Any angler will tell you that freshly-caught fish taste better than ones you find in the store, and many more would add that fish destined for your dinner plate should be killed quickly. That’s not only because it is the ethical thing to do, but because it also helps preserve the flavor. As it turns out, this bit of fishing wisdom has its basis in fact, and scientists in Italy and Spain recently confirmed that killing fish quickly and humanely will lead to better-tasting and longer-lasting fillets.

In a study published in the journal Food Chemistry, researchers determined that how rainbow trout is killed can determine their flavor and length of shelf-life. The researchers experimented with two groups of farm-raised trout. One group was killed with blows to the head while the other died from air asphyxiation, a common method of slaughter still used by many fish farms where trout are left in open air until they die. Asphyxiation is often considered an inhumane method of killing fish.

Researchers then observed the breakdown of chemicals in the two groups, including omega-3 fatty acids. The breakdown of fatty acids produced byproducts that sped up rancidity and worsened flavor. Scientists recorded the start of the deterioration process in the asphyxiated group after just 75 days in a freezer.

“Asphyxiated fillets showed a slight rancid off-flavor by the 105th day of frozen storage and significant rancidity by the 135th day. Instead, a slight rancid odor was not detected for the whole storage period in the fillets from the percussion group,” stated the study.

The researchers decided not to subject anyone to the unsavory aspect of actually tasting the fish, but four specialists were brought in to gauge the “fishiness” of the trout. Chemical tests were also run on the fish, but all it required was a nose to tell that the asphyxiated group was already putrid by the end of the study. Scientists attributed the rapid decay to stress during the slaughter process.

The study only confirms what anglers have already known for many years. Ethical fishermen prefer percussive stunning, spiking, or any other method that kills the fish instantly. Methods that kill fish slowly are sometimes tempting because they do not require active participation but may cause suffering to the fish.

Image from Ralph Daily on the Wikimedia Commons

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