The massive, free-range, salmon-farming operation run by commercial fishermen in Alaska’s Prince William Sound appears to be undermining the natural spawning success of pink salmon there, according to a peer-reviewed study published in the journal “Evolutionary Applications” earlier this month.
The study reported finding “some of the smallest relative reproductive-success values ever observed in Pacific salmon” in streams filled with a mix of wild fish and hatchery strays.
Other than illustrating another sign of humankind’s massive footprint on the planet, however, the significance of this change driven by the multitude of pinks straying from the region’s industrial-size hatcheries is unclear.
Wild pink salmon stocks in the Sound remain in excellent shape with the Alaska Department of Fish and Game this year reporting the wild “pink salmon run was above average in 2021, encouraging given that wild fish were from the parent year in
2019 when spawners returned to dewatered streams amid a record-setting drought.”
The Evolutionary Applications study of hatchery fish led by state fisheries biologist Kyle Shedd with help from colleagues at Fish and Game and the Prince William Sound Science Center might also have shed some light on how those returns came back strong despite the drought faced by their parents in the spawning year of 2019.
The freshwater in the Sound’s short, steep salmon stream – or at least that in the two streams that have been the subject of intensive genetics studies – does not appear to be as productive as the brackish water where the streams meet the ever ebbing and flooding tides of the sea.
“Parents sampled upstream had 59 percent as many offspring on average as pink salmon sampled in the intertidal” area, the study reported. If those results were to hold for all streams in the Sound, low water pushing more pinks to spawn intertidally might actually increase rather than reduce production although there is clearly a limit as to how much of a drought the fish can survive.
Saltwater will kill eggs in the gravel, so they need some flow of freshwater even if it is the little flowing beneath apparently dewatered streams. Old studies in Southeast Alaska, meanwhile, showed an interesting push-pull between environmental conditions for intertidal spawning pinks.
Warmer ocean waters, especially during cold winters, improved the survival of eggs and alevins in the gravel of intertidal areas, but eggs that didn’t get enough water to reduce the salinity of the ocean died. If the parent fish spawned too far outside the zone of brackish water, their young were doomed.
The survival problem scientists documented in the Sound by genetically fingerprinting adult fish and then looking for their fingerprints in the genes of returning young are not, however, due to environmental problems related to habit, but to human-driven problems, albeit accidental, related to salmon wandering into Sound streams to spawn instead of returning to the region’s hatcheries.
Alaska has a massive fish-farming program, but it does not confine the fish to pens as in Norway, Chile, Scotland and elsewhere.
Instead, the fish are born in hatcheries, raised there briefly, and then released to free-range the ocean. Net-pen farming was banned in Alaska three decades ago, and the state prefers to call what it does “ranching” rather than farming.
The returning fish are sold as “wild-caught,” which subtly distinguishes them from wild fish without overtly alerting consumers to their origin. Alaska, for a time, led international efforts to market the idea that farmed salmon were inherently unhealthier than those caught in the ocean but has now backed away from that idea.
- “Superior flavor and texture…prized around the world”
- Made in America origin
- And the chance for consumers to help support “generations of fishing families and communities”
Much of the shift in strategy appears tied to the fact that the major fish processors that help fund the Institute are these days deeply involved in sales of net-pen farmed salmon, which dominate the global market.
Approximately 75 percent of the salmon eaten around the world today is farmed (not counting U.S., Japanese and Russian hatchery returns) and the percentage is growing. The net-pen farmers have enjoyed record profits as sales of fresh salmon have skyrocketed during the pandemic.
Alaska, unfortunately, has limited access to fresh-salmon markets because of the seasonability of its salmon returns. As a result, many of the hatchery-returning fish still go into cans for which increasing market demand is projected, but primarily in lower-value markets.
“Owing to rise in consumers’ purchasing power, (the canned-salmon) market is likely to increase significantly in developing countries. Furthermore, the vast customer base in developing nations is likely to have a significant impact on segment growth,” according to Allied Market Research.
And where there are higher-valued markets for canned salmon – such as those for boneless, skinless filets – the farmers are increasingly getting into the market. Still, Alaska canned salmon, now sometimes also packed in pouches, overwhelms the list of the “The 8 Best Canned Salmon in 2022” posted by The Spruce Eats, a website for foodies.
Unfortunately, the website’s suggestions on the best-canned salmon also come with the proviso “if fresh salmon isn’t available….”
Competition from the net-pen farmers for fresh fish makes the fishing business in Alaska a battle for companies trying to take advantage of the tens of millions of pink salmon that now return each year thanks to the annual ocean stocking of more than 700 million pink salmon.
The 49th state is a world leader in ocean ranching with a total release of “approximately 1.8 billion juvenile salmon annually,” according to the study. This is largely thanks to a government-funded hatchery program begun by the Fish and Game in the 1970s.
The hatchery salmon that aren’t pinks are almost all higher-value chum salmon once commonly referred to as “dog salmon” in the 49th state because of the hooked snouts and obvious, canine-like teeth that develop on males during spawning, but now most often marketed as “keta salmon.”
Humpies gone wild
Humpies – as Alaskans usually call pink salmon, the males of which develop huge humps on their backs as they begin the reproductive stage of life – are by far the most abundant salmon in the state.
And though they might all look alike in Sound streams, according to the new study, they don’t all perform alike.
“Reproductive success, measured as sampled adult offspring that returned to their natal stream, was significantly lower for hatchery- versus natural-origin parents,” the study found, with female humpies performing far worse than males.
Hatchery females that decided to spawn in the wild were less than a half as productive as their wild sisters with the range of success falling from 0.47 all the way down to 0.03. Some males did much better, with the range running from 0.86 down to 0.05.
Overall, researchers concluded, the “results strongly suggest that hatchery-origin strays have lower fitness in the wild,” adding that it is still uncertain, however, whether reduced productivity is environmentally driven, and thus subject to quick changes as environmental conditions shift, “or genetically driven, and likely persistent across generations.”
The study looked only at humpies spawning in Hogan Bay Creek and Stockdale Creek from 2013 to 2016. Both are short streams. Hogan is only about a third of a mile long, and most spawning gravel is in the intertidal reach. Stockdale is slightly less than a mile long with more freshwater spawning habitat.
One of the notable differences found between hatchery fish gone feral and wild spawners was the former’s preference for freshwater spawning. That might have been part of the reason for the much lower spawning success of hatchery strays.
“It is unclear why hatchery-origin fish traveled farther upstream where reproductive success was lower,” the study’s authors wrote. “They may have experienced lower reproductive success because they were strays and were not locally adapted to the spawning habitat. Alternatively, they may have traveled further upstream to less suitable spawning habitat and avoided the intertidal zone because many of the hatchery brood sources came from upstream, freshwater sites and hatchery-origin fish imprint on freshwater sources as embryos and fry in the hatcheries.”
Study lead author Shedd said in an email exchange that there are still a lot of unknowns here, but he added that it is doubtful any loss in wild-salmon productivity can be overcome simply by increasing the number of spawners returning to hatchery-affected streams.
The way fisheries are managed in the Sound today, he said, the spawning grounds are maintained at carrying capacity. A variety of previous studies have found that over-crowding spawning areas decrease spawning success as pinks spawn atop the beds of other pinks and knock eggs out of the gavel.
Still, even if spawning success declines in the Sound due to straying hatchery fish, fishery managers should be able to maintain the same-size returns to wild streams by simply reducing harvests in wild-fish harvest areas given that pinks usually return in numbers significantly greater than are needed for spawning.
Salmon fishery management is entirely built around the idea that salmon returns usually exceed spawning needs and thus produce a “harvestable surplus” of fish in “sustainable fisheries.”
A perfect world
In the ideal scenario, both humans and salmon benefit from sustainable management in that by reducing the so-called “over-escapement” of salmon, the fish surviving to spawn maintain a high rate of productivity.
Hatcheries were designed to boost productivity even further by providing the fish a more stable environment early in their life cycle, and the hatcheries have been very successful at doing so in the Sound.
A peer-reviewed study published in the Canadian Journal of Fisheries and Aquatic Sciences in 2016 reported that since the North Pacific warmed in the 1980s the pink salmon harvest in the Sound “increased nearly tenfold between the low-productivity, prehatchery period and the high-productivity, full hatchery production period.
“Meanwhile, in all other management areas (in Alaska) catch increased approximately threefold. The disproportionate increase in catch observed in PWS compared with the other areas suggests a considerable contribution by the PWS hatchery program, even after accounting for potentially increased wild stock productivity following the shift to improved environmental conditions. ”
The unseen cost of this now appears to have been a loss in some wild watershed productivity due to genetic or epigenetic alterations arising from the domestication of pinks in hatcheries, but it is hard as yet to quantify the size of that loss.
Shedd said the productivity of wild-hatchery hybrid pinks is not yet fully defined, and there is a bigger question revolving around the hybridization that has now been underway for decades. Hybrids are not as successful on the spawning grounds as wild fish, the study indicated, but they are more successful than hatchery fish.
If what was found at Hogan Bay and Stockdale creeks holds true for all streams in the Sound, hybridization would decrease natural production overall, but that would be more than offset by the hatchery production which is orders of magnitude above the historic, natural production of the Sound.
How much the natural production might fall overall will “largely hinge on whether the mechanisms driving reduced reproductive success of hatchery fish are primarily due to genetic mechanisms or to non-genetic mechanisms,” Shedd said.
“For example, if hatchery fish are genetically poorly adapted to successfully reproducing in the wild, then they may pass these poorly adapted traits on to their offspring and it may take generations for (natural) selection to work to increase the reproductive success.
“On the other hand, if the reason why hatchery fish have lower reproductive success is because they are unfamiliar with the stream and don’t know where to spawn (homing wild fish may key in and spawn in the stream section where they emerged), then those effects could be erased in the next generation (poorly selected spawning areas will not produce many fish).
“These are just two examples of these mechanisms – there are lots more postulated in the paper. We are hoping that additional years of data will provide clues regarding the mechanisms and address this important question.”
And the answer to the biggest question is tied up in learning more about how the long-term spawning success of the hybrids.
“We…know that some of the hatchery strays are successfully contributing to the next generation,” Shedd said. “(But) we don’t yet know how their offspring are contributing, so that makes calculating precise proportions of hybrids difficult.”
Also unknown is how long it will take before the Sound is fully hybridized. There remain large variations across the region as to the numbers of hatchery straying salmon, wild salmon and hybrids in streams.
“Both of our study streams located in Southwestern Prince William Sound (PWS) had high proportions of hatchery-origin spawners,” Shedd said. The research was specifically focused there for this reason. Access to a lot of hatchery strays made for better data.
“…Most of the rest of PWS has much lower average proportions of hatchery-origin spawners, so the levels of hatchery introgression are likely much lower. I’d guess that most streams in southwest PWS likely have some degree of hatchery introgression, whereas the streams in eastern PWS, likely have very little hatchery introgression based on the low proportion of hatchery-origin” salmon observed in earlier studies, Shedd said.
Genetic studies are ongoing although some salmon scientists are now wondering if they don’t overlook a far bigger question involving hatcheries – that being the possible effect on Chinook, sockeye and coho salmon when huge numbers of young hatchery pinks and chums are dumped into the ocean every year.
Some scientists have suggested never-before-seen numbers of humpies in the North Pacific may be depressing the number of those big Chinook, the fish Alaskans call “king,” sockeyes; and cohos all along the North American West Coast by grazing ocean pastures down to the terrestrial equivalent of bare ground.
Think of the European rabbits introduced to Australia in the 1800s only to reach a population estimated at 10 billion by 1920, leading to pasture degradation that cost Australian farmers hundreds of millions of dollars in lost production.
Scientists are only beginning to thoroughly examine the abundance of pinks in relation to the declines of other species of salmon to see if they can pin down a cause-and-effect relationship. So far, there are only correlations.
A group of scientists led by Canadian Brendan Connors in 2020 reported finding that “from 2005 to 2015, the approximately 82 million adult pink salmon produced annually from hatcheries were estimated to have reduced the productivity of southern sockeye salmon by 15 percent on average.”
They blamed food competition, but other scientists have argued the real culprit could be ocean-warming due to a changing climate creating a friendlier environment for pinks. They say more evidence is needed to link the declines in sockeye in Canada and the Pacific Northwest to the Alaska pink salmon boom.