School Fish By Enriching Their Habitat

By Christie Wilcox | August 2, 2013 8:00 am
Smart fish

Don’t let his looks fool you — this goldfish is probably smarter than your average bowl variety because his tank is decked out!
Image credit: sbotas

Think that little plastic castle in your goldfish tank is just decoration? Not so, say scientists. Having such obstacles and spatial variety might be making Goldie smarter.

When humans first started keeping animals in captivity, we kind of sucked at it. Even when we met an animal’s every obvious need — nutrition, water, shelter, etc — some just didn’t do well. As we learned more about the minds of animals, we realized that they needed more than sustinence, and the concept of enrichment was born. Since the 1980s, captive animal facilities have been required to provide an adequate physical environment to promote the psychological well-being of species like primates and marine mammals. Most zoos and aquariums go above and beyond the mandate, insisting that the animals’ emotional and mental health is paramount. The Association of Zoos and Aquariums even goes as far as to state that enrichment is “as critical to an animal’s well-being as having the right food and medical care.”

Usually, the focus is on the smarter animals, with enrichment entailing activities like giving monkeys toys to play with, or placing an octopus’ dinner in a sealed jar for it to open. Fish aren’t exactly known for their smarts, but that doesn’t mean they won’t benefit from an enriched environment, too. New research has found that fish brains are boosted when humans add a little variety and diversity to their life, and this knowledge may help conserve key species.

The international team of researchers led by Penn State’s Victoria Braithwaite studied how the brains of juvenile Atlantic Salmon developed based on the environment they are raised in. Some of the fish they raised in your classic aquaculture tanks — boring, simple, and unadorned. Others they enriched with rocks and plants to create a three-dimensional environment much more akin to what these fish would experience in their native habitat. They then tested the fish’s smarts by seeing how quickly they could escape from a maze. They reported their results in this week’s issue of the Proceedings of The Royal Society B.

The fish raised in the enriched tanks made fewer errors and escaped the maze much faster than their counterparts. “That enriched fish made fewer mistakes suggests that they were better at learning and then improving their performance through a trial-and-error process during the 7 days of testing,” explain the authors. This cognitive improvement correlated to increased expression of NeuroD1 in their forebrains, a transcription factor associated with neurogenesis and memory in a number of vertebrate species. This is the first time an effect of enrichment has been found to positively facilitate both neural plasticity and spatial learning in fish.

The team hopes that their research and the growing body of literature on fish will help hatcheries and aquariums raise smarter, healthier fish. For wild restocking programs, such increased intelligence could make the difference between success and failure. The United States rears millions of fish every year in an attempt to boost popular fisheries species and restore depleted populations. In New York State alone, roughly 1 million pounds of captive-raised fish are released every year. But there is a problem with populating wild stocks from captive-bred fish: the ones raised in tanks don’t fare well in the real world. “Animals that are reared in captivity and subsequently released are at a considerable disadvantage because they are behaviorally ill-equipped to deal with the novel environment,” explain the authors.

“The philosophy of most fish hatcheries is to rear a large number of fish and hope some survive,” said Braithwaite. But if the fish were smarter, you might not need so many of them. “What this study is suggesting is that you could raise fewer, but smarter fish, and you will still have higher survivability once you release them.”

This study also suggests that proper enrichment may help keep aquarium fish happy and healthy, from the largest sharks to the smallest guppies. Hobby aquarists take note: a few new ornaments or moving around things in a tank will keep your pet fish’s brain engaged. Of course, you might not want your fish to be too much smarter — if they’re anything like mine, a little brain boost might be a bit of a mess…



Citation: Salvanes A.G.V., Moberg O., Ebbesson L.O.E., Nilsen T.O., Jensen K.H. & Braithwaite V.A. (2013). Environmental enrichment promotes neural plasticity and cognitive ability in fish, Proceedings of the Royal Society B: Biological Sciences, 280 (1767) 20131331-20131331. DOI:


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About Christie Wilcox

Dr. Christie Wilcox is a science writer based in the greater Seattle area. Her bylines include National Geographic, Popular Science, and Quanta. Her debut book, Venomous, released August 2016 (Scientific American/FSG Books). To learn more about her life and work, check out her webpage or follow her on Twitter, Google+, or Facebook.


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