So suggests a team of West Coast fishery scientists.
Their hypothesis flips on its head the idea that the problem is the Chinooks (kings) killed at sea by trawlers and suggests that the humpies (pink) and dog (chum) salmon pumped into the ocean by salmon ranchers in Alaska, Japan and Russia are more important.
The study would indicate that Alaska salmon ranching, which was largely state funded in the beginning, might play a part in helping to over-stuff the ocean with hungry pinks and chums that so efficiently gobble up available food that survival rates plummet for Chinook salmon, which in good years help to feed a lot of low-income Alaskans along the Yukon and Kuskokwim rivers in Western and Central Alaska.
“It sure doesn’t surprise me,” Dave Cannon, a fisheries biologist living the small village of Aniak on the Kuskokwim, said Sunday. One of about 500 residents there, he cautioned, however, “that trying to definitively prove this stuff is difficult.”
Powerful political and business interests tied to the state’s private non-profit (PNP) hatchery system are sure to challenge the research, Cannon said. Those hatcheries have been a good investment for fishermen who have in recent years paid assessments to help fund them.
They got their money back and more. According to the Alaska Department of Fish and Game, the PNP hatcheries in 2017 put an estimated $331 million into the pockets of commercial fishermen.
On a purely fiscal level, the hatchery program begun by the Fisheries and Rehabilitation and Enhancement Division of Fish and Game during the 1970s salmon crash has been a rousing success.
The entire, statewide salmon harvest in 1973 and 1974 was 22 million fish per year. The 25 PNP hatcheries run primarily to benefit commercial fisheries now produce a catch more than twice that size. Forty-seven million hatchery pinks were caught last year despite what were considered mediocre hatchery returns.
Subsistence, personal-use and sport fishermen did catch some PNP fish, but at 196,000 last year their harvest amounted to less than half of a percent. And what they lose because of the hatcheries might exceed what they gain.
In a peer-reviewed paper published Wednesday in Marine and Coastal Fisheries – Dynamics, Management and Ecosystem Science, researchers Gregory T. Ruggerone from Seattle and Jim Irvine from Nanaimo, British Columbia, Canada, suggest the huge production of hatchery chums and pinks could be depressing wild populations of both kings and silvers (cohos), the most prized sport fish in the 49th state.
“In Alaska, declines in size at age and abundance of Chinook salmon and coho salmon and a decrease in age at maturation in Chinook salmon may be related to the alteration of the food web by highly abundant pink salmon and higher mortality during late marine life,” they write.
“Salmon abundance in large areas of Alaska (Prince William Sound and Southeast Alaska), Russia (Sakhalin and Kuril islands), Japan, and South Korea are dominated by hatchery (pink and chum) salmon. During 1990–2015, hatchery salmon represented approximately 40 percent of the total biomass of adult and immature salmon in the ocean.”
Hatchery costs
Ruggerone and Irvine were joined by six other West coast scientists in preparing another paper suggesting hatchery pinks might be altering the entire North Pacific ecosystem and contributing to Chinook declines. They presented at the 19th Salmon Ocean Ecology Meeting in Newport, Ore. in February.
The paper went a step beyond the earlier work in pondering whether hatchery pinks started a “trophic cascade” affecting seabirds, Chinook and coho salmon, plankton and possibly even sockeye salmon. Trophic cascades are changes, usually predation related, that ripple through an ecosystem from top to bottom.
Wolf removal is the classic ecological example: Wolves are eliminated. Deer populations explode. Hungry deer denude the forest understory. The loss of the understory creates a desert beneath the trees with implications that penetrate all the way into the soil which affects the trees above.
The theory as regards hatchery fish is similar but somewhat opposite. Instead of predators being removed, they are added. The results, as outlined by Ruggerone and others in their hypothesis, are these:
- Boosted by hatchery pink, chum and sockeye, North Pacific Ocean salmon stocks increased to historically high numbers.
- All those salmon, especially pink salmon, eat so much they alter the food chain in ways that reduce prey for Chinook and coho salmon.
- Food shortages lead to reduced growth of Chinook and coho at sea.
- Reduced growth translates into higher ocean mortality, especially of females, and a return of smaller-sized Chinook spawners with a lower ratio of females-to-males for both Chinook and coho.
Fisheries biologist have long known the importance of ocean survival for salmon, a species stalked by death from egg to adult. A 2007 study of chums in the Kwethluk River of Western Alaska estimated 56 million eggs were spawned there that year, but only about 2.9 million chum salmon fry made it to the ocean a year later.
About 95 percent died as eggs or alevins in the gravel of the river or as fry after emergence. Still, there were 2.9 million going to sea where every percent change in marine survival could make a big difference.
A 1 percent improvement or decline would equal 29,120 fish; a two percent improvement, 58,420; a three percent improvement, 87,360. And a study of wild pink salmon at Auke Creek near Alaska’s capital city of Juneau found marine survival varying from a low of 3.6 percent to a high of 29.7 percent over the course of 14 years, thus illustrating the nearly tenfold importance of what happens at sea.
With Alaska Chinook runs weak in recent years and no obvious reasons for increased freshwater mortality – Alaska hasn’t built any major dams or started any major mines or boosted agriculture – biologists have been increasingly looking to the ocean for the cause of the Chinook decline.
But to date, only limited attention has been paid to possible hatchery influences on Chinook survival. The preoccupation has been with Chinook by-catch in dirty trawl fisheries.
Easy target
Battles over the indiscriminate nets dragged beyond offshore trawlers have raged for years. Trawlers mine the sea for more than 2 million metric tons of bottomfish per season. The catch is worth about $1 billion per year, and most of the profit goes south to the Pacific Northwest.
Were that not enough, the trawlers drag up and kill a significant number of Chinook and highly valuable halibut in the process of catching those tons of pollock, pacific cod and rockfish. They accidentally snared about 61,000 immature Chinook last year, according to National Oceanic and Atmospheric Administration Fisheries.
Trawlers are prohibited from keeping those fish. Most of the catch goes to Seashare, a Seattle-based non-profit organization that distributes seafood to the nation’s poor. But despite the prohibition on profiting from Chinook and the donation to the poor, trawlers are easy for Alaskans to hate given the kings they kill and the profits they make.
The trawl by-catch represents less than 10 percent of the total Alaska catch of Chinook, most of which is taken in the commercial and subsistence fisheries. Still even a little matters a lot to many in a state where kings are both prized and worshipped.
When king salmon runs faltered on the Kuskokwim in 2012 and fishing closures were ordered, a civil revolt arose. Alaska Natives claimed their culture couldn’t exist without fishing. Many put out their nets in violation of the closure and about two-dozen ended up charged with illegal fishing. Most went to court to fight the charges.
A bunch wanted to see an end to trawl by-catch, a goal just about impossible to achieve without shutting down the fishery that provides the main ingredient for McDonald’s Filet-O-Fish.
And the Filet-O-Fish, according to Business Insider, is “one of President Donald Trump’s favorites….He’s known to put away two of the fish sandwiches at a time, along with two Big Macs and a large chocolate shake.”
Even before Trump’s arrival in the White House, however, the less than 30,000 people of Western Alaska didn’t have much chance of shutting down a $1 billion business with deep political connections.
The Bethel-based Association of Village Council Presidents, the Fairbanks-based Tanana Chiefs Conference and about 100 Alaska Native tribes (almost every village in the state is a tribe) did petition federal authorities to reduce the by-catch of Chinook in the Bering Sea by two-thirds in 2014, but got nowhere.
It was noted then that the question of what has reduced king salmon numbers is a difficult one, and that simply blaming the trawlers might be oversimplifying things. The ocean ecosystem is extremely complex given that prey often grow up to become predators in a system where everything pretty much eats everything else and the only constant is that the bigger fish eat the smaller fish.
The latest studies raise almost as many questions as they answer about what goes on beneath the surface of the sea, but two of the Ruggerone and Irvine observations should be particularly interesting and possibly a little troubling for Alaskans.
The first is that “total adult (salmon) biomass—and especially adult plus immature biomass—has been relatively stable from 1993 through 2015, suggesting that the carrying capacity of the ocean may have been reached during the post‐1977 regime,” Ruggerone and Irvine write. “This finding leads to the question: Would natural‐origin salmon rebound if hatchery production was significantly reduced?”
It also leads to another question: Will adding yet more hatchery fish increase overall production or only depress wild Alaska salmon runs?
The second observation in the Ruggerone and Irvine study is, however, the troubling one. Alaskans who fish – be they commercial, subsistence, personal-use or sport fishermen – have benefited greatly from the North Pacific warming that started late in the 1970s and has continued.
How much of that is related to the Pacific Decadal Oscillation and how much to global warming is the subject of debate, but if it is the former and the PDO reverts to the cold cycle, “as it was from the 1940s through the 1960s,” Ruggerone and Irvine aksed, “will natural‐origin salmon abundances decline more than they would without hatchery salmon? Answering these questions is beyond the scope of our paper, but they are important areas for future research.”