Identification of Continental Shelf Groundfish....
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GRANT NUMBER:  NA66FD0012           NMFS NUMBER:   95-NER-030

REPORT TITLE:  Identification of Continental Shelf Groundfish Nursery Habitats in the New York Bight

AUTHOR:  Robert K. Cowen

PUBLISH DATE: April 21, 1998

AVAILABLE FROM:  National Marine Fisheries Service, Northeast Region, One Blackburn Drive, Gloucester, MA 01930.  TELEPHONE:  (978) 281-9267


While juvenile fish are studied extensively in estuarine and nearshore environments, surprisingly little is known about the basic habitat requirements of juveniles with offshore settlement and nursery areas. Between June 1996 and July 1997, settlement and nursery of 0-group demersal fish on the Continental Shelf of the New York Bight were investigated using a two-meter beam trawl. Replicate tows at 21 stations along three cross-shelf transects (20-95 m depth), were sampled on a near monthly basis to determine the general ecology of these juveniles (21,309 fish collected in 659 tows). Of the 47 species collected, 33 included 0-group juveniles, and 25 near settlement size individuals. the two dominant species, Pleuronectes ferrugineus and Merluccius bilnearis comprised 88.9% of the total catch of 0-group fish, while 94% of all 0-group fish were collected during the summer and fall. Comparisons of weighted means and the use of canonical correspondence analysis determined that settlement and nursery habitats across the shelf are delineated primarily by depth, temperature, and time of year. Three zones across the shelf (inner, middle and outer shelf) each had distinct juvenile fish assemblages, although cross-shelf movements between settlement and nursery areas were apparent for some species. Knowledge gained about the distribution and quality of juvenile habitats for commercially important offshore species should facilitate their improved management. Silver hake juveniles were collected during 10 cruises, beginning in June 1996, but primarily in September and October 1996, on the outer Continental Shelf in depths from 60-95 meters. The means size of the silver hake was inversely proportional to temperature. Otolith analysis of silver hake were used to calculate the mean age and length at settlement (34.5 days & 15 mm), as well as pre-and post-settlement growth rates along a temperature gradient (8-12 degrees C) indicate that silver hake in areas of cooler bottom temperatures (~9 degrees C) were not only larger and higher in abundance, but were also faster growing. This pattern suggests that within the range of the settlement area exhibited by silver hake, the quality of habitat (in terms of realized growth) may be enhanced on the outer Continental Shelf where these cooler waters occurred in the fall.

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