STIRLING, England, Nov. 25 (UPI) -- Whether or not fish are sentient beings remains a difficult and unresolved question -- part ethics, part biology -- but new research may offer some clarity on the matter.
Many scientists have excluded fish from the sentience accorded to mammals, birds and reptiles due to their inability to generate an "emotional fever." An emotional fever is a literal fever, an elevation of body temperature of about 1 to 2 degrees Celsius in response to stress. It's been used as a baseline proof of consciousness in other species.
New findings by scientists in England and Spain show some fish species may experience an emotional fever.
Scientists inferred the presence of an emotional fever by studying the behavior of 72 zebrafish in response to stress. Half of the zebrafish were placed in a net and dunked in a tank of water 1 degree Celsius colder than they are used to. The other fish, the control group, remained in an unchanged tank. All the fish were then put in a tank with differently heated regions and allowed to swim freely.
The recently stressed fish congregated in the heated sections, raising their body temperatures from 2 to 4 degrees Celsius -- which scientists say demonstrates emotional fever.
Researchers published their findings in the journal Proceedings of the Royal Society B.