Fish are like people when it comes to suffering from stress, and they respond the same way humans do: By releasing extra quantities of the steroid cortisol into their bloodstreams, two Oregon State University researchers say.
Professors Steve Kaattari and Carl Schreck found that young salmon raised in hatcheries are subjected to a variety of stresses that can lead to poor health and disease. Among the sources of stress are their overcrowded living conditions and the frequency with which they are netted, handled and removed from the pond to have their fins clipped.
"Increased levels of cortisol in the blood suppress the immune system, leaving the animal more vulnerable to diseases," Schreck said.
Why salmon, and humans, respond to stress with a mechanism that makes them more vulnerable to disease is "a good question," he said.