DISTRIBUTION AND CATCH COMPOSITION OF JONAH CRAB, 



CANCER BOREALIS. AND ROCK CRAB, CANCER IRRORATUS, 



NEAR BOOTHBAY HARBOR, MAINE' 



Jay S. Krouse^ 



ABSTRACT 



An analysis of research and commercial catch data of Jonah crab. Cancer borealis. and rock crab, C. 

 irroratus. collected near Boothbay Harbor. Maine, revealed dissimilarities in the distribution of the 

 two species. Jonah crabs were more numerous at the deeper, seaward sampling sites with rocky 

 substrates, while rock crabs were more abundant on soft mud bottoms of the shallower estuarine 

 stations. Distribution of both species is dependent upon the environmental factors of temperature, 

 depth, and substrate type. Absence of Jonah crabs <67 mm carapace width in all collections, indi- 

 cates that, unlike the rock crab, the nursery areas of the Jonah crab are not in nearshore waters. Sex 

 ratios varied seasonally and spatially for rock crabs and seasonally for Jonah crabs. These variations 

 seem to be related to changes in local abundance as the result of movement in association with the 

 reproductive and molting cycles. 



Jonah crab, Cancer borealis, and rock crab, C. ir- 

 roratus, make up a small but increasingly impor- 

 tant commercial fishery along the Maine coast. 

 Since 1966, the price per pound of crabs paid to the 

 fisherman has increased from 40 to 12c (Figure 1 ). 

 As a result the Maine lobstermen have been sell- 

 ing their incidental catches of crabs to offset in- 

 creasing operational costs (bait, fuel, etc.). In view 

 of the current retail price of American lobster, 

 Homarus americanus, which often exceeds $3.00/ 

 lb, the value of the very palatable crab may be 

 expected to continue to increase. In fact, some 

 dealers are now paying 20C to 25c/lb for crab. 



Despite the present economic value (reported 

 1977 landed value was $142,106) of Maine's crab 

 fishery and its potential for future growth, there is 

 little information on the biology of either of the 

 cancrid crabs. While several investigators have 

 studied various aspects of the life history of C. 

 irroratus, very little work has been done on C. 

 borealis other than by Haefner (1977) and Car- 

 penter ( 1978) on the distribution and biology of C. 

 borealis on the continental shelf of the Mid- 

 Atlantic Bight and by Sastry (1977) on the larval 

 development of C. borealis. 



To supplement these studies, I have: 1) 



'This study was conducted in cooperation with the U.S. De- 

 partment of Commerce, National Marine Fisheries Service, 

 under Public Law 88-309, as amended. Commercial Fisheries 

 Research and Development Act, Project 5314. 



^Maine Department of Marine Resources, West Boothbay 

 Harbor, ME 04575. 



examined the size and sex composition and dis- 

 tribution of Jonah crabs in commercial and re- 

 search catches in Maine waters; 2) described the 

 width-weight relationship of the Jonah crab; and 

 3) compared the distribution, size, and sex compo- 

 sition of Jonah and rock crabs from commercial 

 and research catches. 



METHODS 



Jonah crabs were caught incidental to the lob- 

 ster sampling program of the Maine Department 

 of Marine Resources during which vinyl-coated 

 wire (2.54 x 2.54 cm mesh) and conventional 

 wooden lobster traps were fished at nine locations 

 (Figure 2) near Boothbay Harbor, Maine, from 

 July 1968 to December 1974. 



At the time of capture, each crab was sexed and 

 measured. Carapace width (CW), distance be- 

 tween the two outermost notches on the anterolat- 

 eral border of the carapace, was recorded to the 

 nearest millimeter. 



Width-weight relations were calculated for 110 

 male (89-160 mm CW) and 90 female (96-131 mm) 

 Jonah crabs caught by commercial fishermen near 

 Boothbay Harbor. 1973 through 1976. Wet 

 weights were recorded to the nearest 10 g. Linear 

 regression of weight on carapace width was fitted 

 by the method of least squares to logarithmically 

 (base 10) transformed data, and analysis of 

 covariance was used to evaluate the regression 

 coefficients of males and females for differences. 



iManuscript accepted April 1979 

 FISHERY BULLETIN; VOL. 77, NO 3, 



685 — 



