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Recruitment Processes Program

Summer Field Season

Figure 9 map, see caption
Figure 9.  Location of stations occupied during the fall eco-FOCI
        cruise aboard the NOAA ship Miller Freeman, 4-16 September 2007.

The Recruitment Processes Program had a busy summer field season. During 4-16 September, the program participated in NOAA’s Ecosystems & Fishery Oceanography Coordinated Investigations program (Eco-FOCI) cruise in the Gulf of Alaska (GOA) aboard the NOAA ship Miller Freeman.

The cruise was conducted to collect the necessary data to rigorously evaluate the relative quality of food available to juvenile walleye pollock in two important nursery areas (Fig. 9), and to begin to address the potential for prey switching by arrowtooth flounder that may act as a density-dependent community stabilizing mechanism, if it occurs. The data collected will also extend a time series established by the program that may be useful as a pollock recruitment predictor. Walleye pollock is a major component of the GOA groundfish fishery and marine ecosystem.

Data and samples were successfully collected at each of 68 predetermined survey grid locations. Environmental and zooplankton data were also collected at each station. The Stauffer (a.k.a., anchovy) net was used to collect small midwater fishes, which were sorted on deck (Fig. 10 below). A total of 2,600 walleye pollock were measured (Fig. 11 below), and many were preserved for subsequent determination of age and diet. The vast majority of the juvenile walleye pollock were collected from the Semidi grid, which indicates that it is a more heavily used nursery than is the area encompassed by the Kodiak grid. The number of juveniles collected was low relative to other years in the time series.

Figure 10, Gary Cooper with catch of walleye pollock
Figure 10.  Gary Cooper helps dump a catch of walleye pollock onto the sorting table.  Photo by Ingrid Spies.

Figure 10, juvenile walleye pollock
Figure 11.  Ingrid Spies holds a juvenile walleye pollock while coworkers collect biological information.  Photo by Ingrid Spies.

Additional sampling at seven grid locations was conducted using a bottom trawl to collect arrowtooth flounder, which were dissected at sea to facilitate visual scan of stomach contents. Acoustic data were collected continuously at 18, 38, and 120 kHz using the Simrad ER60 (APC 10) echo sounder. Personnel in the AFSC Food Habits and MACE Programs provided gear and consultation necessary for the successful collection of the stomach scan and acoustic data.

The Recruitment Processes Program had several other cruises in the Bering and Chukchi Seas. Kevin Bailey, Morgan Busby, and Colleen Harpold joined our colleagues from Hokkaido University to sample the eastern Bering Sea shelf for zooplankton, ichthyoplankton, and juvenile fishes aboard the Japanese research vessel Oshoro maru. This is our tenth year of cooperation with Japanese scientists on this annual cruise.

We also collected plankton samples aboard the F/V Arcturus in collaboration with the RACE Groundfish Assessment Program (GAP) during the summer eastern Bering Sea bottom trawl survey. One sample was collected each day after the final trawl of the day.

AFSC scientists Jay Clark collected samples during Leg 1 (June) and Elizabeth Logerwell collected samples during Leg 2 (July). Both worked along side GAP personnel to process trawl catches the majority of the time. Morgan Busby also participated in the Auke Bay Laboratories’ Bering and Aleutian Island Salmon International Survey (BASIS) survey of the Chukchi Sea aboard the Oscar Dyson (August –September). This was a new opportunity for the Recruitment Processes Program to obtain and study larval fishes from areas much farther north than our usual collections areas.

Recruitment Processes, as part of the North Pacific Climate Regimes and Ecosystem Productivity (NPCREP) project, a collaboration with NOAA’s Pacific Marine Environmental Laboratory, staged an 18-day cruise aboard the University of Washington’s research vessel Thomas G. Thompson to survey fall conditions in the eastern Bering Sea. Samples were taken on four cross shelf transects from the southeastern shelf to just south of St. Lawrence Island, and approximately 50 stations along the 70-m isobath were occupied and sampled from St. Lawrence Island south to mooring site M2.

This is the third year that NOAA has sampled these stations in spring and late summer. We now have data from a warm year when sea ice coverage in spring was minimal (2005), a year of cool conditions and increasing ice (2006), and a cold year with moderate winter and spring ice coverage (2007). The data resulting from these cruises is being used to understand the role of sea ice in this ecosystem and to help predict how the eastern Bering Sea ecosystem may respond if the area experiences further warming and reductions in seasonal sea ice.

By Matthew Wilson

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