National Oceanic and
Atmospheric Administration
United States Department of Commerce


FY 2014

Fish forage distribution and ocean conditions

Hollowed, A.B., S. Barbeaux, E.D. Cokelet, S. Kotwicki, R. Lauth, P. Ressler, P. Stabeno, and C. Wilson

NPRB BSIERP Project B62 Final Report, North Pacific Research Board, 416 pp, Available online at (2013)

This report summarizes the scientific achievements of Project B62 and B91. This report serves to also be the final report for the in-kind project B91 (which is not formally required to have a stand-alone report).

State-of-the-art statistical methods were applied to estimate the functional responses of forage fish and commercial fish to changing climate. Analytical frameworks were developed to project these relationships forward under different climate change scenarios. Innovative new methods were introduced to collect oceanographic and biological data in the eastern Bering Sea. These new methods provided valuable new insights into the impacts of climate variability and change on the spatial distribution, abundance and species interactions in the region. The oceanographic observations provided new data on: water column properties (temperature and salinity), depth, chlorophyll a, oxygen, nitrate, and sea surface temperature. Water column profiles revealed a latitudinal gradient in the upper to lower density difference with stronger stratification north of 59°N. In spring, near surface chlorophyll a, oxygen and nutrient data exhibited relationships consistent with the classical Redfield ratios. Oceanographic conditions were cold throughout the study period which inhibited our ability to compare the strength of density gradients across the shelf in warm and cold years, however, we were able to show that the boundary of the well-mixed, inner shelf was not always located at the 50m isobath. The new data sets were utilized by the BEST-BSIERP modelers to groundtruth coupled biophysical models.

National Marine Fisheries Service standard surveys were augmented to provide new biological observations including: euphausiid vertical and spatial distribution, spatial and vertical distribution of walleye pollock combined from bottom trawl and acoustic surveys, and winter pollock spawing distributions. Retrospective studies showed strong evidence of niche partitioning amongst forage fish, and juvenile and adult groundfish. Depth alone was not sufficient to explain these distributions, light, bottom temperature, prey availability (euphausiids) and predator abundance were all selected as explanatory variables. Comparison of acoustic estimates of euphausiid and juvenile and adult pollock distributions showed evidence of top-down and bottom-up forcing but overall water temperature was a much stronger predictor of euphausiid biomass than pollock biomass (a proxy for predation pressure). The functional responses derived from retrospective studies served as a foundation for the formulation of coupled bio-physical models of the Bering Sea. The projection modeling framework provided a the first quantitative estimate of expected changes in sea surface temperature and wind under future climate change as well as the expected impact of these changes on the cross-shelf advection of northern rock sole larvae and juveniles. This project contributed to 22 peer reviewed publications and 69 oral presentations at scientific conferences.

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