304 



Fishery Bulletin 89(2), 1991 



1976, Hankin et al. 1985), their overall contribution to 

 the production of planktonic larvae may be relatively 

 equal to or less than that of the less-abundant larger 

 females whose eggs may have a greater chance of sur- 

 viving embryogenesis. 



Cancer anthonyi has a high reproductive potential 

 (Table 4). Estimates of reproductive potential are 

 typically based on the growth, size at maturity, longev- 

 ity, and fecundity of an animal (Campbell and Robin- 

 son 1983). These estimates have been applied to ani- 

 mals having but a single brood per year. Here, we 

 define reproductive potential for an animal capable of 

 producing more than one brood per year (reproductive 

 potential: mean number of eggs produced at mean 

 adult size, minimum and maximum number of mature 

 instars, minimum and maximum number of broods per 

 instar, and the estimated number of broods per year). 

 We use the maximum or entire adult life span because 

 (1) late instar females may contribute most to the 

 overall egg production of their cohort, (2) estimates of 

 adult mortality are unknown for most species, and (3) 

 confounding correlations between fecundity and mor- 

 tality are eliminated (Shields 1991). While admittedly 

 crude, the estimates of reproductive potential are 

 useful for comparisons (Table 4). The reproductive 

 potential of a single female C. anthonyi was estimated 

 at 14.7-29.4 million eggs in her lifetime (2.6 million 

 eggs/brood at mean size, 3-4 broods/year, 2-4 repro- 

 ductive years). Cancer magister has an estimated 

 potential of approximately 3-5 million eggs (1-1.5 

 million eggs/brood, 1 brood/year, 3 reproductive years; 

 MacKay 1942). Neither of these estimates consider 

 smaller broods from older instars or variations in brood 

 size within an instar. 



Most Cancer crabs breed but once a year, making 

 study of their reproduction and reproductive habits 

 logistically difficult. The high fecundity and great re- 

 productive potential of Cancer anthonyi, coupled with 

 its frequent production of eggs, may provide an ex- 

 cellent model for the study of reproduction in Cancer 

 crabs. 



Acknowledgments 



We acknowledge Gil Crabbe for his able fishing and 

 collection of the crabs. We thank Jim Crisp, Teri 

 Matelson, John Jolly, and Teresa Stevens, for their ex- 

 cellent help in collecting and collating the data. JDS 

 and RKO thank Julie Shields and Nicole Barthelemy- 

 Okazaki for moral support. Dr. Glen Jamieson critically 

 improved the manuscript. This work is a result of 

 research sponsored in part by NOAA, National Sea 

 Grant College Program, Department of Commerce, 

 under grant number NA80AA-D-00120, project num- 



ber R/F-75, through the California Sea Grant College 

 Program, and in part by the California State Resources 

 Agency. The U.S. Government is authorized to repro- 

 duce and distribute for governmental purposes. 



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