PMEL Programs and Plans
Accomplishments in FY 96 and Plans for FY 97
Figures (a) Trajectories of satellite-tracked drifters deployed
during April 1996 in the Shelikof
Srait, Alaska Region, and
(b) Flight track of P-3 aircraft and surface chlorophyll
concentrations for May 1996.
Fisheries-Oceanography Coordinated Investigation
Accomplishments in FY 96
FOCI, one of a few marine fisheries
oceanography programs in the world predicting recruitment, made its sixth prediction
of pollock year class strength for Shelikof Strait: average recruitment for the
1996 year class. Component contributions were rainfall, wind mixing, advection,
and rough counts of larval abundance. This forecast for the first time used robust
empirical equations for rainfall and wind mixing relationships in contrast to
previous subjective determinations.
Current moorings and satellite-tracked drifting buoys deployed during spring
observed the weakest mean currents ever measured in Shelikof Strait and its sea valley. Flow in the sea
valley was dominated by a large, weak clockwise rotation; flow down the
strait was 5 cm s-1, in contrast to the more common 15 cm s-1. High concentrations
of larvae were observed during the first larval survey. Assimilation of these
data into FOCI's biophysical
model should provide insight into how pollock larvae survive under such
unique conditions.
The research basis for Shelikof Strait FOCI's first decade was documented in a special issue of Fisheries Oceanography (March 1996). Fourteen papers
synthesized and presented new results. These included: elucidation of formation
and maintenance of dynamics for larval patches, detection of mesoscale
biophysical features using novel acoustic techniques, and simulation of pollock
life history from egg to late larvae using a coupled physical, individual-based
model.
Bering Sea made the first
remote measurements of the progression of the spring bloom in the Bering Sea
basin using a technologically advanced, moored biophysical platform. During
spring 1996, the program augmented its knowledge of phytoplankton dynamics
by flying a NOAA P-3 research
aircraft equipped with an ocean color scanner over the slope and shelf.
Preliminary resultss show higher phytoplankton concentrations where the sea
ice is melting in the northern portion of the domain, and a prominent 100 by
200 km patch southeast of the Pribilof Islands with concentrations on the order
of ten times background levels. This patch is in a region that has been found to feature a large
spawning population of walleye pollock.
Using results from the genetic research component, historical surveys, and
outside expertise, the project has compiled a draft report on stock structure of
walleye pollock in the Bering Sea. Significant variation in mitochondrial DNA
allows differentiation of eastern and western Bering Sea pollock and inference
of potential gene flow between stocks.
Synthesis from five years of research defined two primary climatic modes for
conditions during summer on the Bering Sea shelf. Warm or cold shelf conditions
are indicated by the extent of seasonal sea ice in winter/spring and the
direction of wind over the shelf in April. Certain higher trophic level species
appear to vary in distribution on a multi-annual rather than interannual
temporal scale, e.g., the distribution for adult walleye pollock across the
shelf did not switch to the outer shelf during every cold year but only during
periods when cold conditions persisted for at least three years. The
distribution of age-1 pollock also varied with multiple cold or warm years,
changing from the outer shelf to the middle and inner shelf as conditions
warmed. Consequences of these two scales of variability must be considered when
evaluating species interactions on an ecosystem scale.
PMEL was selected to co-manage Southeast Bering Sea Carrying Capacity ( SEBSCC),
a 5-year, $1 million Coastal Ocean Program Regional Ecosystem Study. SEBSCC
will focus on two elements of the ecosystem: 1) cross-shelf transport and fate
of nutrients, and 2) juvenile pollock as a nodal species. A workshop was conducted
in November 1995 from which a review
document was produced and an announcement of opportunity developed. PMEL
is represented on 5 of 15 successful proposals: monitoring and development of
biophysical indices, circulation modeling, individual-based modeling of walleye
pollock, the role of atmospheric forcing on the "cold pool" and ecosystem dynamics,
and the influence of mesoscale eddies on the interaction of lower and higher
trophic levels.
Fisheries-Oceanography Coordinated Investigation
Plans for FY 97
- Conduct spring, summer, and fall research
cruises to the North Pacific, Gulf of Alaska, and Bering Sea supporting
physical and biophysical research for FOCI, Arctic Research Initiative, and
GLOBEC.
- Refine biophysical models for Shelikof Strait and eastern Bering Sea shelf.
- Forecast recruitment of 1997 walleye pollock year class for Shelikof Strait.
- Produce a recruitment studies summary report contrasting the affects of slope
and shelf habitat on survival of walleye pollock in the eastern Bering Sea.
- Provide access and analysis capabilites to Bering Sea data through the World
Wide Web.
- Develop a web-based theme page for communication between PIs and other
researchers interested in Bering Sea and North Pacific research.
- Synthesize knowledge of the physical environment of the Bering Sea shelf.
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