A significant drop in Pacific Ocean salmon harvests last year is driving new questions as to whether the ocean has reached its salmon carrying capacity.
The discussion comes at a time when sockeye returns to Alaska’s nationally recognized Copper River are again struggling.
The North Pacific Anadromous Fish Commission (NPAFC) – an intergovernmental working group supported by Canada, Japan, the Republic of Korea, the Russian Federation and the U.S. – at the end of May reported that 2020 commercial salmon harvests hit a low not seen in almost four decades.
Though the global pandemic might have had some effect on the unusually low catch, the harvest is still believed to be a reflection of a major drop in salmon numbers.
“Pacific salmon abundance in the North Pacific during 2020 was the lowest recorded (606.7 thousand metric tonnes, 322.5 million fish) since 1982, as indexed by aggregate commercial catches” was how the Commission put it.
Respected Canadian fisheries scientist Dick Beamish, one of the world’s top authorities on Pacific salmon, went farther in an email.
“There is no doubt that declining trends in the commercial catch result from decreasing coastal ocean carrying capacity,” he wrote. He also attached a copy of a presentation he was invited to deliver to the Canadian Federal Committee on Fisheries.
“There is a principle in ecology that the abundance of plants and animals that produce large numbers of seeds or babies is determined by the available habitat and not by the number of seeds or babies,” he observed there. “Salmon produce a large number of babies and the available habitat is mostly the ocean. There now is solid, published evidence that once in the ocean the abundance of salmon is mostly determined in the first months.”
Salmon are a species ruled by death. University of Washington scientists studying pink salmon found that more than 87 percent of eggs died before becoming fry. Of the eggs that hatched, 65 percent of the fry died within 40 days, and 85 percent of the survivors died before becoming adults able to return and spawn.
In-river factors affecting the survival of these fish have been well studied, but the ocean remains a great, blue hole. Though some question how the vast expanse of the Pacific could lack for salmon pasture, ocean studies are showing that the world beneath the surface of the water is much like the world on land:
There are good habitats; there are bad habitats; and there are a lot of variations in between.
Ocean-wide pink salmon appear to be doing generally well, despite harvest declines in Russia in 2020, but longer-lived species of salmon are notably struggling, possibly due to food shortages. Pinks are the smallest, shortest-lived and fastest growing of the six species of salmon.
Despite their relatively small size, the NPAFC reported that in 2020 “pink salmon constituted the majority of the total commercial catch (46 percent by weight) followed by chum (27 percent) and sockeye salmon (23 percent). Coho comprised 3 percent of the catch, while Chinook salmon, cherry salmon, and steelhead trout were each less than 1 percent of the catch by weight.”
Pink catches in Alaska have in modern times been boosted significantly by production from private, non-profit hatcheries controlled by commercial fishermen. Questions have been raised as to whether larger, longer-lived salmon are paying the price for the artificial propagation of the fish Alaskans often call “humpies” due to the humped backs that male pinks develop as they move onto the spawning grounds.
Scientists looking for lasting damage from the 1989 Exxon Valdez oil spill in Prince William Sound (PWS) in 2017 stumbled on indications that large returns of pinks to hatcheries in the Sound were linked to significant declines in returns of sockeye salmon in the Copper River just south of the Sound.
“All sockeye salmon stocks examined exhibited a downward trend in productivity with increasing PWS hatchery pink salmon returns,” the state and federal scientists wrote in a peer-reviewed study published at PLOS-One. “While there was considerable variation in sockeye salmon productivity across the low- and mid-range of hatchery returns (0–30 million), productivity was particularly impacted at higher levels of hatchery returns.
“Pink salmon have been found to negatively affect sockeye salmon productivity and growth from British Columbia and Southeast Alaska, Bristol Bay, Kodiak, and Russia. Pink and sockeye salmon compete in the marine environment due to a high degree of similarity in diets, including similarities in diets of adult pink salmon and juvenile sockeye salmon.”
The study – which included scientists from the Alaska Department of Fish and Game – has been largely dismissed by Bill Templin, the agency’s director of commercial fisheries research, who rightly argues that correlation is not causation.
The scientists who published in PLOS admitted they could not specifically say how hatchery production served to depress wild production.
“We do not know if possible deleterious interactions between hatchery pink salmon and wild sockeye salmon in this study are from predation or competition, or whether they occur in nearshore or offshore areas,” the study said. “Pink salmon feeding may cause a general depletion of prey availability that could impact sockeye salmon without tight spatial overlap of these two species. In this regard, the apparent impact to sockeye productivity may reflect a general increase in pink salmon abundance across the northeast Pacific rather than increased abundance of hatchery pink salmon to PWS (Prince William Sound) in particular.”
The predicted return of prized sockeye to the Copper was put at 1.3 million when Fish and Game issued its forecast in January. That was more than 37 percent below the 10-year-average harvest, and the depressed forecast is turning out to have been optimistic.
Because of a shortage of sockeye, commercial fishermen based in the small, Gulf of Alaska port of Cordova have been allowed to fish for only five days since the May 17 start of the season. A normal season sees them fishing at least twice a week.
Commercial closures have allowed fishery managers to reach the spawning escapement goal of about 300,000 sockeye through the commercial nets and in-river by this date, but the protection of the spawning stock has reduced the season’s catch to fewer than 91,000 fish as of Wednesday.
The commercial fishery was open again on Monday with the catch expected to grow by another 30,000 or so, but the run is now past its peak. Half of the return has usually arrived by mid-June. At the rate things are going now, commercial fishermen will be lucky to net a harvest of 200,000 of the fish Alaskans commonly call “red salmon” because of the color they turn on the spawning grounds.
The situation on the Copper appears to reflect a Gulf of Alsaka wide decline in sockeye.
While the fish have been thriving in Bristol Bay due to global warming, they have been struggling around the Gulf Coast from the Alaska Peninsula east to Cook Inlet and south to the Fraser River in Canada.
A watershed famous for its once huge runs of sockeye, the Fraser saw one of its worst returns ever last year.
The Fraser fish do not start arriving until late June, and the performance of sockeye runs to the north will give the Canadians no reason for optimism this year.
And sockeye catches in a so-called “cost recovery” fishery conducted in Resurrection Bay near Seward by the Cook Inlet Aquaculture Association (CIAA) are also lagging.
Through June 9, the CIAA has harvested but 16,000 of the 189,000 sockeye it is permitted to catch to cover hatchery operating costs, according to Fish and Game, which reported that for “the last 10 years approximately 62 percent of the final cost recovery harvest had been landed by this date on average.”
Those numbers would put the sockeye return to the Bay 75 miles south of Alaska’s largest city more than 100,000 fish behind the curve.
Closer to Anchorage, the state had as of June 13 counted 169 sockeye through the weir on the Russian River, one of the state’s most popular streams for anglers. There were more than 1,200 on the same date last year. The five-year average is more than 7,000, but that is inflated by a record early return in 2010.
A weak early return is usually a harbinger of a weak run, but not always. The June 13 count in 2006 was but 247 and the run topped 80,500 – about double the top of the escapement goal for spawners.
That said, in most cases when the count was below 500 by June 13, the total run ended up in the lower end of the biological escapement goal of 22,000 to 42,000 sockeye.
Salmon exist in a world where death is a constant. U.S Geological Survey scientists studying chum salmon in the Kwethluk River in Western Alaska in 2007 and 2008 calculated that only about 5 percent of the salmon spawned in that river survived to make it to sea.
Many eggs failed to hatch. Many alevins never got out of the gravel alive. Many fry died before going to sea.
This is normal. Other North American studies have found egg-to-smolt survival rates from a low of 1.5 percent to a high of 14.2 percent,
The odds were once thought to improve for the salmon that made it to sea. but marine survival is coming under increased scrutiny, Canadian David Welch and his colleagues at Kintama Research Services in Nanaimo, British Columbia, have documented a long-term, 65 percent decline in Chinook (king) salmon tied to falling marine survival along the North American coast.
“The abundance of salmon in the North Pacific has reached record levels,” they wrote in their peer-reviewed study published in Fish and Fisheries last fall. “However, most of the increase is in the two lowest valued species, (pinks and chums) in far northern regions, at least in part due to ocean ranching.
“In contrast, essentially all west coast North American Chinook populations including Alaska are now performing poorly with dramatically reduced productivity.”
Their study noted that other fishery scientists have since the 1990s been calling for more and better research to sort out the factors driving salmon survival at sea, but marine issues were overwhelmed by concerns about dams and development on land.
“The historical pattern of declines in salmon abundance (steeper in the south, less so in the north) were originally assumed to reflect a freshwater anthropogenic (human) cause because of the greater degree of freshwater habitat modification in the more populous southern regions,” they wrote.
Declines in Chinook, along with Gulf Alaska sockeye and coho (silver) stocks have raised some questions as to whether habitat modifications are the only factors causing low abundance of salmon in the Columbia and other Pacific Northwest and Canadian rivers.
“The recent recognition of the decline in Chinook returns across essentially all of Alaska and the Canadian portion of the Yukon River, where anthropogenic freshwater habitat impacts are negligible, is another example of how simple explanations are potentially flawed,” Welch and his colleagues observed. “If survival across this vast swathe of relatively pristine territory is severe enough to seriously impact salmon productivity, then there is littlehope that modifying freshwater habitat in more southern regions will support a newly productive environment for salmon.”
The latest NPAFC raised questions as to whether marine survival problems have now spread beyond Chinook.
“The total North American catch in 2020 was 252.7 thousand metric tonnes, which was the lowest since
1977,” the report said. . Chum salmon catch has declined from 101.2 thousand metric tonnes in 2017 to 30.6 thousand metric tonnes in 2020.”
Despite another banner year for sockeye salmon in Alaska’s Bristol Bay, the report noted the “sockeye salmon catch declined in 2020 to 107.4 thousand metric tonnes, compared to the five-year average of 133.6 thousand metric tonnes….The 2020 chum salmon catch in Alaska was the lowest since 1989.”
“Particularly low catches of chum and sockeye salmon in 2020 resulted in the lowest total catches of salmon on record (4.5 thousand metric tonnes) in the NPAFC database for Washington, Oregon, and California combined,” the report noted.