SIZE AT MATURITY AND FECUNDITY OF ROCK CRABS, 



CANCER IRRORATUS, FROM THE BAY OF FUNDY AND 



SOUTHWESTERN NOVA SCOTIA 



A. Campbell 1 and M. D. Eagles 2 



ABSTRACT 



Rock crabs, Cancer irroratus, were collected from lobster traps, trawls, and by divers in the Bay of Fundy and 

 southwestern Nova Scotia, 1980-81. Estimates of maturity were similar using gonad examination, measure- 

 ments of chela height, and abdominal width/carapace width ratios. The carapace width (C W) at which 50% of 

 male and female rock crabs were mature was estimated to be 62 and 49 mm, whereas the onset of maturity 

 was estimated to be 40 and 2 7 mm CW, respectively. Ovigerous females (range 41-100 mm C W) were heavier 

 than nonovigerous females and males of the same carapace width, and carried from 47,130 to 567,690 eggs 

 per female. Rock crabs in the Bay of Fundy and southwestern Nova Scotia appear to mature at a larger size 

 than rock crabs from more southern waters. 



The rock crab, Cancer irroratus Say, 1817, 

 (Decapoda: Brachyura), is common along the Atlan- 

 tic coast of North America from Labrador to South 

 Carolina (Rathbun 1930; Squires 1966; Nations 

 1975). In Canadian waters, C. irroratus is generally 

 found near the coast (depth < 20 m) and is abundant 

 in the southern Gulf of St. Lawrence (Caddy and 

 Chandler 1976; Stasko 1976; Campbell 1979). At 

 present, C. irroratus is underutilized due to high pro- 

 cessing costs and limited market demand. Conse- 

 quently, rock crabs are fished primarily as an 

 incidental bycatch in the lobster fishery and, except 

 in certain areas, are generally discarded or oc- 

 casionally used as bait in lobster traps. Bigford 

 (1979) summarized the numerous studies on the 

 biology and ecology of C. irroratus. Little information 

 exists on the reproductive biology of C. irroratus in its 

 northern range, especially the Bay of Fundy and 

 southwestern Nova Scotia (Krouse 1972, 1976, 

 1980; Scarratt and Lowe 1972; Elner and Stasko 

 1978; Elner and Elner 1980). 



Size at maturity and fecundity are important 

 parameters in determining reproductive potential 

 and for managing a crab fishery. Crabs can be con- 

 sidered mature when males can mate successfully 

 (Hartnoll 1969) and females are capable of extruding 

 eggs. Although egg-bearing by female crabs is an ob- 

 vious indication of functional maturity, depending on 



1 Invertebrates and Marine Plants Division, Department of 

 Fisheries and Oceans, Biological Station, St. Andrews, N.B. E0G 

 2X0, Canada. 



2 Invertebrates and Marine Plants Division, Department of 

 Fisheries and Oceans, Biological Station, St. Andrews, N.B.; present 

 address: P.O. Box 226, St. Andrews, N.B. E0G 2X0, Canada. 



Manuscript accepted October 1982. 

 FISHERY BULLETIN: VOL. 81, NO. 2, 1983. 



the season and other factors, a proportion of mature 

 females may be found without external eggs at any 

 given period. Estimation of maturity in these non- 

 ovigerous females and males can be determined by 

 internal examination of the gonads (physiological 

 maturity) and/or measurement of external morpho- 

 logical secondary sexual characteristics (functional 

 maturity). This paper reports on the physiological 

 and functional maturity, fecundity, and weight 

 relations of different size-groups of C. irroratus males 

 and females collected from the Bay of Fundy and 

 southwestern Nova Scotia waters (Fig. 1). 



METHODS 



Male and nonovigerous female C. irroratus were 

 collected near Alma, Beaver Harbor, and Grand 

 Manan, New Brunswick, and at Scots Bay, Delap 

 Cove, and Port Maitland, Nova Scotia, by lobster 

 fishermen who used conventional lobster traps dur- 

 ing March-July 1980 (Fig. 1). Additional samples 

 were collected by divers on the southwestern shore of 

 McNutt Island near Shelburne, Nova Scotia, during 

 July 1981. Ovigerous C. irroratus were caught in 

 lobster traps near Alma and on the eastern side of 

 Passamaquoddy Bay, using bottom trawls during 

 January-June 1980 and December 1980-February 

 1981. 



The rock crabs were frozen individually in plastic 

 bags within 6 h of capture and stored at ca — 20°C. 

 Prior to examination, the rock crabs were thawed at 

 room temperature. We recorded the carapace width 

 (CW, widest distance between the tips of the an- 

 terolateral spines of the carapace), the height of the 



357 



