302 



Fishery Bulletin 89(2). 1991 



5.6 5.7 



Fecundity per pleopod (log) 



Figure 3 



Relationship between fecundity per pleopod (X) and 

 fecundity per crab (Y) for 12 crabs (log Y = 2.124 + 0.765 

 log X, R = 0.782, JV = 12, P<0.01). The regression equa- 

 tion was used to calculate fecundity per crab for estimates 

 of reproductive potential for Cancer anthonyi. 



MAM 

 N = 9 48 41 30 25 20 47 23 43 49 



Month 



Figure 4 



Seasonal variation in the fecundity per pleopod of 

 Cancer anthonyi. Months with significantly less fecun- 

 dity than other months are denoted with an asterisk 

 (ANOVA, Sidak's inequality, P<0.05). Bars represent 

 standard error of the mean; N = sample size; dashed 

 line = mean fecundity. 



correlated with crab size (R 0.449, P>0.05, N 12). 

 The partial correlation of fecundity with crab size was 

 significant when fecundity per pleopod was held con- 

 stant (partial correlation: R 0.635, P<0.05, N 12). 

 Thus, projections of reproductive potential (based on 

 estimates of the fecundity per crab) were derived from 

 the correlation of fecundity per pleopod with fecundity 

 (Fig. 3). 



In addition, the relationship between fecundity per 

 pleopod and crab size was significantly influenced by 

 embryogenesis (Fig. 2). Slopes of the regressions and 

 adjusted mean fecundities were significantly different 

 between EDS groups (ANCOVA, adjusted means, 

 F (2 , 315) =224.57, P<0.01; separate slopes, F = 62.71, 

 P<0.01). Fecundity was not correlated with crab size 

 when hatching was imminent (Fig. 2). 



Seasonal relationships 



Crab fecundity varied seasonally (Fig. 4). Fecundity 

 data from both years were combined for the seasonal 

 analysis since their seasonal patterns were similar 

 (ANOVA, log transformation, between years, within 

 months, P>0.05). In February, March, and August, the 

 mean fecundity/pleopod was lower than at other times 

 of the year (ANOVA, log transformation, Sidak's in- 

 equality by month, P<0.01). The differences in mean 

 fecundity/pleopod cannot be attributed to differences 

 in crab size (CW) or developmental stage (EDS) dur- 



ing those months (two-way ANOVA with interaction, 

 P>0.05, n.s.); they represent seasonal fluctuation in 

 crab fecundity. 



The size-fecundity relationship was significantly af- 

 fected by seasonality. Crabs in late-winter and late- 

 summer months (February, March, and August) brood- 

 ed significantly fewer eggs than crabs of similar size 

 in other months (ANCOVA, adjusted means of log 

 fecundity/pleopod = 5.522 ± 0.012 (SE) versus 5.564 

 ±0.006, respectively, P<0.0025). The slopes of the 

 regression of log size on log fecundity/pleopod were 

 also different between seasons (ANCOVA, separate 



Slopes analysis, bvrinter.summer = 1.556 versus bspring.faii 



= 2.573, P<0.001). While these data show significant 

 statistical variations, their biological significance re- 

 mains speculative. 



Discussion 



Most Cancer crabs carry a single brood through a single 

 reproductive season. While multiple ovipositions after 

 a single mating have been reported, they generally oc- 

 cur in two or more reproductive seasons (Williamson 

 1904, Knudsen 1964, Krouse 1972, Haefner 1976, 

 Ebert et al. 1983). Indeed, multiple ovipositions dur- 

 ing a single reproductive season have only been 

 reported for C. anthonyi (this study), C. antennarius 



