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Fishery Bulletin 98(1) 



but see Toole et al., 1997). However, Able et al. ( 1989) 

 have suggested that there is a lack of studies that 

 examine the continental shelves of the MAB as poten- 

 tial nursery grounds. This is remarkable because 

 the early life history stages of many species of 

 groundfish are believed to inhabit almost the entire 

 shelf as well as the slope (Fahay, 1983; Miller et al., 

 1991). 



A wide assortment of biotic and abiotic variables 

 may have a role in determining the distribution of 

 continental shelf nursery grounds. Variations of abi- 

 otic parameters, such as temperature, salinity, and 

 oxygen, can affect the metabolism of marine flat- 

 fishes during the juvenile stage (Malloy and Tar- 

 gett, 1991: Pihl et al., 1991; Gibson, 1994; Neill et 

 al., 1994). Changes in temperature, for example, can 

 have a marked effect on feeding rate and growth; 

 thus lower temperatures may slow growth and con- 

 sequently increase susceptibility to mortality due to 

 size-selective predation (Van der Veer et al., 1994). 

 Salinity seems to have a small influence on the 

 growth rate of fish, but it is often effective in con- 

 trolling their distribution (Rodgers, 1992). By adjust- 

 ing their position in relation to local abiotic factors, 

 fish may modify their gi'owth rate and survival 

 with respect to average environmental parameters 

 (Gibson, 1994). 



Biotic factors, particularly food resources and shel- 

 ter related to biological activity, may also be a potent 

 determinant of nursery habitat. Auster et al. (1991) 

 found that several biotic microhabitat types, includ- 

 ing amphipod tube mats, shells, and biogenic depres- 

 sions, significantly affected the abundance of fishes 

 and other megafauna. Other biotic factors that influ- 

 ence the distribution of juvenile fishes include the 

 presence of potential predators (Bailey, 1994) and 

 the availability of potential prey species. Biotic fac- 

 tors may be ephemeral; however their presence or 

 absence at a given time and space may control the 

 distribution of associated fish species. The spatial 

 distribution of amphipod tubes in particular have 

 been shown to have a strong influence on the abun- 

 dance of age-0 silver hake {Meiiiicciii^ bilinearis) 

 during fall in the MAB (Auster et al., 1997). 



Recent recruitment research has emphasized fac- 

 tors that affect survival of the early life history stages 

 of fishes. Identification of the habitats preferred by 

 juvenile fishes in offshore waters will allow for a 

 more complete understanding of recruitment varia- 

 tion. Although shelf habitat is magnitudes larger in 

 area than the nearshore habitat traditionally stud- 

 ied, there is currently little knowledge of its role as a 

 nursery. For many flatfish species, the size of nurs- 

 ery habitat and year-class strength have been cor- 

 related (Rijnsdorp et al., 1992; Gibson, 1994). Our 



objectives were to provide a first-order analysis of the 

 species that use the shelf as settlement and nursery 

 habitat during the course of a year and to address 

 the relation of these distributions to environmental 

 correlates. ^ 



Description of the study area 



The New York Bight (NYB), a central portion of the 

 MAB, encompasses an area of 39,000 km^ on the East 

 Coast of the United States. Its boundary extends out 

 to the 200-m isobath between Montauk Point, New 

 York, and Cape May at the southern end of New 

 Jersey. The bathymetry of the NYB varies on sev- 

 eral geographical scales. Although the continental 

 shelf in this area is, to the most extent, gently slop- 

 ing, large-scale features do exist. The Hudson River 

 Canyon, which almost bisects the NYB. is the most 

 obvious of these. Imposed on this bathymetry are 

 the convoluted isobaths of the ridge and the swale 

 topography that dominates the NYB (Freeland and 

 Swift, 1978). Surficial sediments range from fine 

 sand along the southern shore of Long Island to 

 pebbly gi-avel off the coast of New Jersey ( Schlee, 

 1964). On a somewhat smaller scale, the sediments 

 vary in color from yellow ochre to greenish gi'ay and 

 in composition from biogenic calcium carbonate to 

 quartz and feldspar (Freeland and Swift, 1978). 



The hydrography of the NYB changes seasonally. 

 During the winter months, the entire water column 

 is well mixed, but the coldest waters are found near- 

 shore (Bowman and Wunderlich, 1977). Stratifica- 

 tion begins in the spring and peaks in the summer. 

 During stratification, a body of cold dense water, 

 known as the cold pool, remains trapped on the 

 bottom under the pycnocline on the midshelf This 

 cold pool foi'ms a distinct band of midshelf temper- 

 ature minima (about 4-5°C in midsummei) from 

 Georges Bank to Cape Hatteras, persisting from late 

 spring to early autumn (Houghton et al., 1982). Out- 

 side the cold pool, bottom temperatures in the NYB 

 range inshore from less than 1"C in the winter to 

 above 21°C in the summer. Deeper bottom water, 

 near the 100-m isobath, is less variable, ranging 

 from 7° to 12'=C (Ketchum and Corwin, 1964). Salin- 

 ity in the NYB varies less, with only a mild seasonal 

 cycle. The lowest salinities (<31 psu) are found near 

 the apex of the NYB, southeast of the Hudson River. 

 However, salinities as high as 35 psu are found at 

 the 200-m isobath. As with temperature, the largest 

 seasonal fluctuations in salinity are found nearshoi-e 

 ( Bowman and Wunderlich, 1977 ). Overall, nearshore 

 habitats are less stable than those offshore in terms 

 of both salinity and temperature. 



