Fish

Fish feel pain, and we kill more than a trillion of them a year

By WhyStopHarmingAnimals.com

Fish are the most killed animals on the planet, and they feel pain[5][6][7]. The recorded wild catch alone is estimated at 1.1 to 2.2 trillion fish a year[1]. At a midpoint near 1.6 trillion, that is about 4 billion wild fish every day[1]. Fish farms kill about 130 billion more each year[3]. Most of these animals die by suffocation or crushing, and the research on their nervous systems and behavior shows there is someone there to experience it[5][6][7].

The largest killing on Earth

FAO, the UN's food agency, counts fish in tonnes[1]. Mood and Brooke turned those recorded landings into numbers of individual fish and published the result in Animal Welfare in 2024[1]. Averaged over 2000 to 2019, they estimate 1.1 to 2.2 trillion wild finfish caught each year[1]. For 2019 the figure was 980 to 1,900 billion, still about 87% of all vertebrate animals killed for food or feed.

That estimate covers recorded catch only[1]. It excludes illegal fishing, discarded bycatch, and ghost fishing by lost gear[1], so the true number is higher. The authors recommend that FAO report numbers of animals, not just tonnes.

Around half of the recorded wild catch, hundreds of billions of mostly small fish, is ground into fishmeal and oil[1] rather than eaten by people. Much of it is fed to farmed animals, farmed fish among them. Underneath a fillet of farmed salmon is a pile of wild fish.

Fish farming has grown fast[3]. A peer-reviewed estimate in Animal Welfare in 2023 put the number of farmed finfish killed in 2019 at 78 to 171 billion[2], with a midpoint of 124 billion[2][3], a nine-fold rise since 1990[3]. Pond loach, Nile tilapia and carp dominate the count[2]. Fishcount's update for 2022 is about 130 billion, with a range of 86 to 180 billion[3]. Chickens, the most killed land animal at about 78.5 billion a year, are outnumbered by farmed fish alone.

Fish feel pain

In 2003, Lynne Sneddon and colleagues recorded from nerves in the heads of rainbow trout and found polymodal nociceptors, pain receptors that respond to pressure, heat and acid, with properties like those in mammals and other higher vertebrates[5]. The study was published in the Proceedings of the Royal Society B[5].

A second study that year, in Applied Animal Behaviour Science, injected acid or bee venom into trout lips[6]. The fish rocked from side to side, breathed faster and stopped eating[5][6], and the changes lasted for hours[5]. When the trout were given morphine, those pain-related behaviors dropped significantly[6]. A painkiller changing behavior like that is more than a simple reflex would explain, and the authors concluded as much[6].

Culum Brown's 2015 review in Animal Cognition goes further[7]. Perception and cognition in fish often match or exceed those of other vertebrates, with evidence for pain, social intelligence, long-term memory and tool use[7]. As Brown puts it, the public picture of fish is decades behind the data[7].

Some fish recognize themselves

Bluestreak cleaner wrasse are small reef fish. In a 2019 study in PLOS Biology, Kohda and colleagues put a mark on their throats, visible only in a mirror[8]. The fish tried to scrape it off, but not when the mark was clear or when there was no mirror[8]. That is the behavior scientists read as passing the mark test[8]. A 2022 follow-up with a more natural-looking mark increased confidence in the result[8].

Later work found cleaner wrasse can recognize their own face in photographs[9]. A 2025 study in Scientific Reports found some fish responding to the mark within the first hours of mirror exposure, and some dropping shrimp in front of the mirror to watch how the reflection moved, testing how the mirror works[10]. Other recent work shows them using the mirror to check their own size before deciding whether to fight. These studies use small numbers of fish, but together they give fish some of the strongest experimental support for mirror self-recognition of any animal outside mammals and birds.

Tools and teamwork

Fish use tools[7][11]. A wrasse called the tuskfish (Choerodon schoenleinii) was filmed smashing a clam against a rock anvil, a finding published in Coral Reefs in 2012 from a single observation[11]. Other wrasses do the same with shellfish. Archerfish knock insects off leaves with jets of water, a skill they learn, partly by watching other archerfish. Groupers and moray eels signal to each other and hunt together.

How they die

Most wild-caught fish die in nets or on deck, crushed or suffocated. Many farmed fish are killed in air or in ice slurry.

The New York Declaration on Animal Consciousness, published in 2024, holds that there is at least a realistic possibility of conscious experience in all vertebrates, fish included, and that it is irresponsible to ignore that possibility in decisions that affect them[12]. Fish are vertebrates[12]. Calling them "just fish" is how the largest killing on the planet stays easy to ignore.