Stehlik et al.: Distribution patterns of various crab species in the Hudson-Raritan Estuary 



695 



73° 59' 



74°|15'W 



New York 



74°|00' 



73°] 59' 



74°|15'W 



Figure 1 



Hudson-Raritan Estuary, from New York to New Jersey, with 3-m contour, drawn boundaries, 

 and the nine strata of the Hudson-Raritan Estuary trawl survey. The inset shows the location 

 of the estuary on the United States coast off New York and New Jersey. 



and 1992 temperature and salinity were determined by 

 using a Niskin bottle, a thermometer, and an induction 

 salinometer. Beginning in January 1993 a Hydrolab" 

 Surveyor III multiprobe was used. 



Fish and large invertebrates were counted, weighed, 

 and measured (±1.0 cm), and sexes of the crabs were re- 

 corded. Catch per unit of effort or number per tow was 

 used to estimate relative abundance. Crabs were mea- 

 sured by carapace width (CW) between the tips of the 

 anterolateral teeth. Specimens were saved for dietary 

 analysis from June 1991 through June 1992. These 

 specimens were measured (±1.0 mm) and molt stages 

 were classified as intermolt (hard-shelled), premolt (new 

 skin separates easily from inside the carapace), soft- 

 shelled, or postmolt (early and late papershell). 



For some analyses, we separated crabs into two size 

 classes based on maturity because preferred habitats, 

 tolerances, or reproductive needs may be different for 

 different life stages. Most researchers use a carapace 

 width at which 250% or >80% of the individuals are 

 mature (produce viable eggs or sperm) as a separation 

 boundary. Maturity in males is determined by dissec- 

 tion or by allometric changes in growth of appendages 

 (Hartnoll, 1978; Block and Rebach, 1998; de Lestang 

 et al., 2003). Most female blue crabs in our study area 

 and in Virginia had completed their pubertal molt and 

 thus could reproduce by 12 cm CW (Van Engel, 1958; 



Fisher, 1999; Stehlik, unpubl. data). In Virginia, 80% 

 of male blue crabs are mature by 11.9 cm (Van Engel, 

 1990). In lady crabs from the New York coast, nearly all 

 males are mature at >6 cm, and females at about 5 cm 

 (Briggs and Grahn 3 ). In the middle-Atlantic portion of 

 their range, male rock crabs mature at 5 cm (Haefner, 

 1976) and some females <5 cm bear eggs (Reilly and 

 Saila, 1978). We chose the following CW boundaries 

 for >80% maturity: blue crabs, >12 cm both sexes; lady 

 crabs, 25 cm both sexes; and rock crabs, males ^5 cm 

 and females ^4 cm. 



Data on blue, lady, and rock crabs from NEFSC 

 (Northeast Fisheries Science Center, NOAA) fall bot- 

 tom trawl surveys on the northeast United States con- 

 tinental shelf, 1992-94, were used to expand the geo- 

 graphical viewpoint of our study. The presence of each 

 species in each tow was plotted to show distributions in 

 a representative year. 1992. The plots were made with 

 Surfer® (version 6, Golden Software Inc., Golden, CO). 

 Methods on the trawl surveys are described elsewhere 

 (Azarovitz, 1981). 



3 Briggs, P. T.. and C. M. Grahn. 1996. Aspects of the fish- 

 ery biology of the lady crab tOvalipes ocellatus) in New York 

 waters, 8 p. An in-house paper. New York State Department 

 of Environmental Conservation, 205 North Belle Mead Road, 

 Suite 1, East Setauket, NY, 11733. 



