Too many hatchery raised salmon?
While environmental groups and media in British Columbia are focusing most of their energy on blaming the province’s salmon farming industry for any kind of down-turn in the numbers of salmon returning to spawn in B.C. rivers, the state of Alaska is taking a more broadly focused approach. After years of declining returns of Chinook salmon to its rivers, government officials and others are questioning the effect that hatchery-raised salmon might have on the well-being of wild salmon. Alaska will in a typical year produce some 1.5 billion juvenile salmon that are released from hatcheries and into the ocean- perhaps to compete for a finite food supply. British Columbia adds another ~500 million, and Japan and Russia billions more. Add to that the fact that the climate patterns are changing, and one might find other reasons for fluctuations in salmon stocks than fish farms.
Margaret Bauman from The Cordova Times reports from a recently completed meeting of minds organized to look at the issue of declining Chinook salmon returns in Alaska, where scientists agreed that more effort is needed to assess risk of climate change and hatcheries to wild salmon stocks;
Abundance of salmon in the North Pacific Ocean is the highest it's ever been, but fisheries scientists say there are many unanswered questions about how many fish the ocean can feed, particularly in light of climate change. "I'm coming at it from the standpoint of limited ocean carrying capacity for salmon, and that changes all the time, depending on climate and all the other factors," said Kate Myers, a retired University of Washington professor who was a panelist at the recent Alaska Chinook Salmon Symposium in Anchorage. "I don't think we really understand how carrying capacity is fluctuating with climate change, but it is an important topic for research," she said. "Some scientists want a more international focus on this issue. Stocks from many countries are overlapping." "The North Pacific has more Pacific salmon in it now than it has in the last century," agreed Daniel Schindler, a professor in UW's School of Aquatic and Fishery Sciences, who also attended the Chinook (king) salmon symposium.
Both Myers and Schindler made their comments in interviews in late October. Most of those salmon are pinks and chums, with many of the chum salmon coming from Japanese hatcheries, while most of the pink salmon are coming from wild and hatchery stocks on this side of the North Pacific. Russia meanwhile plans to put more pink salmon into the ocean from hatcheries in the area of Sakhalin Island. "The ramp up in hatchery production has occurred mostly since the mid 1970s and that has coincided with the North Pacific Ocean being in a very productive phase for salmon, so the more smolts put out there, the more that came back," he said.
The unanswered question is how climate change and Pacific Decadal Oscillation (PDO) will affect salmon stocks, including the prized king salmon. Pacific Decadal Oscillation is a pattern of Pacific climate variability that shifts phases on at least inter-decadal time scale, usually about 20 to 30 years. The PDO is detected as warm or cool surface waters in the Pacific Ocean, north o f 20 degrees north. During a "warm" or "positive" phase, the west Pacific becomes cool and part of the eastern ocean warms. During a "cool" or negative phase, the opposite pattern occurs. "There are good indications that the North Pacific is starting to slide back into a slow phase, a cool PDO phase," Schindler said. "When it is in a cool phase it is not so good for Alaska salmon."
So when ocean conditions are not as good for salmon, how does ocean carrying capacity change? Should hatchery production be adjusted? That's an unanswered question. Another unanswered question is how hatchery salmon compete with wild fish. While hatcheries have the potential to assist in the conservation of wild stocks, they also pose some risks, biologists from the NOAA Northwest Fisheries Science Center noted back in September 2006. "At this time, scientists still have many questions about the extent to which hatchery programs enhance or threaten the survival of wild populations. Additional research and investigation is needed."
Salmon conservation is important for biological, economic, cultural and religious reasons, the NOAA biologists noted. "When salmon return to their natal streams to spawn and die, they bring large amounts of nutrients from the marine environment into rivers and streams, where they enrich both plant and animal life. Salmon are also part of Native American spiritual and cultural identity. And the harvest of salmon by commercial and sport harvesters is an industry worth billions of dollars. The elements of a hatchery system for Pacific salmon started developing in the late 19th century. Hatcheries currently contribute between 70 percent and 80 percent of fish in coastal salmon and steelhead trout areas in the Pacific Northwest. Over the past several decades, wild salmon populations have declined dramatically, despite and perhaps sometimes because of, the contribution of hatcheries.
With this decline has come an increased focus on the preservation of indigenous wild salmon stocks. Hatcheries improve the survival rate of young salmon (eggs, fry and juveniles). More young salmon survive in the hatchery than would survive in the wild where there are no predators in hatcheries, food is abundant, and the environment is relatively constant. Wild salmon have existed for millions of years, and Pacific salmon, as we know them, emerged about 2 million years ago. Because salmon typically spend between one and three years in the ocean before returning to their natal streams to spawn, ocean conditions impact salmon survival and growth.
Remaining natural salmon populations, NOAA scientists said, "provide the best chance for long-term survival of salmon because they have had to evolve and respond to significant environmental changes over many thousands of years, and can be expected to do so in the future. While wild salmon populations have existed for many thousands of years, most hatchery populations have only existed for several decades, or less. "We do not know if hatchery stocks have the same resilience as wild salmon populations," the NOAA scientists said. "If hatchery stocks can't survive on their own in the wild, they will need a hatchery to sustain them forever."
This can be problematic, they said, because mechanical and technical difficulties occur periodically in hatchers, and hatcheries are expensive to operate, requiring a large and constant source of funds. According to Schindler, hatcheries tend to select for fish who are very aggressive feeders. These salmon are often resistant to hatchery diseases. In a hatchery, you have much more uniform conditions and avoiding predators is not a selected trait (by these salmon), but resisting disease and being aggressive feeders may be, he said. "We have assumed hatcheries can replace natural habitat, but places like Alaska have increasing demands for other uses of watersheds. We don't want to assume hatcheries can replace viable productive habitat (for salmon)," he said.
