Pink salmon disrupt ocean ecosystem
Part II of II
Scientists who stepped back from looking at the trees to study the forest that is the vast expanse of the North Pacific Ocean have concluded that the explosion of pink salmon there, and especially hatchery-boosted pink salmon, is what has contributed to problems for other species of salmon, seabirds and more.
The study they published in the Marine Ecology Progress Series (MEPS) last week does not prove that hatchery fish have disrupted the entire North Pacific ecosystem, but it says all the available evidence points to this being the case.
Were the peer-reviewed document presented in a U.S. criminal court, it would likely fail to meet the burden of proof required to convict the fish Alaskans commonly call “humpies” of making life worse for more valuable and more desirable Chinook, sockeye and coho salmon along with a variety of seabirds and whales.
In a civil court, however, where the standard for deciding what is and what isn’t is a “preponderance of evidence,” it would be a different story. And it is in this sort of court that most science is judged.
Little of what we know as scientific truth can be proven beyond a shadow of a doubt. Newtonian physics? Yes. What goes up, always comes down. Even satellites shot into low earth orbit eventually return to the planet because of the irrefutable force of gravity.
Quantum physics? Well, let’s not even go there. It’s too damn complicated and theoretical. And the same for the world of medicine.
Few of the drugs we trust to stop and stall diseases today can be shown to work beyond a reasonable doubt. The best of them might work for all people most of the time, and some people all of the time, but almost none work for all people all of the time because individual people respond differently to different drugs.
The functions of the biological world are complex, and in the case of hatchery salmon, humans have made a complex situation even more so.
It is because of this that any discussion of too many salmon in the North Pacific has to start with hatchery fish because a large number of salmon in the ocean today, especially humpies, are not there naturally.
They are there thanks, or no thanks, to human environmental tampering that has pushed the biomass of North Pacific salmon to numbers never before seen in recorded history with “approximately 40 percent of the total adult and immature salmon biomass” compromised of pinks, according to the MEPS study.
Why it matters
All of those pinks have helped to initiate a cascade of problems that starts far down on the food pyramid where little fish are eating zooplankton before becoming big enough to eat other little fish.
‘We found compelling examples indicating that in odd years, predation by pink salmon can initiate pelagic trophic cascades by reducing herbivorous zooplankton abundance sufficiently that phytoplankton densities increase, with opposite patterns in even years,” the authors wrote.
The vacuuming up of North Pacific zooplankton by mobs of humpies has long been suggested as an explanation for why pink salmon runs are so much more abundant in odd-numbered years than in even-numbered years, the reason being that the odd-year fish consume so much zooplankton biomass that the next years fish, the even-year pinks, struggle to get enough to eat.
Not only is that the case, the scientists now contend, but the consequences of these every-other-year crashes in food supply ripple through the populations of salmon that spend years at sea.
“Widespread interspecific competition for common-pool prey resources can be dominated by pink salmon, as indicated by numerous biennial patterns in the diet, growth, survival, abundance, age-at-maturation, distribution, and/or phenology of ecologically, culturally, and economically important forage fishes, squid, Pacific salmon and steelhead trout, seabirds, humpback whales, and endangered southern resident killer whales,” they wrote.
The losers here are many, and salmon other than pinks take big hits. The MEPS study goes on to break things down by species.
“Among Pacific salmon species,” the study says, “sockeye salmon have the greatest diet overlap with pink salmon. Both species are primarily planktivores, but each can switch to higher trophic level prey such as small fishes and squid as they grow in their second season at sea.
“During a 10-year study in the central Bering Sea, the diet of sockeye salmon averaged 47 percent fish and squid, 44 percent zooplankton, and 9 percent other prey by weight. However, in odd years, when pink salmon were approximately 40 times more abundant,” the ratios changed and “the consumption of energy-rich fishes and squid declined 50 to 58 percent in sockeye salmon….
“These data suggest that pink salmon were able to consume fishes, squid, and energy-rich zooplankton more effectively than sockeye salmon when the availability of these key prey was limited.”
As a result, sockeye were forced to turn to less energy-rich foods, and their growth slowed, the result eventually being smaller, less valuable wild salmon when caught by commercial fishermen.
“Even bigger losses of squid in the diets of sockeye were taking place in the Gulf of Alaska but went unnoticed for decades,” the study adds. But that has now changed.
“A growing body of evidence indicates that pink salmon influence the growth, age, survival, and abundance of sockeye salmon throughout their range in North America,” the study says.
Sockeye, which are pound-for-pound three to four times as valuable as pinks, are the state’s money fish, according to the Alaska Department of Fish and Game. The study says they are declining in number and size because of pinks.
“The mean annual return of approximately 82 million hatchery pink salmon during 2005 to 2015 was estimated to reduce sockeye salmon productivity by 5 percent in the Bering Sea, 6 percent in the Gulf of Alaska, and 15 percent in British Columbia (Canada) and Southeast Alaska,” the study said.
The losses in the Bering Sea were more than offset by global warming, which increased productivity there. But the reverse has happened in Southeast Alaska and British Columbia.
“Sockeye salmon in British Columbia and Southeast Alaska have encountered unfavorable early and late marine conditions in recent decades, leading to declining survival and abundances,” the study said. “An analysis of up to 36 sockeye salmon populations from Puget Sound, Wash., through Southeast Alaska during the past 55 years revealed that high abundance of North Pacific Ocean pink salmon in the second year of sockeye salmon life at sea was associated with lower sockeye salmon productivity, reduced adult length-at-age, and delayed maturation.”
That study predicted that an increase from 200 million to 400 million pink salmon would lead to a 39 percent reduction in the productivity of Fraser River sockeye salmon.
The sockeye-filled Fraser River was once thought of as Canada’s Bristol Bay. But commercial fisheries there are now closed as Canadian salmon managers struggle to meet spawning goals.
Chinook are the salmon Alaskans call “king.” These are the biggest and most valuable of Pacific salmon and the state fish.
They have been in a general state of decline in size and number for decades.
Once they returned to the Kenai River south of Anchorage in such numbers and of such size that they attracted anglers from around the world. The world-record king salmon, a fish less than three pounds shy of 100 pounds, was caught in the Kenai in 1985.
For years after, many dreamed of becoming the first in the world to catch a salmon of 100 pounds. That never happened, and today the shine has gone off the Kenai where it is getting rare to see a king over 50 pounds, though such fish were common in the ’80s and ’90s.
The fading of the Kenai kings has never been fully explained, but the MEPS study points the finger at pinks again.
“Subadult Chinook salmon have been found extensively in offshore areas of the North Pacific Ocean and the Bering Sea, where they overlap with pink salmon,” the authors wrote. “Diet overlap between Chinook and pink salmon can be considerable, especially during the second season at sea for pink salmon, when they are large enough to consume squid and small fishes. The small energy-rich squid is a major component in the diet of Chinook salmon (and other salmon species) in the Gulf of Alaska, central North Pacific, and central Bering Sea.”
Chinook are even more dependent on squid than sockeye. Squid and small fish have been found to comprise 80 percent of the diet of Chinook in the Bering Sea when those prey are readily available as food.
But in odd years, when pinks are most abundant, squid are far less so. “Chinook salmon consumed 72 percent less squid and 44 percent less fish, but 44 percent more euphausiids compared with even years,” the study said.
Due to competition with pinks, kings appear to have gone from dining on steak and potatoes to surviving on bread and water. The results have manifested in the reduction in their number and the well-documented decline in their size.
“Average weight of commercially caught Chinook salmon was relatively stable over time when abundance of pink salmon was low during 1952 to 1975,” the study says. “Immediately after the 1977 ocean regime shift (to warmer water), body size of (average) Chinook salmon reached its maximum (20.5 pounds) and then declined steadily
over time as pink salmon abundance increased.
“Chinook salmon body size reached the long-term minimum during 2015 to 2021 (average 12.6 pounds) when pink salmon abundance was peaking and when marine heat waves became more frequent,” the study reported.
Alaska pinks are not wholly to blame here because Alaska’s success at farming the sea with pinks in the 1980s encouraged the Russians to jump into the hatchery business in a big way.
As a result, the Russians now sometimes see pink salmon returns so big as to swamp their processing capabilities. And American salmon sometimes pay the price for this Russian salmon production.
“…Moderate to strong support was found for an adverse effect of Russian pink salmon abundance on annual scale growth of Yukon, Kuskokwim, and Nushagak Chinook salmon during the third and fourth years at sea over a period of 30 years or longer,” the MEPS study reported. “Survival of two of the three major stocks of Chinook salmon in western Alaska declined with the running two-year abundance of Russian pink salmon during the third and fourth years at sea.”
Russian and U.S. hatcheries are combining to flood the Bering Sea and the Gulf of Alaska with pink salmon at the same time that warming is leading to major increases of naturally-spawning sockeye salmon out-migrating from Bristol Bay lakes while far from home Pacific Northwest king salmon appear to be moving ever farther north in search of better feeding grounds.
“Approximately 11 to 38 percent of Chinook salmon sampled for genetic stock identification in the southeastern Bearing Sea during 2005 to 2010 originated from the Pacific Northwest, raising concern that climate warming may be shifting salmon from the Pacific Northwest into a crowded Bering Sea where temperatures are cooler,” the study said.
“In support of this hypothesis, (Jack) Buckner (at the University of California Davis and colleagues from the National Marine Fisheries Service) in 2023 analyzed the growth of 48 stocks of Chinook salmon returning to hatcheries and spawning grounds in the Columbia River Basin, Oregon coast, and Washington coast (brood years 1976−2013), and found that growth of sub yearling and yearling far-north migrating Chinook salmon was negatively associated with pink salmon abundance.
“The effect of pink salmon on Chinook salmon growth was stronger than that of the tested oceanographic variables. Growth of sub-yearling Chinook salmon populations that did not migrate as far north was also negatively associated with pink salmon abundance, but to a lesser extent; growth of yearling Chinook salmon in the southern distribution area was not associated with pink salmon abundance,” but southern areas support far, far fewer pink salmon.
The Buckner study was one of more than 250 studies referenced by the authors who prepared the MEPS analysis. It would indicate that Pacific Northwest Chinook long struggling to survive in a region where hydroelectric dams, industrial-scale agriculture and urban sprawl have degraded their spawning habitat are now facing equal or bigger obstacles to survival sea.
One of Alaska’s most sought-after sportfish, coho are regularly described as “hard-fighting silvers” though they are equally tasty on the dinner plate. The farmed salmon industry in Chile built its business in part around raising coho and now produces them to the tune of about 450 million pounds per year.
In Alaska, however, most all coho are wild, and though they share less diet overlap with hatchery pinks than sockeye salmon, they appear to have been unable to fully escape the humpocalypse.
“…Diet overlap between (pinks and coho) increases during the second season at sea as pink salmon grow and begin to capture small fishes and squid,” the study says. “Consumption of squid by pink salmon becomes more pronounced during their final two or three months at sea, especially after they reach 2.2 pounds.
“Pinks at that time began competing with coho that” depend primarily upon energy-rich squid, the study says. “Over a period of 50 years (1970−2019), the average weight of coho salmon caught in the Southeast (Alaska) troll fishery declined with increasing biomass of pink salmon harvested in North America (an index of abundance) and increased with broad-scale, sea-surface temperature, as indexed by the Pacific Decadal Oscillation.
“The most likely mechanism responsible for those relationships involves predation by maturing pink salmon on squid, a key prey of maturing coho salmon. The biennial life cycles of pink salmon and squid contribute to distinct biennial abundances of maturing squid that are consumed by a single cohort of ocean age-1 coho and pink salmon.
“Thus, evidence indicates that predation by abundant odd-year pink salmon leads to fewer squid available to maturing coho salmon in odd years and to their reduced growth and body size.”
Chinook are the only salmon that have been shrinking more than cohos since the start of the new millennium, and this despite the fact that a warmer ocean should benefit coho.
“…In warmer ocean conditions, coho salmon are able to grow to a length greater than that in colder years,” National Oceanic and Atmospheric Administration (NOAA) scientists who have been studying coho returning to Juneau’s Auke Creek for decades reported in 2018. “This pattern has been reported elsewhere and attributed to the bottom-up increase of overall ocean productivity in years with warmer conditions.”
They also warned at that time that the increased productivity of the ocean for coho was being undermined by the humpy boom.
“The negative relationship between coho salmon length and pink salmon harvest (numbers) suggests negative impacts of competition for food resources at high pink salmon harvest,” they wrote.
The Alaska Board of Fisheries the same year allowed yet another increase in hatchery humpies.
After deciding there was no definitive proof hatchery fish do any harm to wild fish, the Board voted 4 to 3 to allow the private Valdez Fisheries Development Association to add another 20 million pink salmon eggs per year to a hatchery operation already producing more than 15 million pinks per year.
The Alaska Department of Fish and Game reported hatchery production of pinks in Valdez this year exceeded the number of wild pinks produced in all of Prince William Sound.
With the calculated return of Sound pinks near 65 million, the state agency reported an early estimate of “20.32 million wild stock fish, 20.38 million VFDA fish, and 24.20 million Prince William Sound Aquaculture Corporation hatchery fish.”
It is now stuffed with the by-Alaska-standards little salmon. VFDA was reporting the average size this year at two and a half pounds.
Chum salmon – widely known in Alaska as “dog salmon” for their use as sled-dog food along the Yukon River in the state’s Interior in days gone by and now generally marketed as “keta” because “dog salmon” doesn’t hold much appeal to modern consumers – were once thought to be largely immune to competitive pressures for food in the ocean.
As the MEPS study notes, “their unusually large stomach is uniquely adapted to process
large quantities of low-calorie gelatinous plankton, which is thought to be an evolutionary response to reduce competition with other salmon species, especially highly abundant pink salmon.”
But that does not appear to be enough to fully protect them from the wave of humpies.
“Despite this adaptation, there is evidence for competition between chum and pink salmon,” the study says. “For example, in odd years when maturing pink salmon are
highly abundant in the Bering Sea during June and July, zooplankton abundance has been” shown to decline.
As a consequence, the study says, “chum salmon consumed 40 percent more low-calorie gelatinous zooplankton and 30 percent more pteropods, and 40 percent less high-calorie prey than in even years when few pink salmon were present (from) 1991 to 2007.”
The lower-quality diet resulted in smaller fish and less healthy fish packing less of the fat salmon rely upon to make their way long distances upon the streams of their origin to reach spawning grounds.
The study went on to cite examples of pink salmon influences on the number and size of chum salmon from the Bering Sea east and then south around the rim of the Gulf of Alaska all the way to Oregon.
“In the Salish Sea (off southern British Columbia, Canada and Washington state), where maturing pink salmon are approximately 40 times more abundant in odd versus even years,” the study said, “chum salmon exhibited strong biennial variations in abundance, size, age-at-maturity, and productivity consistent with the hypothesis of competition for food with pink salmon
“Overall, chum salmon returns were 32 percent lower in high pink salmon years (odd) compared to low pink salmon years (even) during the last five decades.”
Pinks in the Salish Sea are primarily wild fish. The combined releases of hatchery pinks by British Columbia, Canada, and Washington state represent about 2 percent of the number of young pinks released in Alaska each year, according to the University of Alaska Institute of Social and Economic Research.
Farming the sea
British Columbia and Washington differ from Alaska in that neither is involved in farming the sea as a business. Their hatcheries raise relatively small numbers of salmon to boost salmon runs damaged by development or to provide fishing opportunties for sport fishermen.
Alaska is engaged in industrail agriculture or ocean “ranching” as Alaska hatchery operators prefer to call their farming. It decades ago became a big business in the 49th state and is today governed by the number one rule for all profitable big businesses: efficiency.
“Pink salmon are economically efficient,” as the website Salmon Hatcheries for Alaska clearly states. “They have a year-long life cycle and are the primary salmon export from the state of Alaska. They result in a $92 million annual economic output, according to ADF&G. Hatcheries primarily produce pink and chum salmon because both are released into salt water soon after hatching, which is more economical than rearing species that require being released in freshwater.”
What the hatchery-promotion website doesn’t say is that these hatchery fish are also the lowest-value salmon, pound for pound, in Alaska and appear to be suppressing the production of other larger, more valuable species.
“Hatchery production in Alaska is designed to supplement – not replace – wild stock production,” the website admits, even though it appears the hatcheries are now in the business of replacing wild fish.
In Southeast Alaska, there looks to have been a trade of wild chum for hatchery chum, but in much of the rest of the state, the MEPS study points to a trade of wild kings, sockeye and coho for hatchery pinks.
Whether this is what income-tax-paying Alaskans wanted in the 1970s when they voted to approve millions of dollars in bonds to build state hatcheries later turned over to private, nonprofit corporations controlled by commercial fishermen is unclear.
But what is clear is that the hatchery promises made around that time were not kept as hatchery operators quickly turned their attention from the fish Alaskans wanted produced to the fish that could most easily and cheaply be produced for commercial profit.
As the hatcheries were coming online in the 1980s, the state promised that “the long-term plan for salmon in Alaska calls for nearly 143 million fish for harvest annually, of which 51 million are to be produced by enhancement and rehabilitation techniques. Included within this harvest of 51 million are 25 million chum, 8 million sockeye, 1.5 million coho, and 300,000 Chinook salmon; the remainder will be made up of pink salmon.”
The goal of 51 million hatchery fish has been vastly exceeded. In 2013, state hatcheries were credited with producing a record catch of “111.5 million hatchery propagated salmon” of which 82.4 percent were pinks with 76 million of them returning to the Sound alone.
The combined total of pinks and chums comprised 96.2 percent of hatchery production that year, but the coho return was also a record at 1.7 million. It marked the first and last time in the years since ’83 that the promise of 1.5 million coho per year was reached.
The goals have never been met for Chinook, sockeye or chum.
The hatchery returns of those fish last year totaled 86,000 kings, or 29 percent of the promised goal; 1.5 million sockeye, or 19 percent of the promised goal; 844,000 coho, or 56 percent of the promised goal; and 12.3 million chums, 49 percent of the goal, according to state numbers.
And yet, despite 2022 being an even-numbered year in which pink salmon returns are historically half or less those of odd-numbered years, 28.6 million hatchery pinks came back to Alaska – nearly twice the 16 million per year originally promised.
And the pink return this year is on track to be somewhere near twice that of last year. Meanwhile, the state’s preliminary commercial harvest report is showing a statewide catch of 190,000 Chinook.
In the 1970s – before Alaska charged full force into the hatchery business – the catch of kings averaged 619,000 per year from a colder, less productive ocean. The hatcheries were supposed to add another 300,000 salmon to that total. Instead they appear to have helped reduce the catch of Alaska’s most prized salmon by more than two-thirds.