Why catching and releasing is difficult for fish | MNN

There is a longstanding debate about whether releasing fishing is humane. Anglers say it's a harmless way to play this sport while preserving species at risk. Animal rights activists retort that it is cruel, citing more and more evidence that fish are feeling pain.

A hook pierces the mouth of a fish when it comes in and again when it is removed. Yes, the fish is returned to the water, but does its health have a cost?

New research says yes.

According to a study published by an international team of scientists in the Journal of Experimental Biology, mouth wounds caused by hooks can affect the ability of the fish to feed properly.

When a hook is removed from the mouth of a fish, it leaves an extra hole. Researchers have found that this wound can interfere with the sucking mechanism used by fish such as bass, salmon and trout for food.

"The suction feeding system is a bit similar to the way we drink liquid with a straw," said Tim Higham, co-author of the study, from the University of California Riverside in a statement. "If you make a hole in the side of your straw, it will not work properly."

Hunger during healing

Fish such as trout feed by creating suction with the mouth. (Photo: Dan Bagur / Shutterstock)

For the study, researchers investigated 20 perch – 10 hook and line and 10 netting. The fish were immediately transported to a laboratory where they were monitored and photographed while they were fed. They were all eager to eat, but those caught had difficulty in doing so.

"As we predicted, fish with mouth sores exhibited a reduction in speed at which they were able to attract prey into their mouths," Higham said. "That was the case even though we used barbless hooks, which are less damaging than barbed hooks."

The fish were released safely after the experiment.

The researchers said they did not know how much of this feeding problem would affect the fish's ability to survive in the wild. However, they believe that hook injuries could affect the fish's ability to feed while its mouth heals.

Higham said, "This study highlights that catching up is not as easy as removing the hook and that everything is fine, but rather it is a complex process that should be studied in more detail."

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Why catching and releasing is difficult for fish

Researchers are examining the impact of capture and release on the fish diet once the hook is removed.