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What scientists at the
University of Alaska Fairbanks say about salmon declines in Alaska Ted Cooney, professor of fisheries oceanography
Do salmon runs in the North Pacific Ocean fluctuate according to cycles? Cooney: "Scientific data on these natural cycles in salmon populations go back to the 1920s. These analyses show that for Alaska salmon stocks, there have been cycles in the past. The cycles seem to run on the order of 20 years. In some years more fish are produced and in other years fewer fish are produced. So, the recent declines aren't terribly surprising." Have scientists expected salmon returns to decline? Cooney: "There was speculation in the 1980s based on
research done here that salmon production might begin slipping in the
late 1980s and 1990s. That may be manifesting now in what appears to
be the collapse of the red salmon fishery, since the red salmon returning
this year were juveniles then." Milo Adkison, professor of fisheries Did you expect that salmon returns would be lower this year? Adkison: "Oh yes." So, the declines haven't come as a surprise to you? Adkison: "I didn't predict it would happen this year. But the idea that it was bound to happen eventually is pretty obvious to anyone who knows much about salmon and the history of the salmon fisheries." Explain what you mean by the history of salmon fisheries. Adkison: "The record of salmon returns is that they are highly variable. The salmon survival rates are highly variable. You get large year-to-year variations and you also get shifts in the productivity that run for a couple of decades or so and then shift to a different level of productivity. And it's all connected to changes operating on similar time scales on the ocean." Are state biologists to blame for not predicting lower salmon returns last year and this year? Adkison: "No. You know, my prediction was for about 38 million reds to return to Bristol Bay this year. ADF&G and the University of Washington predicted somewhat fewer fish. Based on the adult escapement, the smolt output, the returns of younger fish, and a look at some of the environmental variables used to predict, you would have predicted this would be a good year." So what went wrong this year? Adkison: "The conditions out in the ocean have been really unusual the last couple of years. It's not surprising that the models we use to make predictions fall apart when we encounter a whole new set of conditions. Generally, warmer sea surface temperatures are better for salmon. But the temperatures these past couple of years have been much warmer than what we've seen before. We may be going past the optimum to where warmer temperatures may actually be counterproductive for salmon. Is that what you think is happening now, that salmon are responding to long-term ocean cycles? Adkison: "I'm not saying that we've entered a new regime, but the problem is that you have shifts that occur every 15 years or so. On top of that you have this huge year-to-year variation. So it's really hard to look at a year like last year and say 'Okay, things were lousy this year and so they're going to be lousy next year.' It's very common to have things be lousy one year and good the next year. Because there's this large interannual variability, you have a hard time deciding that you're in a new regime until you've seen five years of bad returns in a row or five years of exceptional returns in a row." Should the environmental changes seen in the North Pacific Ocean last year, such as warmer water temperatures, seabird die-offs, and scarce plankton have tipped off managers that the salmon returns would be low this year? Adkison: "I wouldn't have thought so, but we have to take a look at that. The thinking among most fisheries biologists is that it's the youngest salmon that are the most vulnerable. So what you would have expected to see is a bad year out in the ocean and then a couple of years later a fall-off in salmon production, because the fish that had just gone to the ocean that year would be the ones most strongly affected. The adults due to come in that year could probably weather it better. So it's puzzling that the year the ocean conditions were a bit strange, the run failed the same year and not a couple years later." Are you going to adjust your salmon prediction downward for next year? Adkison: "I'm going to tell people not to trust any particular number that they see, because we really don't have a good idea what is going on." There seems to be a real lack of knowledge about what happens to salmon out in the ocean. How are scientists trying to get a better understanding of the role of the ocean on salmon abundance? Adkison: "The University of Alaska Fairbanks has been studying these questions as much as our funding permits. The Japanese are doing a lot out on the ocean looking at diets and distributions of salmon. NOAA has an ocean carrying capacity project where they're running around in the ocean too, following fish around to see what they are eating and what is available to them. I think people are trying to look at environmental conditions. They recognize their importance, and they are doing a fair bit to figure out just what environmental conditions are important. They're doing their best to come up with a better idea of what determines this variability." Why is this problem so difficult? Adkison: "The thing that holds us back is that it is real expensive and difficult to get out in the ocean to see what the fish are actually doing. They go throughout the North Pacific and the Bering Sea and they are very dispersed. It's a difficult and expensive thing to study." Fishery managers have come under fire for not considering the ocean's effects in their forecasts. Do you sense that fisheries managers are willing to take ecosystem influences into account in their forecasts? Adkison: "There's an increasing verbal focus on ecosystem considerations. But where the rubber hits the road there is a growing awareness that from a practical point of view it's very difficult to take an ecosystem approach to managing fish stocks. The data requirements are beyond what is available for most fisheries." Are there some key environmental variables that could be used to improve salmon return predictions without having to fully understand the entire ecosystem? Adkison: "People are doing the obvious things. They look at the abundance of principal predators; they'll look at the abundance of food; they'll look at indicators of the state of the overall ecosystem such as sea surface temperatures, weather patterns, and use them as empirical predictors of salmon survival. But it's still baby steps. About as much as you can do is add one or two components and hope that they improve your predictive ability." Tom Weingartner, assistant professor of oceanography Are you seeing environmental changes in the North Pacific Ocean? Weingartner: "It's a little hard to say what the time scales are, because there is a variety of time scales, but we have seen some rather striking changes in the last year or so. Last summer, we noticed an unusual warming that was confined to the surface layers of the Gulf of Alaska and the Bering Sea. Those temperature changes were two to three degrees above normal beginning about the middle of the summer and continuing through the fall. Beyond the fall, the temperature changes were even more dramatic. They weren't confined to just the surface but, at least in the Gulf of Alaska, they extended down at least 250 meters or so on the continental shelf. They were about two to three degrees above normal, and they continued through the spring. A lot of heat is required to elevate ocean temperatures by those few degrees. "Through the winter we noticed that there was a decrease in the amount of cooling that usually takes place in the Gulf of Alaska. That was very dramatic. Our Canadian colleagues have noticed in the Gulf of Alaska that nutrients necessary for phytoplankton production were depleted from the surface layers of the ocean. That has not been observed before in the Gulf of Alaska. Other things that have been noticed are a change in the phytoplankton species composition in the Bering Sea. That is usually dominated by a community called diatoms, but the last couple of summers it has been dominated by cocolithophores, a very different phytoplankton species." As an oceanographer who has witnessed such dramatic changes in the North Pacific Ocean ecosystem, are you surprised that the salmon returns have started to ebb? Weingartner: "Not being an expert in salmon per se, but knowing that the ocean does illustrate environmental changes from year to year, it's not surprising that the salmon populations might change in response to those changes." Are the changes we see the beginnings of a regime shift or an anomaly? Weingartner: "I don't have an answer to that question. Certainly over the last year we have been influenced by El Nino. Whether or not that is occurring in conjunction with a regime shift, I don't know. We really won't know that until we are into a regime shift for a while and are then able to identify it as such. All we can say is that there are some indications that we may be entering one." Are there connections to be made between the changes you see in the ocean and the smaller salmon runs? Weingartner: "It's important to note that just because we see some changes, the connection to salmon is not straightforward. In fact it is very difficult to say that the changes we observe are actually influencing salmon. Those connections have not been made. But they really need to be made to ascribe the reasons as to why salmon populations are down." Is our understanding of the marine ecosystem a field that is still in its infancy? Weingartner: "Yes, very definitely so--I think in large measure because many of the mechanisms, say temperature change effects on phytoplankton and how such changes are transmitted on up the food chain, are not well understood at all. Until those connections are understood, ecosystem management of, say, a salmon population would be difficult to make. Although I believe this is the direction we need to go, it won't occur overnight." Donald Schell, director Your research has focused on understanding the Bering Sea ecosystem and the role it played in the declines of Steller sea lions, seabirds and other species. Specifically, your work seeks to understand how the sea's production of plankton, the basis of the marine food chain, has changed over time. But to understand ocean productivity, you're studying bowhead whales. Please explain. Schell: "We've actually looked at bowhead whales to learn how ocean productivity has changed over the past 50 years. It turns out that whales are a unique window into the past. Bowhead whales overwinter in the Bering Sea, where they feed on zooplankton. Zooplankton are the first consumers of phytoplankton, the small plants that are the first rung of the ocean food chain and an important indicator of productivity in the ocean. These whales consume vast amounts of zooplankton. And also because they eat the zooplankton in the fall of the year, the zooplankton have themselves consumed and stored the energy of a large percentage of the ocean's phytoplankton productivity. This productivity can be measured by using isotope ratios in the baleen of whales. Without getting too scientific, I measured the type of carbon in whale baleen. Since you are what you eat, the carbon in this case is from the consumption of plankton. The changes in carbon type in whale baleen reflects the abundance of plankton in any given year and can be used as an index to changes in ocean primary productivity." And what have you discovered from looking at this record of ocean productivity? Schell: "If you isolate the portion of the baleen that reflects plankton eaten in the Bering Sea, you can see the changes that occur over time. We've studied baleen taken from recently harvested whales and from whales harvested in the 1960s and the 1970s. And by using the animals from the 1960s we can look all the way back to 1946. From this we have developed a record of phytoplankon productivity in the Bering Sea all the way back to 1946. The story it tells is amazing because the whale baleen reflects phytoplankton productivity quite well. The record shows that from 1946 to 1963 everything went along fairly smoothly at a relatively high rate of productivity. And then in the mid-1960s it increased and peaked at around 1965. Then ocean plankton productivity began to decline, and since the mid-1970s it has gone down and down and down. The last samples we have from 1994, 1995 and 1996 show the lowest primary productivity in the Bering Sea over this 50-year period." What conclusions can you draw from this finding? Schell: "The implication is that the Bering Sea has decreased in productivity by 35 to 40 percent since its peak in 1965 or so. Now a 40 percent decline in the carrying capacity of the ecosystem is going to have profound effects on the top consumers, and I think that is in part what we are seeing now. Salmon are near the top of the consumer chain. Steller sea lions are at the top and they eat salmon and other fish. It implies that there is indeed a bottom-up change that is occurring, and it may have contributed to the decline of these mammals and other Bering Sea species."
Andy Golia, of Dillingham, Alaska, is the winner of the 1999 Bristol Bay Sockeye Return Forecast Contest! His guess of 15 million sockeyes for harvest in 1999 comes the closest to the Alaska Department of Fish and Game's official forecast of 13.8 million harvestable sockeyes. ADF&G's forecast was released November 25, 1998, and published in the Anchorage Daily News. What has Andy won???? Why, he's won a $50 gift certificate redeemable on books, posters, videos and many other fine gifts at the Alaska Sea Grant online bookstore. Well done, Andy!
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