Small collections of rock crabs were made in Maine (Portland and 

 Boothbay Harbor) where shell blackening was not recorded but 15% 

 (30/206) had perforating shell lesions (4 with perforation of the 

 appendages and 26 with perforations of the carapace) . Other 

 collections near Ocean City, Maryland, and in proximity to the 

 closed Philadelphia-Camden sewage sludge disposal site showed that 

 39% (39/99) of the large crabs caught in traps 16 miles offshore 

 had shell disease. In contrast, none of 103 recently molted 

 specimens caught inshore during January through March had evidence 

 of shell disease. 



In conclusion, studies on the rock crab, C. irroratus , are 

 more extensive than on other decapod species examined in the New 

 York Bight. Background information has shown that migratory 

 behavior and molting by some crustaceans may vary seasonally 

 between inshore, near shore, and offshore populations. 

 Male: female ratios approaching 1:1 are indicative of seasonal 

 mating activity by C. irroratus . The peak prevalence of shell 

 disease occurs during intermolt periods since blackening and non- 

 perforating lesions may be cast off with the old shell. Limited 

 data indicate that the more northern population may serve as an 

 indicator of perforating shell disease associated with 

 chitinoclastic bacteria, while mid-Atlantic coastal and shelf 

 populations may also be affected by shell blackening as well as 

 perforating lesions due to bacteria and/or other unknown causes. 



Perforations and/or shell blackening have been seen in Jonah 

 crabs, but the number of specimens studied has been too small to 

 support estimates of disease prevalence in this species. 

 Furthermore, molting data for C. borealis are insufficient to 

 define seasonal patterns (Haeffner, 1977) . 



2 . 4 Shell Disease in Blue Crabs 



Information on causes of shell disease and damage in blue 

 crabs from the Pamlico River, North Carolina has been provided by 

 S. McKenna and co-workers (unpublished report). Portions of the 

 river have experienced numerous fish kills, algal blooms, anoxic 

 events, and outbreaks of fish disease associated with poor water 

 quality. Trawl catches of 1,459 crabs showed that 5% had severe 

 lesions on the dorsal surface of the carapace, and pot catches 

 had prevalences as high as 10%. Bacteriological studies on the 

 lesions yielded species of Pseudomonas . Vibrio , and Proteus . 



D. Engel and co-workers (unpublished data) have stated that 

 chitinoclastic disease normally associated with blue crabs 

 produces lesions on the ventral surface of the animals, and is 

 usually a coalescence of individual small lesions. However, the 

 disease observed in the Pamlico River affects the dorsal surface 

 of the crabs and appears to be an extremely aggressive form of 

 chitinoclastic disease. Vibrio and Pseudomonas , as well as other 

 bacteria and fungi, have been isolated from the lesions. It is 

 not known why the disease in Pamlico River crabs affects 

 different portions of the exoskeleton, or whether more than one 



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