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Bering Sea chill yields fatter plankton, pollock diet changes

Date:
December 11, 2010
Source:
University of Alaska Fairbanks
Summary:
Despite a 30-year warming trend, the last three years in the Bering Sea have been the coldest on record. An Alaska scientist says that the cold temperatures have helped produce larger zooplankton in the Bering Sea, which may affect the way Walleye pollock feed.
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Themisto libellula.
Credit: Photo by Russ Hopcroft

Despite a 30-year warming trend, the last three years in the Bering Sea have been the coldest on record. A University of Alaska Fairbanks scientist says that the cold temperatures have helped produce larger zooplankton in the Bering Sea, which may be changing the way Walleye pollock are feeding.

Alexei Pinchuk, research professional at the UAF Seward Marine Center, has spent the last three years gathering zooplankton samples in the Bering Sea. He and his colleagues have been looking at how changes in temperature in the Bering Sea affect resident zooplankton, and in turn how those zooplankton shifts may affect the diet of Walleye pollock.

During colder years, like the last three, pollock tend to eat the larger zooplankton, like copepods and krill, which flourish in chillier temperatures. Pinchuk has also found that the recent cold temperatures have brought an arctic "sand-flea," the amphipod Themisto libellula, south into Bering Sea waters.Young salmon and pollock seem to prefer to eat these amphipods over other, smaller zooplankton.

In warmer years, which include the record-setting high temperatures of 2001 to 2005, smaller zooplankton tend to thrive. According to Pinchuk and his colleagues, younger pollock tend to eat the smaller plankton, while larger pollock favor the larger plankton found in colder waters. This causes younger pollock to start out doing well in warmer temperatures, but as the pollock grow bigger, they may not be able to find the larger zooplankton prey they need to produce enough fat for overwintering.

"The larger pollock may then eat their smaller cousins instead," said Pinchuk.

Pinchuk conducted his research on board the U.S. Coast Guard Cutter Healy, R/V Knorr and R/V Thomas G. Thompson. He collected his zooplankton samples using multiple collecting nets.

Although the last few years have been cold, scientists predict that the warming trend in the Bering Sea will continue.

Pinchuk's findings were recently featured in the Nov. 4 issue of the journal Nature. His work is part of the broad Bering Sea Project, a six-year, $52 million integrated ecosystem study of the Bering Sea. The Bering Sea Project" is funded by both the National Science Foundation and the North Pacific Research Board.


Story Source:

The above story is based on materials provided by University of Alaska Fairbanks. Note: Materials may be edited for content and length.


Journal Reference:

  1. Wendee Holtcamp. Marine science: The tiniest catch. Nature, 2010; 468 (7320): 26 DOI: 10.1038/468026a

Cite This Page:

University of Alaska Fairbanks. "Bering Sea chill yields fatter plankton, pollock diet changes." ScienceDaily. ScienceDaily, 11 December 2010. <www.sciencedaily.com/releases/2010/12/101209152801.htm>.
University of Alaska Fairbanks. (2010, December 11). Bering Sea chill yields fatter plankton, pollock diet changes. ScienceDaily. Retrieved May 24, 2015 from www.sciencedaily.com/releases/2010/12/101209152801.htm
University of Alaska Fairbanks. "Bering Sea chill yields fatter plankton, pollock diet changes." ScienceDaily. www.sciencedaily.com/releases/2010/12/101209152801.htm (accessed May 24, 2015).

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