 1972). Further, males 

 mating in nature with "pubescent" females (i.e., 

 those mating for the first time and therefore the 

 smallest found) are older and larger, averaging 

 42 mm more than females, with grasping ob- 

 served as early as January 9 (Powell, Shafford, 

 and Jones, 1972). 



Apparently male size and male-female ratios 

 are not the only factors affecting mating in 

 nature. The presence in recent years of high in- 

 cidence of adult females without eggs and with 

 partial clutches within certain locations of the 

 Kodiak fishery seem to be fishery-related because 

 they occur only in areas of intense fishing (Pow- 

 ell, 1969'). 



Adult female king crabs form mating congre- 

 gations in shallow water from January through 

 April and these congregations are intermittently 

 distributed throughout the thousands of square 

 miles of shallow habitat. For mating to be suc- 

 cessful in each congregation, adequate numbers 

 of capable males must be present during the 

 relatively brief matable period following female 

 ecdysis, otherwise delayed mating may adverse- 

 ly affect the success of ovulation and subsequent 

 fertilization (Kurata, 1961; McMullen. 1969; 

 and Wallace, Pertuit, and Hvatum, 1958). 



The ratio of males to females necessary for 

 complete mating success in nature appears de- 

 pendent upon factors other than just numbers 

 alone. The rate at which females molt and spa- 

 tial distribution and size differences of adults 

 inhabiting the location are also believed impor- 

 tant. The greater the rate of female molting, the 

 greater the number of males required. Male 

 crabs select partners as early as 16 days prior to 

 mating and continually grasp them until copu- 

 lation occurs soon after female ecdysis (Powell, 

 Rothschild, and Buss, 1972). Because of pre- 

 mating "grasping" behavior, it is possible that 

 females molt without male partners though a 



 Powell Ciuv C. 1969. Some aspects of king crab biol- 

 ogy. Proc. Am.' Fish. Soc. West. Div. Meeting, Jackson 

 Hole, WY, June 1969. (Processed) 



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