 Radio Script 2001
Alaska, Russian Salmon Getting Smaller INTRO: As biologists and fishermen search for the cause of Western Alaska salmon declines, scientists say the state's Yukon River chum salmon are getting smaller. What's more, it seems to be a trend affecting salmon returning to at least one river in Russia as well. Doug Schneider has more in this week's Arctic Science Journeys Radio. STORY: Chum salmon returning to Alaska's Yukon River and the Anadyr River in Russia have gotten steadily smaller since the 1960s. That's the conclusion drawn from a study of salmon growth done by state, university and federal researchers. Bill Smoker, a fisheries scientist from the University of Alaska Fairbanks School of Fisheries and Ocean Sciences, announced the study's preliminary findings at a scientific conference in Fairbanks late last week. SMOKER: "Our conclusions are that mature body size has declined in both of these histories over decades stretching back into the 1960s. These declines are the result of slowing growth in years three and four." Smoker, along with UAF researcher Milo Adkison and scientists from the National Marine Fisheries Service, the Alaska Department of Fish and Game and the Russian Pacific Fisheries Research Center, examined growth patterns in chum salmon scales collected since the 1960s from both the Yukon and Anadyr rivers. The Anadyr River lies almost directly across the Bering Strait from the mouth of the Yukon. Both rivers empty into the northern Bering Sea, a region that has seen dramatic declines in seabirds and marine mammals in recent decades. While scientists have in previous studies documented declines of as much as 30 percent in the body size of other Pacific salmon stocks, this is the first time scientists have been able to show a simultaneous decrease in the size of Yukon and Russian salmon stocks. Each year, Alaska fisheries managers collect thousands of scales from salmon to determine the age of returning stocks. Much like tree rings that grow thick in wet years and thin in years of drought, the rings found on salmon scales also can reveal growth patterns. Smoker says the rings representing the ocean stage of Yukon and Anadyr salmon became narrower since the 1960s, meaning salmon ate less and therefore didn't grow as big while foraging at sea.
SMOKER: "In both collections you could see the historical loss of body size continuing up through into the 1990s. We don't know much about the population numbers in the Anadyr, whether they've had the same kind of drastic fall in numbers that we've seen in the Yukon and western Alaska, but it is interesting that in general their growth patterns have been similar to those of the Yukon." Some scientists have attributed the smaller salmon to intense competition for food by too many wild and hatchery salmon on the high seas. In addition to the billions of wild salmon that each year migrate to the ocean, the U.S., Canada, Japan, and Russia release an estimated five billion hatchery-born salmon into the North Pacific Ocean. While Smoker says it's too soon to say just what's causing the decreased salmon size, he doesn't think salmon overcrowding is the problem. SMOKER: "It's tempting to attribute these declines to density interactions, because over the same years the density of Pacific salmon in the subarctic North Pacific has increased remarkably. But I'm skeptical because the declines encompass eras, years, decades, of both low and high density." Interestingly, Smoker says that while Anadyr River chum stocks have in recent years showed signs of improving growth in the year just before spawning, Yukon chums continue to suffer growing pains. Smoker says the problem with Yukon chum stocks may not rest with the Bering Sea, but rather the Gulf of Alaska. SMOKER: "One of the salient points here is that the ages at which chum salmon are experiencing slower growth are at ages two and three and four years. We believe those are years spent in the subarctic Pacific Ocean, outside the Bering Sea. So whatever has caused the decline seems to be affecting them in the North Pacific Ocean."
The researchers conducted their study with funding from the North Pacific Marine Research Program at the University of Alaska Fairbanks. Some 60 scientists met in Fairbanks to present findings from two years of research on fish, seabirds, marine mammals and oceanography of the North Pacific Ocean. OUTRO: This is Arctic Science Journeys Radio, a production of the Alaska Sea Grant Program and the University of Alaska Fairbanks. I'm Doug Schneider. Audio version and related Web sites (sidebar at top right) Thanks to the following individual for help preparing this script: William Smoker, Director Arctic Science Journeys is a radio service highlighting science, culture, and the environment of the circumpolar north. Produced by the Alaska Sea Grant College Program and the University of Alaska Fairbanks.
Alaska Sea Grant In the News The URL for
this page is http://seagrant.uaf.edu/news/ |
Listen to story on RealAudio Related Web sites North Pacific Marine Research Program (NPMR): Salmon Project A Basin-wide Retrospective Analysis of Growth and Survival Patterns in Pink and Chum Salmon Retrospective Analysis of Yukon River Chum Salmon Scale Growth (MS Thesis Research Progress Report by Tim Sands) Developing and deploying a high-resolution imaging approach for scale analysis (PDF file)
|
