Fish Personality Tests Could Be the Key To Improving Seafood Farming

Knowing a bit of fish psychology might be the key to the future success and health of global aquaculture.

Researchers at the University of Stirling and the Institute for Food and Agricultural Research and Technology (IRTA) in Catalonia have published a new study on fish behaviour that aims to help farmers increase yield, by gauging how fish will adapt to life in captivity.

The first caveat, however, is that all fish—from bear-dodging salmon, to bottom-feeders like catfish—have their own behavioural predilections. In this case, researchers used Senagalese sole, a popular farmed fish throughout Europe that, according to study co-author Dr. Sonia Rey Planellas, is suffering from a decline in reproduction in farmed environments.

The researchers developed a series of tests aimed at determining the sole's Stress Coping Style (SCS)—the manner in which the fish react to stress-inducing situations. The sole were subjected to an operational behavioural screening test (OBST) to determine a dominant personality trait.

Broadly, there are two types of personalities found in sole: reactive and proactive (although Planellas admits there can be some middle ground).

"Reactive fish are shy, non-aggressive individuals with a more exploratory behaviour and higher levels of cortisol under stressful conditions," she says.

"Whereas proactive fish are mainly bold, more dominant and usually aggressive individuals that display more routine like behavioural patterns and that have lower levels of cortisol under stressful conditions."

The three primary tests, which, undeniably, some readers may find disturbing (but what does this say about being raised on a fish farm?), included "restraining"—in which a fish was held in a net under water and then out of water; "new environment"—the fish being placed in an unfamiliar tank; and "confinement"—finally, being placed individually in a plastic tank separate from any others.

Researchers then measured blood chemistry markers to indicate stress levels.

"Cortisol, glucose and lactate blood levels, which are reliable markers of stress in humans, were observed to fluctuate in the same way in fish, being higher in reactive fish than in proactive fish submitted to stressful situations," says Dr. Zohar Ibarra-Zatarain, of the Centro de Innovación Tecnológica in Mexico.

Utilising selective breeding to encourage these personality types could prove incredibly beneficial to farmed fishing environments, because some fish are simply better suited to living in a confined environment. Planellas and Ibarra-Zatarain believe that their work will make for a practical and cheap method for farmers to increase the health and reproductivity of their fish:

"The objective of this work was precisely to establish OBST, which could be implemented by farmers without specific skills or experience," says Ibarra-Zatarain.

This new research become an essential part of improving an industry that is often contentious.

Farmed fishing, a practice opposite that of "wild-caught" fishing, tends to get a bad rap. Living conditions in farmed environments have been notoriously filthy, with disease, sea lice, and ensuing antibiotic use, sometimes running rampant.

However, both farmed and wild fishing have raised serious ethical, ecological, and health concerns for people around the world.

As populations have boomed and the demand for fish has continued to grow, overfishing has become a serious concern. The World Wildlife Federation published some scary statistics on the matter, the most damning of which is this: "Unless the current situation improves, stocks of all species currently fished for food are predicted to collapse by 2048."

More recently, overfishing has even been linked to climate change, due to its trickle-down effects throughout the marine ecosystem. Most fish that humans eat are predatory, consuming the smaller fish and marine life of the ocean; as these fish are killed off, breeding of smaller fish varieties accelerates, as does carbon emissions.

"Removal of predators is likely to lead to an increase in ocean ecosystems' CO2 production, and ultimately that fishing and shark finning are contributing to climate change," Salon reported recently.

With these serious issues arising from overfishing, there is no doubt that aquaculture must play an even bigger role in the years to come. If that means that fish psychology is the next weapon to fight global warming, then so be it.