From SOTT:

Farmed Atlantic salmon often suffer from such high levels of stress and depression that many become lethargic and essentially give up on life, finds new research.

Many farm-raised salmon exhibit behaviors and brain chemistry nearly identical to those of very stressed and depressed people, according to a new study with implications for animal welfare and treatment of mental illness in humans.

The research, published in the journal Royal Society Open Science, could help to explain why so many fish farms have “drop out” or “loser fish” that have stunted growth and listlessly float at the surface of tanks, seemingly wanting to die.

“I would not go so far as to say they are committing suicide, but physiologically speaking, they are on the edge of what they can tolerate, and since they remain in this environment, they end up dying because of their condition,” lead author Marco Vindas, of the University of Gothenburg, told Discovery News.

Vindas and his team made the determinations after studying both healthy and growth-stunted fish at a commercial Atlantic salmon farm in the Langenuen Straight of Western Norway. All fish were reared according to production standards, euthanized and then analyzed with a focus on the fish’s brain chemistry and levels of the stress hormone cortisol.

The “drop out/loser” fish were found to have much higher amounts of cortisol in addition to increased activation of what is known as the serotonergic system. This main neural system regulates the neurotransmitter serotonin in the bodies of fish as well as in other animals,…

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