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Recruitment Processes Program

Eco-FOCI Fall Juvenile Fish Cruise, Gulf of Alaska

figure 1, see caption
Figure 1.  Collection site locations occupied during 1-14 October 2011.  Symbols identify which cruise objectives or activities were addressed at each site.

Scientists from the Recruitment Processes program studied juvenile walleye pollock and flatfishes in the GOA during autumn 2011 aboard the Oscar Dyson. Predetermined collection sites formed grids over the continental shelf near Kodiak Island and between Shelikof Strait and the Shumagin Islands (Fig. 1).

The cruise objectives were to 1) extend a time series of age-0 walleye pollock abundance at index sites within the Shelikof-Shumagin area; 2) test the utility of resource selection models (RSM) for predicting site-specific presence of flatfish over the continental shelf; and 3) collect samples of the potential prey taxa of juvenile fishes.

The time series is currently being evaluated by scientists for its ability to predict pollock recruitment in the GOA. At the time-series sites, the frequency of age-0 walleye pollock occurrence in midwater was 85% (22 occurrences at 26 sites).

Preliminary mean abundance at these sites, not corrected for possible diel effects on catch, was higher in 2011 than in 2001, 2003, 2007, and 2009, but lower than in 2000 and 2005. The average standard length of all measured age-0 walleye pollock was 82 mm (n=1,322, size range = 52 127 mm).

Data on juvenile flatfish presence, sediment composition, and environmental conditions were collected at 35 sites to examine the utility of RSM for predicting the presence of juvenile flatfishes on the continental shelf of the western GOA. Potential prey of midwater and benthic juveniles was sampled at nine sites to examine the possibility that specific geographic areas may offer favorable feeding conditions for a diverse assemblage of juvenile fishes.

At nine other sites, the seafloor was too rough to sample on bottom so only a midwater sample was collected. This additional sampling was to supplement collections made for the North Pacific Research Board-sponsored GOA-Integrated Ecosystem Research Program and for a study of otolith element composition. Two oceanographic moorings were recovered and one was deployed in the vicinity of Chiniak Gully. Analysis of the data and samples is currently underway.

By Matt Wilson

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