A new study has found that fish have emotions. The study, published in Proceedings of the Royal Society B, found that zebrafish responded to stress by an increase in body temperature, or what it known as an “emotional fever.” It’s been suggested that such a thing only exists in mammals, birds and reptiles, but the new research proves otherwise.
Scientists placed six zebrafish groups in tanks divided by plexiglass into six chambers, each containing water of a different temperature. Each tank was connected, so the fish were able to access them all and then were allowed to acclimatize to the water overnight. Then the scientists confined three groups of fish using a small net, which brought on stress. Afterwards, they released the fish into the central chamber and examined their movements. According to the study, the results were “striking.” The researchers found that while the unconfined groups remained where they were, the stressed zebrafish spent significantly more time at higher temperatures, which led to an estimated rise in body temperature, and therefore an emotional fever. “This finding,” they wrote, “removes a key argument for lack of consciousness in fishes.”Though previous studies have shown that fish, despite their small size, are pretty smart when it comes to using tools, navigating waters and recognizing social hierarchy, this is the first time research has suggested they are also sentient beings.
Scientists differ on the degree to which fish can have consciousness. Some researchers argue that they cannot have consciousness as their brain is simple, lacking a cerebral cortex, and they have little capacity for learning and memory, a very simple behavioral repertoire and no ability to experience suffering. Others contest this view, pointing out that, despite the small size of the fish brain, detailed morphological and behavioral analyses have highlighted homologies between some of their brain structures and those seen in other vertebrates, such as the hippocampus (linked to learning and spatial memory) and the amygdala (linked to emotions) of mammals. In the words of Sonia Rey, of the Institute of Aquaculture, University of Stirling and the UAB’s Institute of Biomedicine and Biotechnology (IBB), “these findings are very interesting, expressing emotional fever suggests for the first time that fish have some degree of consciousness”.
“Our results add to the emerging picture of fish as behaviorally complex animals that may well be sentient and conscious to an extent at least,” the researchers wrote in the publication. The scientists also mentioned that their findings could have bearings on how fish are treated, given that some species have shown signs of experiencing feelings. “They therefore have important implications both for how the welfare of fishes is conceptualized and protected and for our understanding of the evolution of emotions and consciousness in vertebrates,” the scientists added.The group said the research could be particularly useful in regards to fish farms and protecting the welfare of the fish
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