Whether roaming wild or enclosed in floating feedlots on the ocean, Atlantic salmon are cold-water fishes. But because the climate crisis warms the world’s oceans and waterways, cold water is becoming harder to seek out, which implies these long-endangered fish are facing perhaps their biggest challenge yet.
Atlantic salmon are anadromous, moving between freshwater and saltwater environments. For millennia, they spawned within the rivers of the northeastern United States, eastern Canada, and Northern Europe before migrating to the coasts of Greenland and Iceland. There, they grew to maturity before returning to their natal rivers to offer birth to recent generations.
The journey has long been perilous. Pollution, dams, overfishing, and habitat destruction have diminished the variety of Atlantic salmon for the reason that dawn of the Industrial Revolution. Salmon runs that when numbered within the tens of hundreds of thousands have disappeared, and wild salmon have nearly disappeared from all of their ancestral waters. Climate change poses a potent recent threat to each wild salmon and people contained inside industrial pens.
For twenty years, researchers have documented far-reaching damage to ocean ecosystems from rising water temperatures. Figures from the North Atlantic Salmon Conservation Organization, a nonprofit, illustrate one aspect of the impact. Prior to 1990, only a single fish out of 1,000 fertilized eggs survived its first 12 months at sea. From 2007 to 2016, that single salmon required 2,000 eggs.
NOAA warns that climate change represents a possible extinction-level danger to some species of untamed salmon.
The danger extends beyond the marine environment. A study by the state of Washington in 2020 found that because the air warms, snowmelts dwindle, and droughts increase, less cold water stays in streams and rivers in summer, when salmon need it essentially the most.
Warmer water also incorporates less oxygen, which makes it harder for salmon to breathe. Temperatures above 64 degrees F (18 degrees C) speed up the salmon’s metabolism, increasing the necessity for oxygen and forcing the fish to expend more energy to swim farther looking for food and cooler water.
With global warming predicted to accentuate, the National Oceanic and Atmospheric Administration has warned that climate change represents a possible extinction-level danger to some species of untamed salmon.
Bill Taylor, president of the Atlantic Salmon Federation, a nongovernmental group dedicated to protecting wild salmon and restoring their habitats, shares that fear. “Climate change is the largest impact without delay on salmon, and it would be for a long time to return,” Taylor told us. “It has a direct impact from the headwater streams to the feeding grounds off western Greenland. Salmon is only one species affected by climate change, but we see it because the canary within the coal mine.”
A salmon farm off the Faroe Islands within the North Atlantic.
Martin Zwick / REDA&CO / Universal Images Group via Getty Images
Wild salmon have struggled against the percentages for a long time and now must adapt yet again. Marine biologists have recently tracked each Pacific and Atlantic salmon to the Arctic looking for colder water. These so-called “thermal migrants” could open a recent chapter within the evolution of this keystone species, provided the fish can adapt before the climate clock runs out.
Farmed salmon, after all, face similar climate-related pressures. But unlike their wild relatives, they don’t have any hope of migrating to cooler water. Since farmed salmon cannot adapt, the aquaculture industry itself must change — or face its own decline.
The danger to the industry was explained concisely in Dead Loss, a 2021 study by Just Economics, a research organization in the UK. “Atlantic salmon can only be farmed under certain conditions and as seas warm and available locations turn out to be exploited, the industry is running out of viable sites for brand spanking new farms,” the study said. “Which means that recent sources of growth are dwindling, creating pressures to locate farms in less suitable environments and to extend stocking densities, which further exacerbate environmental pressures.”
We spent two years examining the practices of the $20-billion global salmon farming industry for our recently published book, Salmon Wars: The Dark Underbelly of Our Favorite Fish. We interviewed scientists, physicians, environmentalists, and other people within the aquaculture business. Climate change emerged as one of the vital critical environmental and fish welfare challenges to salmon farmers, raising doubts in regards to the industry’s future on the warming oceans.
A 2019 die-off of farmed salmon in Canada was primarily brought on by higher water temperatures, researchers say.
Since its origins within the late Sixties and early Nineteen Seventies in Norwegian fjords, open net pen salmon farming has turn out to be the world’s fastest-growing food sector, providing as much as 90 percent of the Atlantic salmon eaten in North America. A handful of multinational corporations dominate the business and produce 96 percent of the world’s farmed salmon in 4 regions — Norway, Chile, Canada, and Scotland. Small numbers of farms are positioned off the coasts of Maine, Ireland, Tasmania, and the Faroe Islands.
The industry’s rapid expansion and intensive farming methods have generated considerable controversy. While the industry promotes its product as sustainable, some scientists and conservation groups query the farms’ impacts on each the environment and fish welfare.
A typical open-net pen salmon farm consists of 12 to 16 cages produced from reinforced plastic nets, that are roughly 400 feet in circumference and about 30 feet deep. The nets are suspended by floatation collars and attached to the seabed by steel cables, which permit the installation to maneuver with the present and tides. A single farm can hold one million or more salmon.
From the surface, salmon farms appear innocuous. Below the water line, cages are so crowded that they turn out to be breeding grounds for viruses and diseases. Because farms are sometimes positioned on salmon migration routes, the spread of diseases and parasites like sea lice endanger wild fish. Excess feed, excrement, and residue from pesticides and other chemicals often accumulate below the farms.
Salmon killed in a mass die-off at Porcelana farms in southern Chile in 2021.
ALVARO VIDAL / AFP via Getty Images
The issues created by industrial-scale aquaculture have increased in tandem with ocean temperatures. The clearest impact will be seen within the increasing number and size of mass mortalities at salmon farms in eastern Canada, Norway, Chile, and Ireland, in response to a study by Spheric Research, a consultancy specializing in sustainable food systems.
Mortality rates for farmed Atlantic salmon are estimated at between 15 and 20 percent globally. (Against this, factory chickens have a mortality rate of 5 percent.) But lately the salmon industry has, in some places, suffered far higher rates.
A record die-off occurred in late summer of 2019 off the southwestern coast of Newfoundland, wiping out 2.6 million fish at 10 of Northern Harvest Sea Farm’s operations — nearly half of the operator’s fish. The corporate blamed the deaths solely on an prolonged period of ocean temperatures reaching 70 degrees F (21 degrees C). Because the surface water warmed, the fish sought refuge in cooler water at the underside of the cages, where they suffocated from lack of oxygen.
The Fisheries and Marine Institute at Memorial University investigated the die-off and located the rise in water temperatures was the first cause. But warmer water, the study said, was just one element in a “spiral of worsening conditions” contained in the net pens. The usage of pesticides to fight parasites had stressed the fish before the arrival of the nice and cozy water, and algae blooms within the bays had further depleted oxygen levels.
Scientists have no idea if wild salmon can move to cooler water fast enough to survive warming oceans.
Similar concerns have been raised elsewhere. A 2021 study within the Journal of Marine Science concluded that warmer water was increasing infestations of sea lice and rendering the standard pesticides ineffective. A 2022 study by the U.S. Environmental Protection Agency found warming water also increases the frequency of harmful algae blooms. The agency noted that marine animals must leave the affected areas to survive. Again, farmed salmon don’t have that option.
The industry counters critics by claiming that salmon farms can meet the world’s growing protein crisis. A study by the University of British Columbia’s Institute for the Oceans and Fisheries, nonetheless, predicted that aquaculture production — including farmed salmon — in lots of locations and under a high-emissions scenario will drop by as much as 90 percent by mid-century on account of the direct impact of ocean warming and the indirect damage to forage fish, essential to the industry as salmon feed.
Some multinational salmon farming corporations are racing to get ahead of warming oceans. Rival corporations in Norway are fighting to maneuver their farms to the country’s northernmost fjords. Innovasea, based in Boston, has developed a submersible fish pen that will be lowered to avoid warm surface water and keep fish at optimal temperatures. Researchers in Norway and Australia are taking one other route, attempting to breed salmon that might higher resist heat.
Fish Farm, within the United Arab Emirates, is certainly one of a growing variety of land-based projects where Atlantic salmon are raised in tanks.
GIUSEPPE CACACE / AFP via Getty Images
Meanwhile, a radical alternative to ocean salmon farms is emerging. Recirculating aquaculture systems, referred to as RAS, raise Atlantic salmon in large tanks on land. The water is filtered to remove contaminants, allowing the fish to grow without chemicals. The closed-containment systems be certain that the fish never touch the ocean, which erases any threat to wild salmon or other marine life.
Independent RAS projects are popping up in landlocked places, including Switzerland and the United Arab Emirates. The most important plant, called Atlantic Sapphire, lies about 13 miles inland from Florida’s east coast. Essentially the most modern plant could also be Superior Fresh, in Wisconsin, which raises its salmon only in freshwater, allowing the power to recycle the nutrient-rich water to a virtually 13-acre greenhouse that hydroponically produces leafy green vegetables.
Nobody knows whether wild salmon can move to cooler water fast enough to avoid succumbing to warming oceans. But some who’re studying the brand new movements are optimistic.
“Salmon have a tremendous ability to adapt to harsh conditions,” said Karen Dunmall, a marine biologist with Canada’s Department of Fisheries and Oceans who studies salmon migration northward. “Salmon are doing what salmon do. They access recent places and check out to work out how they’ll establish themselves.”
