Research shows they can enjoy a massage, recognize themselves in a mirror, and get depressed. Are fish welfare standards next?
Fish are about as far away from humans as vertebrates get, evolutionarily speaking: Our last common ancestor lived roughly 450 million years ago.
That gulf limits our compassion for fish — and has made their sentience a subject of long scientific debate. In the 1960s, South African scientist, angler and fierce racist J.L.B. Smith attributed the interest in the possibility of fish feeling pain to “a queer antagonism toward anglers,” and dismissed fish, and fish brains, as too primitive to experience pain. In the decades since, the idea that fish don’t experience pain has remained in the mainstream, even as awareness of the suffering of other animals has grown.
Yet a growing body of scientific work now suggests that fish do experience pain — that in fact, their biological mechanisms for it are “strikingly similar” to that of mammals — and that they exhibit other dimensions of sentience, like experiencing pleasure from a massage, becoming pessimistic after a breakup, and recognizing themselves in a mirror.
Despite that, fish are largely exempt from welfare protections in many places, including the United States. Slowly, that’s starting to change, as scientists and farmers investigate humane treatment and advocates push for better welfare practices. As the number of fish farmed worldwide continues to rise, these welfare standards have the potential to affect the lives — and deaths — of trillions of creatures. But applying them in a watery realm that’s unlike ours is a challenge.
***
Fish are unlike us, but they’re essential to our diets; an estimated 10 to 100 billion farmed fish are harvested globally every year, with trillions more caught in the wild, and that number is increasing — the Food and Agriculture Organization of the United Nation estimated global aquaculture production at 104.1 million tons in 2025, up 2.7 percent from the year before. In 2022, aquaculture surpassed fisheries as the main source of seafood.
Until recently, how those animals were faring has slipped under the radar; in the United States, fish are not protected from inhumane treatment under the Animal Welfare Act, despite being consumed in far greater numbers than land animals. In other countries, including Canada, protections are piecemeal, varying between provinces and species.
Some fish farmers are making changes nonetheless.
Cedar Crest Fish Farm, which operates under the brand name Springhills Fish, has been farming fish in southern Ontario for decades, and now produces rainbow trout, arctic char, coho salmon, and lake whitefish. Some of their breeding lines for rainbow trout go back 80 years, and are “part of the family,” said Arlen Taylor, the farm’s co-owner.
None of this definitively proves pain — without a way to communicate, we can’t know what is unfolding in a fish mind. But research to address suffering is nonetheless moving ahead.
Taylor, who took over operation of the farm from her father, said that in working closely with the fish, it’s obvious to her that they’re sentient, and have the capacity to experience feelings such as pleasure and pain.
“I can stick my hand in a tank with my breeders and they’ll come and they’ll bop me and say hi. So the question of sentience for us has never been a question. They have always been sentient beings.”
Springhills Fish has been proactive with that knowledge, Taylor said. Before welfare became a buzzword, they made changes to keep their fish happy, from ensuring appropriate diet and water chemistry to respecting social dynamics.
“We’ve learned over the years to keep them comfortable,” she said. By protecting fish well-being, Taylor said the operation also runs more smoothly.
Yet pinning down what well-being means to a fish is a difficult question. One dimension has to do with the fundamental difference between fish and terrestrial animals.
In aquaculture operations and wild-caught fisheries, fishes’ ability to breathe is not guaranteed — water breathers need access to sufficiently oxygenated water, and in aquaculture enclosures, or in a warming ocean, low dissolved oxygen levels can harm or kill fish.
In December, a paper published in Issues in Science and Technology argued that breathing should be considered alongside the five freedoms — internationally accepted standards that set out a baseline for humane treatment.
“It’s clear in the welfare science that we have this terrestrial bias, this air-breathing bias,” said the paper’s co-author, Jennifer Jacquet, professor at the University of Miami. “As terrestrial mammals put a lot of emphasis on eating … but water breathers, they’re constantly worried about where they’re going to get oxygen.”
A study published in Nature in June estimated that, based on the available evidence (including behavioral indicators and neurophysiological measures) a rainbow trout killed by air asphyxiation experiences around 10 minutes of moderate to intense suffering. The authors noted that even 60 seconds of air exposure was enough to trigger a negative physiological response greater than that caused by longer-lasting stressors like handling and crowding.
“We see this transition: Fish are walking the path that the chickens did 20 years ago.”
The fact that oxygen is nonetheless not considered a core part of animal welfare is a blind spot, said Jacquet, who has also pointed out that the idea that fish don’t feel pain has been historically driven by commercial seafood interests.
Until the early 2000s, little scientific work had gone into answering the question either way. But in 2003, a researcher named Lynne Sneddon published research showing that fish had nociceptors — the neurons that help detect damage to the body. Other research has also shown that fish will show behaviors associated with pain, including rubbing areas injected with acid against the gravel, or avoiding areas of tanks where they’d received electric shocks.
None of this definitively proves pain — without a way to communicate, we can’t know what is unfolding in a fish mind. But research to address suffering is nonetheless moving ahead.
Albin Gräns, associate professor at the Swedish University of Agricultural Sciences, is investigating a range of welfare practices, including a survey of welfare practices for Mediterranean seabass and an investigation of humane slaughter techniques for channel catfish — such as stunning with a pressure wave or rapidly heating up the brain with a laser — as part of a project run by the Center for Responsible Seafood.
Gräns said many of the standard practices for treatment of farmed fish were designed for the comfort of human handlers, not the fish — for instance, the practice of stunning fish by putting them in ice. These fish appear unconscious, said Gräns, but his work has shown the fish are simply paralyzed, while still aware and highly stressed. He said people are slowly moving away from that practice, as understanding of fish physiology grows. “We see this transition: Fish are walking the path that the chickens did 20 years ago.”
Of course, for chickens and other terrestrial farmed animals, welfare isn’t exactly guaranteed. In much of the United States for instance, procedures such as castration of pigs and cattle generally take place without pain management. And in his work, Gräns said it’s become clear that in any industrial-scale system, the well-being of the animal isn’t top priority. Still, advocates say the mind-boggling number of fish affected makes it important to consider their welfare.
These advancements are about more than slaughter. For fish to be truly faring well, they need to be able to live as they would in their natural habitat, said Yannick Rohrer, aquaculture specialist for Fair Fish, an organization dedicated to improving fish welfare.
Welfare standards for wild-caught fish, while promising, are “eons” from being applied.
Fair Fish has compiled a database of almost 100 farmed species, to assess their welfare in common farming methods, using a set of 10 parameters. One parameter that farmers are just starting to consider is enrichment, Rohrer said; many fish naturally live in complex environments, but are reared in barren tanks, nets, or raceways. Increasingly, research suggests that giving fish something to interact with improves their welfare, boosting growth and reducing aggression.
Rohrer is currently working with producers of rainbow trout in Switzerland, to experiment with whether putting simple stimulation inside tanks, in the form of hanging bars, can improve well-being. “That would also be one of the first … practical experiments to show that it is feasible to put structural enrichment into farms and still work normally and produce normally,” he said. “We desperately need some practical validation.”
The next welfare frontier is wild-caught fish. Many of the animals caught in fisheries die horrible deaths, if the research on fish pain is any indication. Fair Fish is beginning work with harvesters to implement methods to minimize suffering, and Gräns is researching methods to address welfare concerns, including whether electrical stunning can be used to kill wild fish, rather than air asphyxiation. There are significant practical challenges in this, Gräns said — but there’s also growing receptiveness to the idea of welfare.
“There are a lot of people that need to be convinced. But every time I go out, I’m surprised by how few there are left.”
But for Arlen Taylor, aquaculture deserves special focus. Welfare standards for wild-caught fish, while promising, are “eons” from being applied, she thinks. In the meantime, it’s important that aquaculture be recognized as having more in common with farming, Taylor said — and that fish get the same protection as terrestrial livestock.
Fish farmers still have work to do in that respect, she said. But the public also needs to get on board.
“The irony being that the general public … is still questioning the sentiments. I would love to see that belief system completely demolished.”
