How should we manage Alaska's fisheries in the face of warming oceans? Answers to that question were hard to come by among scientists gathered last week for the Wakefield Symposium in Anchorage. The most solid scientific information came from a bird biologist.
Fish biologists attending the Wakefield Symposium in Anchorage last week are struggling to find answers to such questions as: Why are the king salmon are coming back younger and smaller with more young male jacks?
The scientists suspect that it is related to our warming oceans and climate change, but they don't have any clear answers yet. Scientists like Jan Ohlberger with the University of Washington are ready to discard old ideas, like the hypothesis that directed fishing for large male king salmon on popular sport fishing rivers like the Kenai is responsible for the decline of the big trophy kings. He looked at Alaskan fish throughout the state and saw the same trend.
"When we look at the older ocean ages, they all decline in size," said Ohlberger. "There's actually very little variability in a given state. They all follow this declining trend."
Jared Siegel at the University of Alaska Fairbanks has been studying the returns in a couple of Southwest Alaska rivers that are not heavily fished by anyone, and he found that warmer sea temperatures resulted in faster growing, but smaller, males.
"We had smaller, younger males, or jacks, in these populations that were maturing at smaller sizes at warmer temperatures. And this appeared to create a stronger relationship in males, while all of our other measures for females and older males were largely independent of temperature," said Siegel.
Siegel suggests that warmer oceans may mean that Alaska's fish will become more like stocks down south that mature younger and smaller.
The question for scientists remains whether these results are limited to ocean conditions, or if they are also set up by changes in the rivers where Chinooks spend their first year before heading out to sea. Biologist Katherine Miller with the National Ocean and Atmospheric Administration spent three years looking at king salmon on the Yukon River.
The three years were very different. The first was cold, but the ice melted slowly away with no chaotic spring breakup. The second was warmer, and the third year was just plain hot. She found that the fish looked the same, but had different amounts of energy, or fat levels, in them at the end of the year to help them survive at sea. But that didn't really tell Miller anything about what is "normal".
"I don't think I know what's normal," she said. "There has been a huge amount of variability: variability in catch, variability in size, variability in environmental conditions."
Fish biologists have not done the research needed to know what is normal in a species like salmon that experiences huge fluctuations in run size, and migrates between ocean and river systems.
Scientist do know that salmon in the north have a different temperature tolerance that salmon populations down south.
"So we're seeing these higher temperatures, and the question is really adaptation," said Miller. "Can our fish adapt? A southern fish may be able to get to 20 degrees Celsius or 24 degrees Celsius. Can a Yukon River fish? These are cold water adapted fish."
That's one of the reasons Miller thinks it's important to look at the young, tiny kings in the rivers, especially a large and long river like the Yukon. She had hoped to continue the study, but does not have the funding.
Most of the money in fisheries research is centered on something called recruitment: how many of the young fish, or spawning biomass, become adult fish that can be harvested. This work is centered on big money species like pollock and crab. The assumption is that the larger the spawning biomass, the more recruitment. But with the oceans warming and conditions changing, it has become clear that there is no real relationship between the two. Even the people that make models from fisheries data are now saying it would be better to look at how the fish are growing, because that reflects the marine environment and whether the fish are getting what they need.
Here is where bird biologist Doug Causey comes in. He has been conducting an isotope study in the Aleutian subarctic and in the Greenlandic high arctic. By looking at the isotopes in various bird species, he can find out what they have been eating and look further down the food chain to what the bird's prey have been eating.
The maps he presented comparing the isotope studies done in 2000 with the ones he is working on in the Greenlandic high arctic reveal a rapidly unraveling and disintegrating marine food chain.
"The food-web structure is destabilized. It's very likely in a transition, very likely going to go to another stable confirmation, but it is not what was," Causey reports. "Over this brief amount of time, food-webs in the high arctic and in the low arctic are getting an increasing variance, which means it is getting harder to predict. The food-web is decreasing in complexity and the rapid fine-scale decline is species diversity and richness. The largest effect is seen in the high arctic, but the low arctic shows the same pattern."
Most of the scientists at the Wakefield Symposium did not realize this was happening.
Change is occurring so quickly in the oceans that scientists don't really understand it. The approach used by federal and state fisheries managers assumes an environment that is fairly stable. That doesn't seem to exist anymore, those assumptions no longer reflect the reality, and it's not clear what scientists can use instead. The only thing that is clear is that fish biologists, the managers that depend on their understanding, and the people who depend on the fish are in for a wild ride as the oceans warm, especially if the rate of warming continues to increase.
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