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Resource Ecology & Fisheries Management (REFM) Division

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July-Aug-Sept 2009
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Resource Ecology & Ecosystem Modeling Program

Ecosystem Ecology

Retrospective comparisons of zooplankton data and pollock diet data has begun. About 250 zooplankton sampling stations have been identified that are within reasonable temporal and spatial proximity (i.e., 7 days and 60 miles) to 85 stations where pollock diet information has been collected.

Fewer stations will be available with zooplankton community composition data to match with pollock diet information. Frequency differencing is being used to provide estimates of euphausiid backscatter density from AFSC hydroacoustic surveys through a NSF/NPRB Bering Sea Integrated Ecosystem Research Program (BSIERP) project.

During years prior to 2009, pollock stomachs were collected only from 14 trawl stations in the northern Bering Sea during the 2004 survey. Cursory examination of this data indicates no relationship between local euphausiid backscatter density and local pollock density.

Average stomach fullness as a percentage of individual pollock body weight (%BW) appears to be related more to the variation in copepod consumption than euphausiid consumption as indicated by the average amount of each prey type eaten per fish (g-prey/fish). However, all evidence suggests the overall abundance of euphausiids in 2004 was extremely low.

By Troy Buckley and Kerim Aydin


Ecosystem Modeling

REEM modelers attended weekly meetings with the BSIERP vertical modelers to continue development of the Forage and Euphausiid Abundance in Space and Time (FEAST) model, a 3-D model of the Bering Sea on a 10-km resolution, which will model the coupling between physics, plankton, forage fish, and predatory fish. The coupling between fish and plankton is bidirectional and includes feedback between these components.

Progress to date includes a fully coupled one-dimensional version (depth over time) producing expected growth rates and consumption for fish lengths 10 cm+ for 1999. The 3-D version of FEAST is fully coupled and ready for initial preliminary runs which will focus on refining movement parameters.

Milestones during the next 6 months include the completion of 1-year runs for 1999 (a cold year) and 2004 (a warm year). Results of the 1-D model were presented and discussed during a workshop hosted by the BSIERP's Fish Group.

This workshop, held in Seattle on 11-13 August 2009, focused on preliminary results of the fish projects, introduction to models and discussion of model outputs between modelers and field researchers. Updated results of the 1-D and 3-D models will be presented and discussed again at the annual BSIERP principal investigators meeting in mid-October.

By Ivonne Ortiz and Kerim Aydin
 

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