A new study of zebra danios (Danio rerio), a popular fish found in freshwater aquariums around the world, claims that fish can feel emotions, which the researchers call “emotional fever.”
Dr Sonia Rey, of the Institute of Aquaculture, University of Stirling in The United Kingdom, and a lead author of the study, says that the findings are interesting in that emotions had only been found in mammals, birds, and certain reptiles, but never fish.
“Expressing emotional fever suggests for the first time that fish have some degree of consciousness.”
So how did the researchers conclude that fish have feelings too? They took 72 zebra danios, divided them into two equal groups and then put them in a fish tank that featured different connected compartments, but with varying temperatures. These temperatures ranged from 64ºF to 95ºF. They then placed a control group in an area of the tank that had their preferred temperature, 82ºF. The remaining zebra danios were out into a stressful situation for 15 minutes in which the water was one degree cooler.
The control fish stayed in the 82ºF compartments while the fish that were subject to the cooler water swam into the compartments that had higher temperatures, which increased their body temperatures by 36 to 39ºF. The researchers believe that these actions by the fish is proof that they were displaying emotional fever.
While the link between emotion and consciousness is still debated, this finding removes a key argument for lack of consciousness in fishes, Rey said.
Our results 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.
So do zebra danios have emotions? Or will they always swim to the warmer part of a fish tank to warm up?
The study was published in the journal Proceedings of the Royal Society B: Biological Science.