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
ABSTRACT

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.