A euphausiid under the microscope. |
Project
Overview
The goal of this
project is to develop improved mathematical models of the Target
Strength of Bering Sea euphausiids. These models are needed to improve
the accuracy of acoustic estimates of krill and fish biomass done in
the Bering Sea. As part of this research, we participated in a pollock assessment research cruise aboard the RV Oscar Dyson conducted by the MACE program at the Alaska Fisheries Science Center which is part of NMFS. The Research Team
measured several parameters of live euphausiids which will be used as
input data for the scattering models. In addition to the shape and mass
of the animals, we focused on measuring the density and sound speed
of the animals which have a large effect on how much sound they
scatter. In addition to the euphausiids, we also collected measurements
on several other types of zooplankton found in this region including:
copepods, amphipods, jellyfish, siphonophore bracts, fish larvae, and
pteropods. Funding for this project is from NOAA and the NPRB ???.
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The Research Team
SoMAS Professor Joe Warren and graduate student Joy Smith are the
research team for this project and we're working with Dr. Patrick
Ressler at the Alaska Fisheries Science Center.
Joe is a bioacoustician who is interested in improving our ability to
convert acoustic backscatter data into biologically meaningful
information. Joy's thesis project will be based (in part) on the data
collected during this cruise. While leaving Long Island in the summer
for a month was difficult to do, the opportunity to travel to Alaska,
sail out of Dutch Harbor (the home port of "Deadliest Catch"), and
participate in the pollock stock assessment cruise were too much of an
opportunity to pass up. In three weeks at sea we collected a multitude
of data on several euphausiid species as well as other zooplankton. We
are working on the analysis of these data post-cruise and will be
presenting our preliminary results at a science symposium in Anchorage
in January 2009.
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Joe and Joy help process the pollock trawl catch. |
A pollock and its stomach contents including zooplankton. |
Pollock and zooplankton
Walleye pollock is the largest fishery in the United States (in
terms of landings, that is lbs of fish caught) and accounts for roughly
1/3 of all fish landings in the US. So why have you not seen pollock on
your restaurant menus ? The majority of pollock is processed and made
into fish sticks, fast food fish sandwiches, and surimi (imitation
crabmeat). Annual surveys (using acoustics and net trawls) are used to
estimate the Bering Sea pollock stocks which in turn are used to set
fishery catch limits. We're interested in zooplankton in these waters
for two reasons: acoustically and ecologically. Acoustically,
zooplankton scatter sound and may cause uncertainty in the acoustic
estimates of pollock stocks so better understanding how zooplankton
scatter sound can improve the assessors ability to differentiate
between zooplankton and fish schools in the water column. Ecologically,
zooplankton serve as a primary food source for many of the fish
(including pollock) in these waters as well as other animals such as
baleen whales, seals, and sea birds.
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