Salmon swim better when they're happy

UMEå, Sweden, Dec. 6 (UPI) -- For humans, depression and anxiety can inhibit physical health and performance. The same is true for salmon, new research suggests.

Experiments by researchers in Sweden suggest anxiety can depress a salmon's urge to migrate. To grow, mature and reach their full physical potential, young salmon must swim downstream from the freshwater environs of their birth to the ocean. Some are more eager than others for the journey.

Previous studies have suggested current strength, light and temperature all play roles in coaxing a salmon to migrate. But much intraspecies variation remains unexplained.

Researchers at Umeå University presented salmon in the lab with the opportunity to migrate down an artificial stream. Scientists also measured the willingness of salmon to migrate down a natural stream in Northern Sweden. Salmon treated with anxiety medication were twice as likely to make the downstream journey.

Interestingly, the dosage of medication used was lower than the levels found in some wastewater.

"Even though salmon in Northern Sweden live in river-systems low to moderately affected by contaminated wastewater it is not very likely that exposure to anxiety medication is an environmental issue for these populations right now," researcher Gustav Hellström said in a news release. "However, given the low dose used in the study we cannot rule out that, with increasing human population and medical use, this might become a problem in the near future."

The new research was published in the journal Nature Communications.