Animals Wildlife Why Catch and Release Is Tough on Fish By Mary Jo DiLonardo Mary Jo DiLonardo LinkedIn Twitter Senior Writer University of Cincinnati Mary Jo DiLonardo has worked in print, online, and broadcast journalism for 25 years and covers nature, health, science, and animals. Learn about our editorial process Updated October 10, 2018 Share Twitter Pinterest Email Enjoyable for everyone ... except for the fish. Iakov Filimonov/Shutterstock Animals Wildlife Pets Animal Rights Endangered Species There's a long-standing debate about whether catch and release fishing is humane. Anglers say it's a harmless way to enjoy the sport while still conserving at-risk species. Animal rights activists counter that it's cruel, citing mounting evidence that fish feel pain. A hook pierces a fish's mouth when it goes in and again as it's taken back out. Yes, the fish is released, but is there a cost to its health? New research says yes. Mouth injuries caused by the hook can harm the fish's ability to eat properly, according to a study published by an international team of scientists in the Journal of Experimental Biology. When a hook is removed from a fish's mouth, it leaves an extra hole. Researchers found that this wound can interfere with the suction mechanism used by fish like bass, salmon and trout to feed "The suction feeding system is somewhat similar to how we drink liquid through a straw," study co-author Tim Higham of the University of California Riverside said in a statement. "If you poke a hole in the side of your straw, it's not going to work properly." Hungry while healing Fish like trout feed by creating suction with their mouths. Dan Bagur/Shutterstock For the study, the researchers studied 20 shiner perch — 10 caught by hook and line and 10 caught by net. The fish were immediately transported to a lab where they were monitored and photographed while they were fed. They were all eager to eat, but the ones caught by hook had significant difficulties doing so. "As we predicted, the fish with the mouth injuries exhibited a reduction in the speed at which they were able to draw prey into their mouths," Higham said. "This was the case even though we used barbless hooks, which are less damaging than barbed hooks." The fish were safely released after the experiment. The researchers said they don't know how much this feeding issue would affect the fish's ability to survive in nature. However, they believe the injuries caused by the hook would affect the fish's ability to feed while the mouth is healing. Said Higham, "This study emphasizes that catch-and-release is not as simple as removing the hook and all being well, but rather is a complex process that should be studied in more detail."