CAMPBELL and EAGLES: SIZE OF ROCK CRABS 



dominal width/CW ratio (Fig. 4B). There were no 

 ovigerous females in our samples between 48 and 65 

 mm CW; perhaps this scarcity could be attributed to 

 sample bias owing to gear selectivity and/or spatial 

 and temporal effects on the sizes of ovigerous 

 females collected. 



Haefner (1976) showed an increase in development 

 of gonads in relation to CW increase for C. irroratus 

 males and females captured in the mid-Atlantic 

 Bight. In general, the present data suggest that C. 

 irroratus matures at a smaller size in southern than in 

 northern waters of eastern North America. Along the 

 Virginia coastline, the presence of eggs on females, 

 morphological measurements, and observations on 

 gonads of male and female C. irroratus indicated in- 

 dividuals are mature by about 30 mm C W (Shotton 

 1973; Terretta 1973). Reilly (1975) found ovigerous 

 females as small as 14 mm CW, with many ovigerous 

 crabs collected in the 14-25 mm CW range from 

 Rhode Island waters. In northern populations along 

 the Maine coast, Krouse (1972) suggested that 

 females mature at 55-62 mm CW, based on the pres- 

 ence of ovigerous females, although most females 

 were ovigerous in the 70-99 mm CW range. Scarratt 

 and Lowe (1972) examined the gonads of C. irroratus 

 from Northumberland Strait and found the smallest 

 female with mature gonads to be 60 mm CW, but the 

 smallest female with external eggs was 65 mm CW, 

 whereas some males had developing gonads at a 50- 

 100 mm CW range and there were a few with ripe 

 gonads >69 mm CW. The results of this study on C. 

 irroratus in the Bay of Fundy and southwestern Nova 



600 1- 



S.400 



09 

 HI 



200 



log 1Q Y= 0.5827 + 2.5529 log 1Q CW 

 r = 0.8570 

 N = 50 



oi-v 



J_ 



1 



50 60 70 80 



Carapace Width (mm) 



90 



100 



FIGURE 5.— Relationship between total number of eggs (Y) carried 

 externally and carapace width (CW) of ovigerous female rock crabs 

 from the Bay of Fundy and southwestern Nova Scotia; r = correla- 

 tion coefficient, N = number of individuals. 



Scotia generally agree with those of Krouse (1972) 

 and Scarratt and Lowe (1972) in that most ovigerous 

 females were >65 mm CW (Fig. 5). 



The CW-fecundity relationship was described well 

 (r = 0.857) by a power curve (Fig. 5). There were no 

 significant differences (P>0.05) in CW-fecundity 

 relation between newly extruded eggs (orange-red 

 color) and well-developed eggs (pale gray-brown) 

 and between specimens collected in 1980 and 1981, 

 using analysis of covariance; thus the data were com- 

 bined. The smallest ovigerous female (41.1 mm CW) 

 collected had the lowest number (47,130) of eggs. A 

 99.8 mm CW female had the largest number (567, 

 690) of eggs. The only other published estimates of 

 fecundity for C. irroratus are from Rhode Island 

 (Reilly and Saila 1978). There were no significant dif- 

 ferences (.P>0.05) between the fecundity of C. 

 irroratus females in the same size range (37-88 mm 

 CW) from Rhode Island and this study. However, 

 larger ovigerous rock crabs (90-100 mm C W) produc- 

 ing a greater number of eggs (320,000-567,690) per 

 female (Fig. 5) were observed from Bay of Fundy and 

 southwestern Nova Scotia relative to those reported 

 from the Rhode Island area (Reilly 1975; Reilly and 

 Saila 1978). 



Interarea variations between C. irroratus of size at 

 first maturity and fecundity may be caused by a num- 

 ber of factors such as differences in photo-period, 

 temperature, and food availability. Temperatures 

 are generally cooler in northern waters, such as in the 

 Bay of Fundy, compared with southern waters, such 

 as off Rhode Island (Colton and Stoddard 1972). 

 Warmer temperatures probably lead to maturity at a 

 smaller size in C. irroratus compared with colder 

 waters (Kurata 1962). Although C. irroratus from the 

 Bay of Fundy may produce more eggs at larger sizes 

 (90-100 mm CW) than female crabs off Rhode Island, 

 we hypothesized that the reproductive potential of 

 this species is greater in warmer southern waters 

 where more individuals mature at smaller sizes, 

 thereby reducing the population generation time, 

 than those rock crabs in colder northern waters. The 

 integration of growth, size at maturity, and fecundity 

 information to compare the reproductive potential of 

 C. irroratus from these two areas requires further 

 study. 



ACKNOWLEDGMENTS 



We thank S. Bellis, R. Chandler, D. Duggan, D. 

 Graham, S. Hamet, and H. A. Leslie for technical 

 assistance; F. Cunningham for graphics; R. W. Elner 

 and D. J. Scarratt for reviewing earlier versions of 

 this paper. 



361 



