While I've yet to convert to full-blown vegetarianism, I try to remain conscious of my meat-eating choices. I've done my share of researching the conditions of local farms, but I never really gave much pause to fish farm conditions — at least until now.
In a new study published in Royal Society Open Science, Swedish marine biologist Marco Vindas examined the brains of so-called "drop-out" fish. These are the fish that simply zone out and float to the surface in the often-crowded, stressful world of an aquaculture tank. If this were a horror movie, we'd be talking about the overstimulated teen who simply sits down in the hallway and waits dumbly for the slasher while everyone else runs away. They simply give up and phase out.
Vindas found high levels of the stress-response hormone cortisol in drop-out salmon at a commercial aquaculture facility. Their serotonergic systems, which regulate cortisol, showed the same sort of sustained activation that produces depression-like states in several animal species.
So yes, as uncomfortable as it sounds, your farm-raised frozen fish sticks might have come from tanks of infinite sadness, where unnatural and overcrowded conditions frequently can produce severely depressed fish.
Fish farmers aren't crazy about the situation either, as "drop-out" fish are typically undersized, malnourished specimens that cut into overall profitability. The Swedish study doesn't make any hard and fast recommendations, but it does mention the possibility of identifying stress-coping genetic markers in fish species and selectively breeding to encourage them.
Marine biologist Vindas also proposes that this sort of serotonin-mediated behavioral inhibition may have evolved in vertebrates to minimize stress exposure in vulnerable individuals, thus informing the human potential to freeze up and become unresponsively depressed in the presence of extreme stress.
These findings, and future studies, might even help produce better treatments and preventions for "human stress-based pathologies." In the meantime, however, the study does wonders toward making us second-guess farm-raised salmon.