most females with eggs are found in the Gulf 

 proper (Daugherty, 1952). 



Aside from size variation associated with the 

 annual growth cycle, there is an apparent varia- 

 tion in size correlated with location in which the 

 animals are found (Van Engel, 1958). Though 

 never conclusively proved by experiments, it is 

 thought that there is a negative correlation of size 

 with the salinity in which a crab matures. Very 

 large males are probably large because they have 

 remained in water of low salinity. Fischler (1959) 

 reviewed the occurrence of "dwarf" ovigerous 

 females ranging in width from 52.3 to 80 mm. 

 All these specimens were taken near the sea, and, 

 as the author pointed out, may be small because 

 of environmental influences of high salinities 

 throughout life. 



That the blue crab can tolerate fresh water is 

 well established. The subject is reviewed in some 

 detail by Odum (1953). On the basis of experi- 

 ment and observation he reached the conclusion 

 that oligohaline (100-1,000 p.p.m. CI) and nearly 

 oligohaline waters (25-100 p.p.m. CI) can be in- 

 vaded to a considerable extent if the crabs are 

 able to adjust slowly to the reduced chlorinity, 

 which, of course, is the case in natural invasions. 

 Many of the Florida streams and lakes are oligo- 

 haline and contain blue crabs, but in other areas 

 this is not true and blue crabs in such areas are 

 seldom found far from salt water. 



Because the blue crab supports the largest crab 

 fishery in the United States, fluctuations in abun- 

 dance (especially in the Chesapeake area) have 

 been the subject of many conjectures and a num- 

 ber of investigations. Pearson (1948) dealt with 

 this subject at length. The fluctuations appear to 

 be associated with variable rates of survival in 

 the first year of life. No correlation was found 

 between relative abundance of female crabs and 

 their progeny. On the basis of examination of 13 

 generations, size of spawning stock did not deter- 

 mine size of population surviving to commercial 

 age at the rate of fishing prevailing during the 

 years studied. Pearson found evidence that exces- 

 sively cold weather may reduce availability of im- 

 mature and adult crabs either by direct mortality 

 or by making crabs less available to the fishery 

 immediately after the periods of cold weather. 

 Heavy runoff in some wet years may lower salin- 

 ity in the spawning areas enough to have an ad- 



verse effect on survival of young, but such limits 

 are poorly understood. 



Piers (1923) reported a population of blue 

 crabs in Nova Scotia, the recorded northern limit 

 for the species, and considered that it was a 

 natural rather than an introduced population. 

 Bousfield (personal communication) reports that 

 the species is certainly no longer endemic there. 

 Scattergood (1960) commented that fluctuations 

 in the population in Maine seemingly were corre- 

 lated with temperature when a series of warm 

 years accompanied an increase in number of blue 

 crabs. 



The blue crab is often summarily dismissed as 

 a scavenger. Though it may be a scavenger, and, 

 indeed, is lured to crab pots or wire traps by 

 means of dead fish used for bait, students of the 

 feeding habits of the species agree that it is an 

 omnivore and prefers fresh to putrid flesh 

 (Churchill, 1919; Truitt, 1939; Van Engel, 1958). 

 Darnell (1961) showed that blue crabs in Lake 

 Pontchartrain, La., eat a variety of materials in- 

 cluding fishes, large and small bottom animals, 

 some vascular plant material, and organic detri- 

 tus. Of these materials, the category including 

 small bottom animals (e.g., those that are inti- 

 mately associated with the bottom) made up 

 about half of the diet. There are numerous notes 

 on feeding and predation in the literature record- 

 ing such habits as feeding on oysters, clams, and 

 tunicates. 



In a study of gill area correlated with degree of 

 activity and habit of several species of crabs, Gray 

 (1957) found that the blue crab has a larger gill 

 area per gram of body weight than the other por- 

 tunids studied ( Ovalipes, Arenaeus, and Portunus 

 spp.) and, in fact, exceeded that of any crab 

 studied among aquatic, intertidal, and land crabs 

 in the Beaufort, N.C., area. The blue crab is 

 noted for its vigorous and pugnacious nature, and 

 this anatomical feature gives one reason for such 

 temperament. 



Callineetes sapidus is fairly long-lived follow- 

 ing its last molt, and thus affords a lodging place 

 for barnacles and bryozoans. Its gills and gill 

 chambers become clogged with clusters of a small 

 stalked barnacle, Octolasmus lowei (Causey, 

 1961). The barnacles Balanus amphitrite and 

 Chelonibia patula attach to the carapace. The 

 sacculinid parasite, Loxothylacus texanus, lives 



MARINE DECAPOD CRUSTACEANS OF THE CAROLINAS 



171 



