Concern grows among fishermen and scientists about low silver salmon returns in Cook Inlet

Feisty at the end of the rod and light and mellow at the center of the plate, silver or coho salmon have always been a symbol of the end of summer in Alaska. But, in the last several years, as tourism has wound down and the leaves have started to change around Cook Inlet, the silvers have failed to show up in the numbers people are used to. Fishermen and scientists are starting to worry.

“One year’s poor return doesn’t tend to really send up red flags, but year after year after year, then you start to get concerned as a manager,” said Matt Miller, Alaska Department of Fish and Game fisheries management coordinator for Cook Inlet.

This has not been a great fishing year overall. Commercial harvests for all five species of Alaska salmon statewide were down, according to the McKinley Research Group, which called the across-the-board poor harvest “atypical.” The Cook Inlet region saw the largest coho decline, at 84% below the harvest the year before, which was also poor. The inlet also saw a similarly significant decline in pink salmon harvest, the research group reported.

Last year, according to Fish and Game salmon landings data, the commercial harvest of coho in Cook Inlet was the smallest — just over 80,000 fish — since the department started keeping track in 1985, a highly abundant year when fishermen brought in 670,000 fish.

Fish and Game issued sport and commercial closures for coho fishing beginning in late summer across the entire Susitna River drainage, northern Cook Inlet and Anchorage. There were also restrictions placed on Kenai Peninsula rivers and streams including the Kenai, Kasilof and the lower Cook Inlet systems. Just last week, on the Kenai River, managers removed the option of sport fishing with bait and reduced the bag limit to one coho.

At The Bait Shack, which serves people fishing in Ship Creek in downtown Anchorage, owner Dustin Slinker has been keeping a careful eye on fish runs for a decade. Slinker hosts a silver salmon derby — the “Coho Rodeo” — that he decided to cancel this year, after postponing it, due to extremely low numbers, “erring on the side of fish conservation,” he said. The creek was closed to coho and chinook fishing for big pieces of the summer and that’s reflected in his business spreadsheets. Over the time he’s owned his business, he’s seen king salmon runs decline and then, for the last several years, he says the silver runs have been paltry.

“When you watch these fish decline — it makes you appreciate the fish — especially for lifelong Alaskans, maybe multigenerational families that grew up with the abundance of big king salmon, or seeing the pictures of big kings, it used to be a way of life,” he said. “It’s hard to see that going away, it seems like we are just continuing down the same path.”

The William Jack Hernandez Sport Fish Hatchery at Ship Creek, which is operated by Fish and Game, is the only hatchery in Cook Inlet producing coho salmon. Average returns to the mouth of the creek are an estimated 7,000 fish, of which an average of 4,500 are caught by sport fishermen and 2,500 make their way back up the creek. Some of those stay in the creek, and others enter brood holding raceways at the hatchery, said Chuck Pratt, sport fish hatchery program supervisor. The hatchery needs about 350 breeding pairs to stock the creek as well as to stock sport fishing spots, called “terminal fishery locations,” at Campbell Creek, Bird Creek, Eklutna and the Homer spit, he said. This year the hatchery may not get enough fish to do the offsite stocking, he said.

“We have low years, but this is by far the lowest escapement that the program has had,” he said.

Earlier this month, the hatchery had about 154 females and over 200 males in the holding raceway.

“Coho move based on rain and atmospheric conditions,” he said. “Over the past week, we’ve had 86 fish move up, which raises our spirits.”

Monte Roberts, head of the Kenai River Professional Guide Association, said he’s been taking clients out to fish on the river this season, but they’re finding a lot of trout and few silvers. This has been going on since 2021, he said, and guides are concerned. They are particularly worried about a few years of big rains and high water events and wonder about the impact of those on spawning fish. They’d like Fish and Game to do more to get a handle on the number of silvers in the river and what might impact them, he said.

“We’ve known that silvers have been kind of in trouble for a few years, the department didn’t think they had a problem, but maybe they do,” he said.

Fish managers have limited tools when fish runs start to falter, Miller said. They can work to reduce harvest and try to ensure salmon have good spawning and rearing habitat, he said. In terms of scale, silver salmon runs are smaller and less of a target for commercial fishermen than red or king salmon. Because of this, they have been subject to less scientific study than other species. There are scores of small coho runs spread across the inlet, but Fish and Game counts the fish returns in only a handful of places and some of those weirs have been overwhelmed in recent years by high water, making it hard for managers to get a definitive picture of their abundance.

“What I tell people is be patient, especially with coho,” Miller said. “We don’t have a lot of information and we are doing what we can with the information that we have.”

Spawning female coho lay eggs at the heads of rivers in the fall, where they are fertilized by male salmon. The eggs hatch the next spring once river ice melts, and the fish enter the river where they grow for two to three years before heading to sea for about a year. Some fishermen have worried that coho may be being caught in large numbers by trawlers catching bottom fish with large nets in the open ocean, but according to the North Pacific Fisheries Management Council, coho salmon make up a very small proportion of the salmon caught incidentally as bycatch.

[Two Kodiak trawlers unintentionally caught 2,000 king salmon. Now a whole fishery is closed.]

Page Herring, who is on the board of the Northern District Setnetters, has been commercial fishing in Cook Inlet for 45 years. She said invasive northern pike also have a big impact on cohos. Over time, the coho runs have become more erratic, she said.

“The coho are like the caribou of the marine population,” she said. “Sometimes you see ‘em, sometimes you don’t. They’re magic.”

Scientists are still studying what might be causing the decline, but in-river water temperature anomalies and changes in ocean conditions linked to climate change — which have been connected to declines in other salmon species in Alaska — are two hypotheses. Along the West Coast, some coho salmon runs have declined to the point that they have been listed as endangered. Factors that have caused declines there include dams and other habitat issues, overfishing, interactions with hatchery fish, large precipitation events that flood rivers and changes in oceans, both of which are linked to a changing climate.

There’s an Alaska study underway — a partnership between the U.S. Fish and Wildlife Service, University of Alaska Anchorage and Cook Inletkeeper — in the Deshka River system that looks at water temperature impacts on chinook and coho salmon. In general, water warmer than 70 degrees has shown to be deadly for salmon. The Mat-Su region has some of the warmest stream temperatures in Alaska.

“Water temperature affects all phases of the salmon life cycle; egg/embryo survival, juvenile growth, timing of seaward migration and migration rate of returning adults. Warm water temperature induces stress in salmon and makes them more vulnerable to pollution, predation and disease,” the study says.

To sleuth the causes of failures in fish runs, scientists often look back in time. Salmon runs tend to be a little bit like time capsules that give indicators about the conditions they faced in rivers and the sea. In another study, scientists have found that heavy rains and hot, dry weather blocked fish migration and had negative effects on juvenile king salmon growth around Cook Inlet. It’s possible that the record hot dry summer of 2019 — which caused in-river salmon die-offs across the state — was hard on coho salmon, too. The low returns could be related, said Jon Gerken, fish biologist at the Anchorage Fish and Wildlife Conservation Office. Water temperatures in the Deshka system, for example, were above the temperature the EPA designates for rearing. Scientists made the assumption that some fish died.

“We could have had massive mortality all over the place in all these systems,” he said.

It’s possible for abnormally high water temperatures in 2019 to have reverberations for several cohorts of salmon, he said, beginning with the eggs laid in 2018 that hatched in the spring of 2019, which would have been returning in 2022 and 2023. The fish born from the eggs laid in the fall of 2019, hatched in 2020, spent two to three years in freshwater and then went to sea, would have been the ones expected to return in 2023 or 2024, Gerken said. All those runs have been low. What happens next? Scientists have to wait and see, he said, but if fewer salmon spawn, generally speaking, there are fewer offspring.

Freshwater is a big factor for silvers, because they spend much of their lives there, Gerken said. But he cautioned there are other things that play a role in the ocean that may include food sources, ocean acidification and predators.

Miller, with Fish and Game, agreed. He said that silvers feed on forage fish in the ocean like sand lance and herring.

“They largely feed on the same food sources juvenile king salmon feed on and we know that ocean conditions have not been favorable to king salmon,” he said.

The year 2019 was both very warm and very dry, said Rick Thoman, Alaska climate specialist with the Alaska Center for Climate Assessment and Policy at the University of Alaska Fairbanks. In Anchorage and Talkeetna that year, low rainfall totals were very anomalous, the type that occurs less often than once in 500 years, he wrote in an email.

“But certainly very warm and very dry (though perhaps not quite as dry as 2019) summers are likely to occur again,” he wrote.

Coho have had other periods of low returns, Miller said, including one in the 1990s that raised alarms. The Board of Fisheries and department took a similar approach then, implementing restrictions on commercial and sport fisheries.

“Then a few years later, they just started coming back,” he said.

The limits on fishing did get more fish to the spawning bed, he said, but changes outside of managers’ control that improved their survival in the ocean likely had more of an impact.