Fish Intelligence

I wrote this when I served as Mercy For Animals’ (“MFA”) [sic] director of investigations. I worked with them through 2012.

Fish Intelligence

Humans are just beginning to understand fish intelligence and pleasure. Consideration of fishes’ complexities is long overdue. In a section titled “Misunderstood Fish” of his book Second Nature: The Inner Lives of Animals, world-renowned animal behaviorist Dr. Jonathan Balcombe states:

The common view that fishes are unfeeling robots with fins is becoming outdated in the face of emerging studies. Forty years ago, the idea of producing a book devoted to the mental and emotional qualities of fishes was unthinkable. Science wasn’t ready to accept, let alone study, fishes in those contexts. Times have changed. … We have many prejudices about fish. … Fish didn’t stop evolving when the first lobe-finned member of their kind ventured onto land and established the terrestrial vertebrate lineages. Fishes encompass a diversity of perceptual, mental, emotional, and cultural phenomena.i

University of Macquarie Biologist Dr. Culum Brown, an expert in the evolution of fish cognition, behavior and ecology, concludes:

Fish are more intelligent than they appear. In many areas, such as memory, their cognitive powers match or exceed those of “higher” vertebrates, including nonhuman primates.ii

In the journal Fish and Fisheries, Dr. Brown, along with Dr. Kevin Laland, expert in behavioral and evolutionary biology, and Dr. Jens Krause, expert in behavioral ecology and Head of Biology at the Leibniz-Institute of Freshwater Ecology and Inland Fisheries, assert:

[F]ish are regarded as steeped in social intelligence, pursuing Machiavellian strategies of manipulation, punishment and reconciliation, exhibiting stable cultural traditions, and co-operating to inspect predators and catch food.iii

Dr. Balcombe dedicates a section of his book Pleasurable Kingdom: Animals and the Nature of Feeling Good to a discussion of fishes’ intelligence and capacity to suffer, feel pain and experience pleasure. He notes:

[F]ish representatives recognize individual “shoal mates,” acknowledge social prestige, track relationships, eavesdrop on others, use tools, build complex nests, and exhibit long-term memories.iv

His review of scientific studies and observations of fish from around the world include fascinating accounts of these complex animals that most of us will never experience firsthand. For example, fish that inhabit rocky tide pools have been shown to memorize complex topography during high tides, such that in low tides they can safely jump from one area of pooled water into another. They have also been observed to choose mates wisely, based on traits that older fish have come to value given their life experiences. Dr. Balcombe writes that the studies on fish “indicated the ability to scrutinize, compare, remember, recognize individuals, make subtle discriminations, and of course to make decisions.”v

Dr. Balcombe’s Pleasurable Kingdom includes further, fascinating information on fish:

Fishes are surely curious. They are known to cautiously investigate novel objects in their surroundings. Anyone who has had their legs nibbled at by schools of little fishes … has experienced their inquisitive nature. … Behavior consistent with some definitions of play – including manipulating and balancing objects, leaping, and chasing games – has been reported across disparate groups of fishes. There are many accounts of fishes leapfrogging, sometimes repeatedly, over floating objects, including turtles. Play-like jumping and leaping behavior is known from at least six different families of fish. Many readers will have witnessed one or more fishes repeatedly leaping clear of the water in a lake or pond.vi

Dr. Balcombe describes fish juggling objects and even swimming to “gulp air at the surface of their tank, swim to the bottom, release the air and chase the bubbles to the surface.”vii Over the past decade, the breadth of literature looking at the mental and emotional lives of fish has expanded. But as limited as our current understanding of fish intelligence and sentience is, it is nevertheless obvious at this point that they possess both, and accordingly, deserve to live free of unnecessary suffering.

To learn how you can help fish, click here.


i Balcombe, Jonathan. 2010. Second Nature: the Inner Lives of Animals. Palgrave Macmillan: New York.
ii Brown, Culum. 2004. Not just a pretty face. New scientist, 2451: 42-43.
iii Laland, K with Brown, C. and Krause, J. 2003. Learning in fishes: an introduction. Fish and Fisheries, 4, 199-202.
iv Balcombe, Jonathan. 2006. Pleasurable Kingdom: Animals and the Nature of Feeling Good. Macmillan: New York.
v Id.
vi Id.
vii Id.

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