693 



Abstract— Blue tCallinectes sapidus) 

 (Portunidae), lady (Ovalipes ocella- 

 tus) (Portunidae I, and Atlantic rock 

 (Cancer irroratus) (Cancridae) crabs 

 inhabit estuaries on the northeast 

 United States coast for parts or all 

 of their life cycles. Their distribu- 

 tions overlap or cross during cer- 

 tain seasons. During a 1991-94 

 monthly otter trawl survey in the 

 Hudson-Raritan Estuary between 

 New York and New Jersey, blue and 

 lady crabs were collected in warmer 

 months and Atlantic rock crabs in 

 colder months. Sex ratios, male: 

 female, of mature crabs were 1:2.0 

 for blue crabs, 1:3.1 for lady crabs, 

 and 21.4:1 for Atlantic rock crabs. 

 Crabs, 1286 in total, were sub- 

 sampled for dietary analysis, and 

 the dominant prey taxa for all crabs, 

 by volume of foregut contents, were 

 mollusks and crustaceans. The pro- 

 portion of amphipods and shrimp in 

 diets decreased as crab size increased. 

 Trophic niche breadth was widest for 

 blue crabs, narrower for lady crabs, 

 and narrowest for Atlantic rock crabs. 

 Trophic overlap was lowest between 

 lady crabs and Atlantic rock crabs, 

 mainly because of frequent consump- 

 tion of the dwarf surfclam (Mulinia 

 lateralis) by the former and the blue 

 mussel (Mytilus edulis) by the latter. 

 The result of cluster analysis showed 

 that size class and location of capture 

 of predators in the estuary were more 

 influential on diet than the species 

 or sex of the predators. 



The Hudson-Raritan Estuary as a crossroads 

 for distribution of blue (Callinectes sapidus), 

 lady (Ovalipes ocellatus), 

 and Atlantic rock {Cancer irroratus) crabs 



Linda L. Stehlik 

 Robert A. Pikanowski 

 Donald G. McMillan 



James J, Howard Marine Sciences Laboratory 



Northeast Fisheries Science Center 



National Marine Fisheries Service, NOAA 



74 Magruder Road 



Highlands, New Jersey 07732 



E-mail address (for L L Stehlik): Linda Stehlika' noaa.gov 



Manuscript submitted 27 November 

 2000 to the Scientific Editor's Office. 



Manuscript approved for publication 

 4 May 2004 by the Scientific Editor. 



Fish. Bull. 102:693-710 (20041. 



The blue crab (Callinectes sapidus) 

 (Portunidae), the lady crab {Ovali- 

 pes ocellatus) (Portunidae), and the 

 Atlantic rock crab (Cancer irroratus) 

 (Cancridae) are the largest and most 

 common brachyuran crabs inhabiting 

 both estuaries and inner continen- 

 tal shelves of the northeast coast of 

 North America. The centers of abun- 

 dance of these three species over- 

 lap in estuarine and coastal waters 

 from New York to Virginia, although 

 their ranges along the northwest 

 Atlantic coast are broad. The blue 

 crab is nearly always an estuarine 

 resident, except during its larval 

 stages, and ranges from the waters 

 off Nova Scotia to Argentina (Wil- 

 liams, 1984). The northernmost estu- 

 aries where the species is abundant 

 enough for commercial harvest are 

 in New Jersey and New York (Briggs, 

 1998; Stehlik et al., 1998). The lady 

 crab is distributed from the waters 

 off Prince Edward Island to those 

 off Georgia but it is most numerous 

 from Georges Bank to Cape Hatteras 

 (Williams, 1984). The Atlantic rock 

 crab (referred to as "rock crab" in 

 this article) is distributed in waters 

 from off Labrador to Florida but is 

 most common in estuaries from Nova 

 Scotia to Virginia (Williams, 1984; 

 Stehlik et al., 1991). Seasonal migra- 

 tions are common for all three spe- 

 cies. Although Jonah crabs (Cancer 

 borealis) are present on the continen- 



tal shelf, they are not included in the 

 present study because they are rare 

 within the Hudson-Raritan Estuary 

 where our study was conducted. 



Physiological tolerances and habi- 

 tat preferences of these crabs have 

 been extensively studied. In eastern 

 United States estuaries the blue crab 

 occurs in shallow to deep, sandy to 

 muddy estuaries and tributaries 

 along marsh edges, and in seagrass 

 (Van Engel, 1958; Milliken and Wil- 

 liams, 1984; Hines et al., 1987; Wil- 

 son et al., 1990; van Montfrans et 

 al., 1991; Rountree and Able, 1992). 

 In the colder portions of its range, 

 it becomes less active at about 15°C 

 (Leffler, 1972), and buries itself, with- 

 out eating, when the temperature is 

 <5°C (Auster and DeGoursey, 1994). 

 It survives at 34°C (Leffler, 1972) and 

 at salinities from to 50 ppt (Guerin 

 and Stickle, 1992). The lady crab is 

 most common on sand substrates 

 (Williams, 1984). It is present on the 

 inner continental shelf from off Cape 

 Cod to off the Carolinas throughout 

 the year (Stehlik et al., 1991). Its tem- 

 perature tolerance is unknown, but it 

 does not survive in <21 ppt (Birchard 

 et al., 1982). The rock crab's optimum 

 temperature range for activity is 14- 

 22°C (Jeffries, 1966); thus the species 

 avoids high summer temperatures. 

 It is found on many substrates, such 

 as sand, mud, bare rock, cobble, and 

 algal beds. 



