Catch and Release Fishing Might Hurt Fish More Than Thought

By Anna Groves | October 9, 2018 2:57 pm
(Credit: kolikovv/Shutterstock)

(Credit: kolikovv/Shutterstock)

If you’re a fish, it sucks to have a hole ripped in your mouth by a hook.

Actually, researchers found, it sucks less.

New research out today in the Journal of Experimental Biology found that fish can’t suck up food as well after having a hole poked in their mouth by a fishing hook.

The team, led by Tim Higham at UC-Riverside, focused on marine shiner perch for their study. These perch are a common target for anglers and belong to a broader group of fish (along with bass, bluegill, and other perch) known as suction feeders.

These fish eat by getting close to – but not quite touching – their next bite of food. Once in place, they open their mouth extremely fast and the pressure difference pulls in a mouthful of water and food.

This is the same way humans suck. Imagine yourself drinking through a straw: all you’re doing is opening your mouth while keeping your lips sealed tight around the straw.

Now imagine there’s a hole poked in the side of the straw. Or, to be slightly more gruesome, in the side of your mouth. The suction wouldn’t work as well. This, the researchers found, is analogous to what happens to a fish after an encounter with a hook.

Sucks to Not Suck

The researchers caught the perch for their experiment off Vancouver Island in Canada. Half they caught with a traditional hook-and-line. The other half they caught in a seine net to serve as a hole-less control group.

They brought the perch back to land to undergo tests in tanks in their lab at the Bamfield Marine Science Center.

While watching with high-speed video cameras, they fed the fish. The videos allowed them to measure how wide the fish opened their mouths and how quickly, how close they got to their bites of food, and how fast the food was sucked into their mouths.

They found that the angled fish behaved the same as the net-caught fish. They opened their mouths the same amount, just as quickly, and approached their food at the same distance.

But thanks to the hole ripped in their mouths, the recently-angled fish sucked up food 34 percent slower than the net-caught fish.

“We were surprised with how dramatic the difference was,” says Higham. “For there to be that large of a difference was definitely striking. No pun intended, of course.”

Much to Learn about Fish

The researchers also used computer modeling to predict how quickly the food should get sucked up, based on parameters like the volume of the fish’s mouth and the size of the hole ripped open by a hook.

Their models predicted the hook-hole would slow their eating, but less than half as much as they actually observed. In other words, the fish were even worse at eating than expected. This suggests something else is at play that is not yet understood.

Important next steps will be to also find out how quickly the hook-induced holes heal in the fish, and whether the slowed eating makes a meaningful difference in their health.

Better Hooks for Better Fishing?

Though the unknowns make it too early to suggest any changes to fishing practices, Higham emphasizes that current catch-and-release practices are still certainly better for fish populations than not releasing the fish at all.

If future research were to reveal that this slowed feeding really impacts the fish, one possible solution could be to simply reduce hook sizes whenever possible. This meshes with the findings from the group’s computer models: larger holes mean worse performance during feeding.

Another application could be to reconsider catch-and-release fishing of rare fish, depending on how well the released fish are surviving.

But it’s all too soon to say. What we do know, now, is that a hook injury affects how fast a suction-feeder can suck in prey.

“All we were doing was what people normally do in capturing (fish) using hook-and-line fishing,” says Higham. “It’s a fairly simple question. There’s nothing complicated about it, it’s just no one has ever thought of this or looked at it in this way.”

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  • Peterc34000

    Hey, I have an idea! Leave the damn fish ALONE…

    • Jon d David

      Nope! Get the oil hot!

  • Itsallbs

    A hole in the mouth beats the other option for the fish. If we kept them all we would be out of fish fairly quickly.

  • Dave

    Bottom line , if you catch em, eat em , it’s more humane …. and not to mention , tasty!

  • Jon d David

    What an absolutely amazing waste of time and resources in this study! Donated/grant money goes to brainwashed liberal graduates to study a fish? Guess that the trust fund babies need to stick together and study other bottom feeders to justify a 4 year ‘degree’… Why aren’t you actually contributing to ANYTHING to society? Go find a safe space and quit wasting everyone’s else’s time!

    • nice_trousers

      I’m an avid bass fisherman, and you sir are an idiot

      • Jon d David

        What’s wrong -can’t catch a walleye?
        Better take a look in the mirror ‘avid green carp fisherman’…because that was an ignorant comment that nobody cares about.

        • nice_trousers

          lol I caught my personal best walleye last month, 7 lbs

          • Jon d David

            That’s great- even for LoW where I fish!
            Now, I’m assuming you released it? And according to this study….it’s probably going to starve to death because it can’t eat?

          • nice_trousers

            I did release it, because on my lake Walleyes are somewhat rare. I could have kept it, but I catch enough other fish otherwise so I didn’t need to.

            do you not think about that things?

          • Jon d David

            Think about what ‘things’?

            I released more walleyes in the last year on LoW than 99% of people catch in 10 years… According to this worthless waste of time/money article; those fish are not going to be able to eat…

            And since most people release bass…that means that according to this stupid article-those bass are going to just die too.Did you consider those ‘things’?

            So, did you actually read the article or are you acting ignorant just to see if you can get a rise out of someone? Calling someone an idiot as your opening line is one of the clearest indications of being one…. These forums are a joke- if you said anything like your opening line to my face….you would learn never to do that to anyone again-and that’s why this generation is a bunch of whiny babies.

          • Jon d David

            I’m assuming anyone who refers to themselves as bass fishermen and ESPECIALLY musky fishermen…they see right through this supposed ‘study’… Catch and release is clearly great for a fishery.
            With the exception of crappies from deep water-very poor survival rates…really, all fish from over 30’ should be at minimum; looked at closely. With the exception of trout (no air bladder problems).
            Saying that a fish can’t eat after being caught is absolutely ridiculous. Even if they justify it by saying suction feeders- a sturgeon will survive repeatedly being caught…so where are we at? Suckers, buffalo, carp? Large mouth bass are essentially suction feeders- and have ZERO issues surviving being caught and released. …
            Hopefully I’m not coming off as belligerent- but if I am, keep in mind that these are the same people who have destroyed Mille Lacs with false data and improbable information collection.
            Don’t buy into these theories!

  • Name

    If you needed any more proof that scientists are super smart; a group of them collected salary to go fishing!

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