A schematic of how salmon in Alaska influence shearwaters in Australia. The dark lines are shearwater migration routes. The yellow circles the range of pink salmon from Japan and Russia, the red the range of Alaska salmon/National Academy of Sciences
With a growing number of Alaskans pushing the state Board of Fisheries to take a closer look at 49th state salmon ranching, scientists from the University of Alaska Fairbanks and Australia have joined other scientists warning of the ecosystem consequences of hatcheries dumping billions of hungry young fish in the North Pacific each year.
Alan Springer and his colleagues contend seabirds are starving in unusually large numbers because the salmon, especially pinks, consume too much of the food that would normally support the birds.
What they discovered, as reported in a peer-reviewed study published online Monday at the website of the Proceedings of the National Academy of Sciences of the United States of America on Monday, is “another example in a growing list of ecosystem disservices of an abundant species of North Pacific salmon and the need to include ecosystem processes at such geographic scales in conservation and management considerations for this northern open ocean.”
“Pink salmon in the North Pacific Ocean have flourished since the 1970s with growth in wild populations augmented by rising hatchery production,” they wrote. “As their abundance has grown, so too has evidence that they are having important effects on other species and on ocean ecosystems.”
“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 wrote.
Springer and nine co-authors, most of them Australians, now contend the ecological implications of stuffing the ocean with pinks reach far beyond Alaska.
They paint a picture of consequences from a Prince William Sound salmon spill that could over the long term dwarf the damage of the infamous Exxon Valdez oil spill of 1989. Approximately 250,000 seabirds perished in the oil spill, scientists eventually concluded.
Annual kills
The bird biologists have fingered pink salmon as the villains in the death of what could be tens of thousands of short-tailed shearwaters per year for decades, a problem that could only get worse as hatchery production continues to increase.
“….Beginning in 2007 and coinciding with the increasing abundance of odd-year pink salmon, wrecks occurred in every odd year to at least 2013,” they wrote. “Wrecks” are the descriptive term for massive die-offs of shearwaters. The phenomenon has been regularly observed since the 1800s, but has accelerated in recent years.
“The wreck in 2013 was extreme, when very high numbers of birds were stranded in Australia and Tasmania, and even in New Zealand, where they do not nest , and corresponded with extremely high abundances of pink salmon returning to United States waters,” they wrote.
“Birds in those wrecks…were emaciated, suggesting that they failed to accumulate sufficient fat before departure on their southward migration to sustain them until they could refuel upon their return.”
Short-tailed shearwaters summer in the North Pacific Ocean and the Bering Sea where they compete with young salmon for food.
“Diets of pink salmon and short-tailed shearwaters overlap, and the biennial pattern in shearwater body condition has been linked to competition with pink salmon for common prey,” the scientists wrote.
They noted the overall abundance of pinks sharing shearwater habitat stayed within a “comparatively small, low range from the early 1950s to the mid-1970s, then increased markedly through about 1990.”
Alaska hatcheries went from producing about 20,000 salmon per year in 1975 to producing 27 to 54 million salmon per year by the 1990s, according a 2007 review of “Alaska’s salmon hatchery ocean ranching program.”
Alaska banned salmon farming in 1990 in the hopes of limiting competition for salmon in the market place, but it went all in on private, nonprofit hatcheries owned by commercial fishermen and financed with state loans.
The big pink increase in the 1990s “was followed by a second period of relative stability to about 2004,” according to Springer and his colleagues. “Beginning in 2005, odd-year stocks increased substantially, whereas even-year stocks remained about the same as in the previous interval. The odd-year mean in 2005–2015 increased by 35 percent over the odd-year mean for 1990–2004.”
Pink salmon spend only a year at sea but have such an impact on the marine ecosystem that it is believed one generation of pinks can suppress the next generation.
“Possible mechanisms are cannibalism, disease transmission, food depletion and habitat degradation by which one lineage affects the other, although no mechanism has been well-studied,” Martin Krkošek and colleagues reported in Proceedings of the Royal Society Biological Sciences in 2010.
Springer and colleagues note the peak years for pink salmon abundance correlate with the big shearwater wrecks, and the shearwater die offs have been getting worse as hatchery production has boomed in the new millennium.
Global implications
Springer and colleagues argue all the hatchery fish being pumped out by Japanese hatcheries dating back to the 1970s and the newer hatcheries in Russian and Alaska are having global implications:
A pink salmon fry released in Prince William Sound rides the Alaska coastal current west to the Bering Sea to eat the food that would normally nourish a shearwater that leaves for its wintering and breeding grounds in Australia only to die of starvation.
The scientists describe this as a macrosystem in which pink salmon alter ecological interactions at the “local, regional, basin, hemispheric, and transhemispheric” levels.
“The desire to continue to raise production levels of wild and hatchery salmon is understandable,” they concede. “The overall annual multinational economic value of Pacific salmon is in the order of $1 billion US, and the industry employs tens of thousands of people. But it is now time to take stock of the consequences—the ecosystem
disservices of salmon—of doing so on other economic, social, cultural, and ecological values in the North Pacific/Bering Sea and, because of the teleconnection described here, in the South Pacific/Tasman Sea as well.”
Whether anyone cares about the ecosystems consequences of this sort of environmental tampering only time will tell. The short-tailed shearwater is a brown, nondescript, gull-like bird common to the Pacific Ocean.
Even the scientists admit, “the short-tailed shearwater is not a species in peril.
“But,” they add, “the apparent response of these birds, as well as responses of humans, resident North Pacific/Bering Sea seabirds, other salmon, herring, and likely species yet to be identified, to ecological forcing by pink salmon suggests that pink salmon are altering the distribution of wealth stored in this macrosystem. Together, these responses emphasize that we must develop a deeper conservation conscientiousness for this entire oceanic system and more informed approaches for the management of the whole.”
That altruistic view runs up against powerful economic influences and, at least in Alaska, a lot of skepticism. Even some Alaska commercial salmon fishermen dependent on salmon species that might be losing out to hatchery pinks appear reluctant to accept the idea that the salmon produced by other Alaska fishermen could be altering the environment.
Dumping more and more hatchery salmon into the ocean has always been viewed as a good thing in Alaska, so how could it possibly be bad?