Shields et al.' Fecundity and reproductive potential of Cancer anthonyt 



303 



(Shields, Okazaki, and Kuris, pers. ob- 

 serv.), and C. productus (Knudsen 1964). 



Ovigerous Cancer anthonyi occur 

 throughout the year in southern Califor- 

 nia. The proportion of ovigerous females 

 in the female crab population varied 

 seasonally, with a peak in the number of 

 ovigerous crabs in March and a nadir in 

 the ovigerous population in June (Reilly 

 1987). Crab fecundity, however, followed 

 an opposite pattern. Cancer antennarius, 

 which has a geographic range similar to 

 C. anthonyi, bears eggs throughout the 

 year with a peak in reproduction during 

 the winter months (Carroll 1982). 



Ovigerous C. anthonyi were highly 

 fecund. Although body size and fecundity 

 are highly correlated in the Brachyura 

 (Hines 1982), for Cancer the larger crabs 

 C. magister and C. pagurus bear relative- 

 ly fewer eggs than C. anthonyi (Table 4). 

 Differences in fecundity may be partial- 

 ly explained by differences in egg and 

 zoea I size, and the duration of embryo- 

 genesis (Table 3), which in turn may be 

 explained by climatic regime (Hines 

 1986). While the data remain incomplete, 

 we note two general patterns: (1) Some 

 species of Cancer produce many small eggs (higher 

 fecundity) that quickly develop into small larvae, and 

 (2) some species produce relatively larger eggs (lower 

 fecundity) that slowly develop into large larvae. 



Decreases in fecundity per pleopod during embryo- 

 genesis are mostly a result of nemertean predation or 

 mechanical abrasion (Shields et al. 1990). The decrease 



Table 3 



Comparative features of embryogenesis (diapause, D), egg size (widest diam- 

 eter), length of zoea I, duration of larval development (zoea I to megalopae), 

 female size at maturity, and fecundity for ten species of Cancer. Unknown 

 data are indicated (?). 



* Length of zoea I is carapace vertex to telson tips. Data from Ingle (1981). 

 ** Does not include duration of megalopa stage. 



References: 'Carroll 1982, Shields et al. unpubl. data; 2 This study, Ander- 

 son and Ford 1976; 3 Haefner 1977, Carpenter 1978; 4J9 Knudsen 1964; 

 4.6.7,9 Orensanz and Gallucci 1988; 5 Shotton, 1973, Krouse 1976, Haefner 1976, 

 Reilly and Saila 1978, Campbell and Eagle 1983; 6 Wild 1983abc, Hankin et 

 al. 1985, Shirley et al. 1988; 8 Edwards 1979, Brown and Bennett 1980, 

 Nichols et al. 1982, Le Foil 1986; 9 Toole 1985; '"Gutierrez and Zuniga 1976. 



is apparently related to crab size; larger crabs appear 

 to lose relatively fewer eggs throughout embryogenesis 

 than do smaller crabs. The impact of nemertean pred- 

 ators on the fecundity of the shore crab Hemigrapsus 

 oregonensis, was also greater on smaller crabs (Shields 

 and Kuris 1988b). While smaller crabs may be more 

 numerous in a population (e.g., Gutierrez and Zuniga 



