Warming Alaska waters may mean fewer crab, more predators

Submitted by Carin Bailey
Phone: (907) 322-8730
05/21/07

Gordon Kruse, a professor of fisheries at the University of Alaska Fairbanks, testified before the U.S. Senate earlier this month on how climate change is affecting Alaska’s fisheries.

Citing his own and others’ research, Kruse testified that rising ocean temperatures in the Alaska region are causing a dramatic shift in species distribution and a restructuring of Alaska’s marine ecosystems.

With nearly 60 percent of the U.S. total fish catch and some of the most productive marine ecosystems in the world, Kruse claims that higher temperatures in Alaska’s waters will have a profound effect on the globe’s most valuable marine resources.

"Alaska has seven of the top twenty U.S. seafood ports, including the highest seafood producing port-- Dutch Harbor-Unalaska," said Kruse. "Our waters also support thousands of marine mammals, millions of seabirds, and trillions of fish and shellfish that belong to hundreds of species."

Kruse cautions that Bering Sea crabs may fare poorly under global warming. Red king crab and snow crab in the eastern Bering Sea have shifted north since the early 1970s because of a preference for cooler water. This shift is reducing the survival of crab larvae because they are often too far north of productive nursery areas.

On the other hand, warming water temperatures are creating favorable conditions for some species of groundfish, such as pollock and Pacific cod.

"Unfortunately, some of the species that are responding well to global warming, such as arrowtooth flounder, spiny dogfish and Pacific and Jack mackerel, are species that prey on species that are highly valuable for Alaska’s commercial fishermen," said Kruse.

"Arrowtooth flounder not only eat our high-value species, but they are also species that have a low market value."

Kruse said that the warming trend in Alaska waters are also punctuated by temperature spikes from more intense and more frequent El Ni̱os that may provide windows into Alaska’s warmer future.

"Sightings of ocean sunfish and albacore tuna may become much more common in the future," Kruse said.

Rising water temperatures may also favor some commercial fishermen over others. For example, during last fall’s Bering Sea pollock fishing season, pollock were found farther north and west than usual. The larger, at-sea pollock fleet was better able to travel to the fish than smaller, shore-based fishing vessels.

Kruse also referred to recent research naming global warming as the cause of melting sea ice in the waters around Alaska.

"The loss of sea ice will have serious impacts on ice-dependent marine mammals, like polar bears, ring seals, bearded seals and walruses," said Kruse.

According to Kruse, one consequence of global warming will be greater uncertainty about future productivity of fish stocks.

"Under science-based management, increasing uncertainty translates into more precaution, which means more conservative fish harvests in Alaska."

Kruse’s testimony concluded with a recommendation for more research to better forecast and address likely changes in Alaska’s marine ecosystems.

Among his recommendations were suggestions for improved ecosystem monitoring, more process-oriented studies, increased climate-fisheries modeling and the expansion of ecosystem-based fisheries management.

Other members of the witness panel included Admiral James Watkins, co-chair of the Joint Ocean Commission Initiative; Lara Hansen of the World Wildlife Fund; David Conover, dean of Stony Brook University’s marine research center; Richard Feely, an oceanographer at NOAA; and Scott Doney, a senior scientist at Woods Hole Oceanographic Institute.

After the panel’s testimony, Senator Ted Stevens issued a press release encouraging increased research into the impact of global warming on fisheries. He also thanked panel witnesses.

"I would also like to thank our panelists and, in particular, Dr. Gordon Kruse, who has traveled all the way from Juneau, Alaska to participate in today’s hearing. Dr. Kruse has studied fisheries in Alaska for decades, most recently serving as chair of the Scientific and Statistical Committee of the North Pacific Fishery Management Council. Their committee plays a vital role in what the Pew Commission has stated is ’the best managed fishery in the world,’" said Stevens.

The UAF School of Fisheries and Ocean Sciences conducts world-class marine and fisheries research, education and outreach across Alaska, the Arctic and Antarctic. More than 60 faculty scientists and 135 graduate students are engaged in building knowledge about Alaska and the world’s coastal and marine ecosystems. SFOS is headquartered at the University of Alaska Fairbanks, and serves the state from facilities located in Seward, Juneau, Anchorage and Kodiak.