Fish Are Smarter Than You Think

Guppies (Poecilia reticulata)

Source: Per Harald Olsen, via Wikimedia Commons

Can we finally retire the myth that goldfish have three-second memories? This oft-cited “fact” has been thoroughly debunked. Scientists have shown that fish can distinguish and remember individuals, navigate with mental maps, cooperate and communicate with one another, build complex structures, use tools, and keep track of quantities. There are scores of studies supporting the impressive learning abilities and sophisticated behaviors of fish.

But we may still be underestimating fish cognition, according to a recent paper in the journal Methods in Ecology and Evolution.

“When we say ‘fish,’ we are talking about over 30,000 species,” says Catarina Vila-Pouca, an ecologist at the Centre d’Ecologie Fonctionelle et Evolutive in Montpellier, France, and one of the study’s authors. “Most of the research that has been done so far has focused on a handful of species that are very well-studied.”

In addition to overlooking the majority of species, most studies on fish cognition have been conducted in controlled laboratory environments, often with lab-raised fish. Although lab-based studies have yielded important discoveries, the results may not always generalize to the wild. In the artificial environment of a lab tank, fish may experience more stress and less motivation to exhibit complex behaviors. As a result of these limitations, findings from lab-based studies may not accurately capture the full complexity of how fish learn and behave in their wild environment.

Taking the Test to the Fish

To address this imbalance in the scientific literature, Vila-Pouca and colleagues developed a way to bring the rigor of the lab into the natural habitats of more fish species. With co-first author Hannah De Waele, senior authors Alexander Kotrschal and Amy Deacon, and several master’s students, Vila-Pouca designed and tested a new interactive cognitive apparatus for use with wild fishes.

“We wanted to create something easy and flexible and that could be used in different environments and with different species,” says Vila-Pouca. “It was also important that it be cheap and quick to set up and very adaptable.”

The new apparatus, a kind of foraging board, is a 30 by 30 centimeter plate with 24 small holes, each covered by a pivoting disc that a fish can nudge aside to access a food reward hidden below. Researchers can adapt the foraging board to test different abilities; for instance, by marking the rewarded discs with different colors, shapes, or dots of varying number or size, they can probe a fish's discrimination learning, memory, and numerical abilities. Other potential uses include the study of spatial learning and memory, social learning, and decision-making.

Nine-spined stickleback (Pungitius pungitius)

Source: Piet Spaans, via Wikimedia Commons

For initial testing, Vila-Pouca and colleagues deployed the foraging board with wild fish species in two different habitats: guppies (Poecilia reticulata) in Trinidad’s tropical Aripo River and nine-spined sticklebacks (Pungitius pungitius) in a temperate freshwater pond in the Netherlands.

“The fish were quite fast in coming and getting the food, and their learning rates were similar to what we’ve found in the lab, showing that the board works and that the fish interact with it,” says Vila-Pouca.

These field tests of the apparatus also revealed interesting species differences. In Trinidad, some guppies consistently excelled at using the foraging board. These fish, called “producers” by the researchers, solved the task more frequently and adapted their approach based on previous successes. Meanwhile, other guppies, dubbed “scroungers,” rarely tried to engage with the foraging board. Rather, they waited for a producer to uncover a reward and then swooped in to steal it.

In the Netherlands, a different pattern emerged among the sticklebacks. Almost all of them investigated the foraging board themselves rather than scrounging. Though most sticklebacks ended up learning the task, they varied in how long it took them to grasp the concept.

Fish Appreciation

Vila-Pouca and colleagues emphasize the versatility of their new testing apparatus. They see the potential of this simple yet effective design for studying different research questions in fish species living in a variety of habitats.

What’s the point of probing the intelligence of different fish? Vila-Pouca says that fish are a good group in which to study big questions in ecology and evolution; there are so many species living in different types of environments and with different life histories. This diversity allows scientists to go beyond asking, ‘Can fish learn this?’ They can instead investigate what social or physical environments drive certain types of learning.

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In addition, the study of fish cognition has implications for the care of captive fish. Vila-Pouca says she hopes research like this helps change public perception and drives changes in how people treat fish.

“I think there's still a lot of work to do in terms of communicating findings and showing the public that fish are smart and they can learn all sorts of things,” she says. “It's difficult because we don't come into contact with fish so much. They don't have the facial expressions that we are used to in animals more similar to us. We don't hear them vocalizing. I think it would be nice if people would try to spend more time with fish and really look at their behavior. Maybe they would empathize with them a bit more.”

Trinidadian guppies.

Source: Amy E. Deacon, Hideyasu Shimadzu, Maria Dornelas, Indar W. Ramnarine, Anne E. Magurran, via Wikimedia Commons