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| Current fisheries research and future ecosystems science in the Northeast Center: collected
abstracts of the Northeast Fisheries Science Center’s Eighth Science Symposium, Atlantic City, New Jersey,
February 3-5, 2004. Northeast Fish. Sci. Cent. Ref. Doc. 04-01
SESSION IV |
| Modeling study of movement and settlement
of the Atlantic sea scallops in the Northeast United States Coastal Region |
Session IV, Abstract IV-1
ORAL PRESENTATION |
Zhizhang Yang, David G. Mountain, Devorah
Hart, and Paul Rago
NOAA/NMFS/NEFSC, 166 Water Street, Woods Hole, MA 02543-1026 |
The
movement and settlement of scallops during the life stages from the
fertilized egg until larval settlement
are modeled using a prognostic, individual-based particle tracking
model (IBM). In the model, the scallop larvae are represented by particles
of various biological characteristics, which include the number of
larvae each particle represents, the age and temperature dependent
growth rate, life-stage dependent swimming behaviors, diel migrations,
and random walks. The particles are allowed to migrate in a 3-dimensional
monthly mean climatological flow field while retaining the larval biological
behaviors. The flow field is resolved using a prognostic, finite volume,
hydrodynamic model. The larval movement at each model time step is
determined by the combined velocity of both the physical flow field
and the larval swimming rate.
Three aspects of interests
are researched: (1) The larval retention
over Georges Bank and biological connectivity between the Georges Bank
and the Mid-Atlantic Bight are investigated, (2) The biomass abundance
in four shellfish closed areas, namely Closed Area I, Closed Area II,
Nantucket Lightship Closed Area, and Hudson Canyon Closed Area, are
examined. The origins of the settled larvae and the settlement of
the larvae initiated from the areas are tracked. Statistics of the
larval depth, size and age are estimated, (3) The modeled scallop abundance
based on the years 1993 and 2001 egg production rates are compared
with the years 1995 and 2003 recruitments, respectively. Daily mortality
rates are estimated based on the comparison. In addition, the implications
of the water temperature fluctuations and the random factors inherent
in the physical flow fields and larval biological behaviors to the
model results are examined. The potential applications to fishery
management are addressed.
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| The influence of surface layer salinity changes
on wintertime convection in Wilkinson Basin, Gulf of Maine |
Session IV, Abstract IV-2
ORAL PRESENTATION |
Maureen H. Taylor and David G. Mountain
NOAA/NMFS/NEFSC, 166 Water Street, Woods Hole, MA 02543-1026 |
Observations
suggest that interannual variation of wintertime convection in Wilkinson
Basin is determined to a large
extent by variation in the surface layer salinity in the western Gulf
of Maine (wGOM). This hypothesis is tested using the Price, Weller,
Pinkel (PWP) 1-dimensional mixed layer model to simulate the water column
structure over the cooling period (October through March). Comparisons
are made between the convection potential for cases representing the
range of observed surface layer salinity values. Model results indicate
that the depth of convection can increase by as much as 50% when the
salinities in the wGOM are high. In addition, density distributions
in the wGOM in high salinity years suggest that winter-cooled water from
the adjacent shallow coastal areas can become sufficiently dense to cascade
into the deeper layers of Wilkinson Basin and enhance the convective
cooling. The interannual variation in wintertime convection and in the
resulting density structure has important implications for the onset
of the spring production cycle. The associated variation in deeper layer
temperatures has additional implications for the living marine resources
in the region.
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| Benthic
macrofauna and sedimentary habitats of
the closed areas on Georges Bank |
Session IV, Abstract IV-3
ORAL PRESENTATION |
Joseph J. Vitaliano1, Robert
N. Reid1, and Page Valentine2
1NOAA/NMFS/NEFSC, 74 Magruder Rd., Highlands,
NJ 07732
2USGS, Woods Hole Field Office, 384 Woods Hole
Rd., Woods Hole, MA 02543 |
The
Benthic Habitat/Gear Effects Study began in June 1999 to monitor
the recovery of the benthic habitats
in the closed areas on Georges Bank. Bottom grab samples for enumeration
of benthic macrofauna and for determination of sediment grain size
and sediment TOC content were taken during each cruise. Benthic invertebrates
are important to the Georges Bank ecosystem since they are a major
food source for demersal resource species. Still photos and video
of the sedimentary habitats were also taken and many of these correspond
to the locations where benthic grabs were taken. A brief survey of
the sedimentary habitats found in the closed areas and the benthic
invertebrates that live on or in these sediments will be presented
in this talk. The information gathered during these cruises can be
used not only to monitor recovery of the closed areas but also to create
habitat maps of Georges Bank. The habitat maps will help guide future
research and fisheries/ecosystem management.
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| Yellowtail flounder cooperative tagging study |
Session IV, Abstract IV-4
ORAL PRESENTATION |
Azure D. Westwood and Steve X. Cadrin
NOAA/NMFS/NEFSC, 166 Water Street, Woods Hole, MA 02543-1026 |
The
Northeast Fisheries Science Center is working alongside commercial
fishermen in a region-wide yellowtail
flounder cooperative tagging project. The study was designed, performed
and revised in collaboration with New England groundfishermen; MA and
RI state fisheries, fishing and conservation organizations and Canada’s
Department of Fisheries and Oceans. The project aims to tag yellowtail
aboard commercial fishing vessels with conventional Petersen disc tags
and data-storage tags from Maine to the Mid Atlantic with the objectives
of estimating movement among stocks areas, mortality within stock areas
as well as providing growth observations. The project also aims to
demonstrate successful cooperation between the NEFSC and industry for
future projects and working relations.
This project coordinates
several concurrent field studies with a common tagging protocol,
a single experimental and analytical design,
the same tag return system as well as coordinated outreach efforts. Through
the cooperation of industry leaders and fishery scientists, the study
was planned to reduce uncertainty in yellowtail flounder stock assessments,
thereby improving fishery management. Further details on the project
design and results are available online at: www.cooperative-tagging.org.
In 2003, during cooperative
field work by NEFSC, Rhode Island Fish & Wildlife
and the School for Marine Science and Technology, 9334 yellowtail were
tagged from the Gulf of Maine to the Mid Atlantic, 186 of which were
tagged with data-storage tags. Six commercial vessels were contracted
on daily and trip bases. As of December 1, 2003, tags from 369 recaptured
fish were reported. Preliminary results indicate a low frequency of
movement between the Cape Cod grounds and Georges Bank. Six data-storage
tags have been returned, indicating distinct off-bottom movements. Five
high-value ($100) reward tags have been returned, and a $1000 lottery
reward was drawn in December. The movement-mortality model was developed
and tested using historical tagging data.
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| Results
from PSAT attachments to swordfish ... a
cautionary tale |
Session IV, Abstract IV-5
ORAL PRESENTATION |
Richard Brill1 and Michael
Musyl2
1NMFS/NEFSC, VIMS-HU CMER Program, Virginia
Institute of Marine Science, PO Box 1346, Gloucester Point, VA 23062
2NMFS/PIFSC, Joint Institute for
Marine and Atmospheric Research, University of Hawaii, 2570 Dole
St., Honolulu, HI 96822
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We
have deployed pop-up satellite archival tags (PSATs) on 28 swordfish
in the central north Pacific Ocean, as
well as on sharks (bigeye thresher, blue, oceanic white-tip, shortfin
mako), marlin (blue, black, and striped) and tunas (bigeye, yellowfin). The
objective of the project is to determine horizontal and vertical movement
patterns, and rates of survival following release from longline gear. PSAT
tethers were anchored with either nylon or metal tag heads (swordfish,
tunas, marlins, and bigeye thresher sharks), or attached to the dorsal
fin of sharks using a cable harness. PSATs were programmed to release
1, 2, 4, 8, and 12 months following deployment.
Early detachment has been
a continual problem in all species and we have found no attachment
method to be clearly superior. Overall,
less than 10% of the PSATs remained attached until their scheduled
“pop off” date. The average time PSATs remained on swordfish was 58
days (range 5-190 days). Non-reporting has also been an issue. Only
9 of the 28 PSATs (32%) attached to swordfish reported data, which
is about half the reporting rate for PSATs attached to other species.
PSATs have provided excellent
data on vertical movements, and swordfish have been shown to exhibit
a diurnal pattern. They are shallow at night
(less than .80 meters), but descend to .500-800 meters during the day.
(Bigeye thresher sharks and bigeye tuna show similar dawn and dusk
movements.) These behaviors, however, prevented the PSATs from providing
daily geolocation estimates. Either the low ambient light levels exceeded
the limits of the light sensor, or the changing ambient light conditions
caused by the fishes’ rapid crepuscular movements prevented the onboard
software from calculating times of dawn and dusk. Of the total days
at liberty, only 11% had daily geolocation estimates.
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| Monitoring the juvenile sandbar shark, Carcharhinus
plumbeus, population in the Delaware Bay nursery grounds |
Session IV, Abstract IV-6
ORAL PRESENTATION |
Camilla T. McCandless1, Nancy
E. Kohler1, and Harold
L. Pratt, Jr.2
1NOAA/NMFS/NEFSC, 28 Tarzwell Drive, Narragansett,
RI 02882-1152
2Mote Marine Laboratory, 24244 Overseas Summerland
Key, FL 33042 |
Delaware Bay is one
of the principal pupping and nursery grounds for sandbar sharks, Carcharhinus
plumbeus, in the East Coast waters of the United States. To provide
information for effective management of this essential sandbar shark
habitat, we need to understand and monitor its use by this species.
Researchers from the National Marine Fisheries Service (NMFS) and the
University of Rhode Island have been conducting gillnet and/or longline
surveys for juvenile sandbar sharks in Delaware Bay since 1995. In
2001, a random stratified sampling plan based on depth and geographic
location was initiated to assess and monitor the juvenile sandbar shark
population. The geographic regions and depth strata ranges were chosen
based on differences seen during historical sampling for juvenile sandbar
sharks in Delaware Bay by the NMFS from 1995 – 2000. Catch per unit
effort in sharks per hour was used to examine the temporal and spatial
relative abundance and distribution of sandbar sharks in Delaware Bay
during the summer nursery seasons. Population estimates of juvenile
sandbar sharks were also created using the catch data from the random
stratified sampling plan and an estimate of gear sampling area that
incorporates a simple Gaussian odor plume model. This model takes into
account the rate of odor production by bait and the chemosensory threshold
of the target species with respect to current velocity and gear saturation
time.
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