Catch and release fishing isn’t as harmless as many people think.
Researchers at the University of California, Riverside, the University of Alberta, the University of Calgary, and the University of Antwerp found that removing the hook from a fish’s mouth after it’s been caught can limit their ability to catch food. Published in the Journal of Experimental Biology on Tuesday, the study showed that fish that use suction feeding can’t suck their food in properly and experience a 35 percent reduction in feeding ability.
“What we wanted to do was try to figure out what the impact on the fish might be when it is caught using a hook and released,” Timothy Higham, a professor of biology at the University of California, Riverside, and author on the paper, told Newsweek. “I’ve done a lot of research looking at how fish feed and multiple authors on the paper are avid anglers, so it was a natural experiment and surprisingly had never been done.”
Suction feeding is a common style of feeding for many recreational sport fish species, like bass, salmon and trout. These fish suck in prey by rapidly expanding their mouths. This motion causes negative pressure their mouths compared to the water they’re in and the pressure gradient from that process then pulls the prey into the fish’s mouth. It’s similar to how we drink through a straw, and if there’s a hole in the straw we won’t be able to get the liquid up.
“We caught one group of fishing using an actual hook and line, so we did it just as an angler would, and then we caught another group of fish with just a net, so they had no mouth injury, but they were caught. It’s important to keep that standardized,” Higham said. The team caught only marine shiner perches, which are common catch-and-release fish. They tested 10 fish with the mouth injury and 10 without the injury in their lab to see how quickly and how much they were able to feed.
“We thought there’d be an impact, but the impact size we used was fairly small in diameter so we weren’t sure we’d pick up a significant effect,” Higham said. “When we saw a 35 percent in the ability to feed we were quite surprised. That was much more than we thought would happen.”
The decrease in feeding ability could cause issues for fish populations but more research is needed to see the impact on that scale. “When people are fishing, they have a choice in regard to what size of the hook they use, and I think if you really emphasize using the smallest hook diameter necessary, that would potentially be very helpful,” Higham explained. However, he doesn’t advocate that people stop fishing. “Maybe this will help encourage people to think a little bit more about the damage their causing.”