How Catch And Release Can Damage Fish

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If you catch a fish and you eat it, it has no chance of survival. That’s pretty obvious.

If you catch a fish and you set it free, it could be just fine. Indeed, it could be rather fun for the fish. “Hey, did you see that? You wouldn’t believe what I just saw! Hey, you know that eagle that ate Joe last week? I could see where its nest was! And this guy had this whole bucket of leeches! Holy crayfish!”

But most likely, if you catch a fish intending to release it, there is a chance it will not fare so well. People who catch catfish intentionally know this, and don’t bother with catch and release. I’m not sure if I’ve ever caught a catfish where the hook didn’t go deep into its gut as the sole action in the entire process of grabbing the bait. Not even worth taking the hook out. You just take the catfish home, clean it, and get the hook then. Generally, live bait has a higher chance of this sort of thing happening. Unless you are jigging with a fairly large hook and a live bait that is hanging off, the chance of your fish swallowing the hook, even part way, is high. Generally, as well, fishing in this manner is associated with fishing for food or, one might hope once in ten lifetimes, a trophy walleye or something.

I personally fish almost exclusively with lures. If the lure comes with a treble hook, I’ll either remove it and replace it with a single hook, or cut off one or two hooks. I mush or cut off the barbs. I take at least one of the treble hooks off any lure with multiple trebles. For bait hooks, I smush or remove the barb. And so on.

(By the way, this give me the opportunity to put a single weedless hook on a lure that is essentially designed to catch on to every damn thing in the lake, allowing for more options when casting.)

When I catch the fish, since I’m casting and reeling and the hook is barbless, it is pretty easy to remove the hook from the fish. Sometimes, if the fish is fairly big, I don’t actually want to land it. That may involve too much handling, and that can damage the fish. With a single hook and no barb, I can get a look at the fish, and flick it free pretty easily about half the time.

(Also, I carry at least one very large needle nose pliers. I can grab the base of the hook or the hook/lure with that, and with a simple twist, release the fish before or after landing, depending.)

I’m pretty sure that I don’t do a lot of damage to the fish I fish for. If a fish I catch is legal and damaged, I eat it. (Not right there on the spot; I clean and cook it first.)

How might catch and release injure fish that are not particularly mangled by the process? There is a paper just out in the Journal of Experimental Biology, bu Melissa Thompson, Sam Wassenbergh, Sean Rogers, Scott Seamone, and Timothy Higham. In “Angling-induced injuries have a negative impact on suction feeding performance and hydrodynamics in marine shiner perch, Cymatogaster aggregata” the researchers report that injury to the inside of the fish’s mouth can change the pressure gradient that these fish use to suck prey (and lures) into themselves. It is not demonstrated that this impacts survival, but it does seem to impact feeding efficiency.

“The suction feeding system is somewhat similar to how we drink liquid through a straw,” Higham said. “If you poke a hole in the side of your straw it’s not going to work properly.”

Fish researcher Tim Higham explains, “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. This was the case even though we used barbless hooks, which are less damaging than barbed hooks. Although we don’t yet know how/if this reduction in feeding performance would affect fitness and survivability in nature, we can say that fishing-induced injuries impact the fish’s ability to feed while the mouth is healing. 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.”

This is obviously going to depend on the kind of fish in question. As noted above, the whole suck-in-the-food approach for catfish may simply do them in. But I’m not sure a Northern or Muskie is feeding in exactly the same way. Clearly, more research is needed!

The abstract of the paper:

Fishing is a popular and lucrative sport around the world and, in some cases, may contribute to declining fish stocks. To mediate this problem and maintain fish biomass in aquatic ecosystems, catch-and-release fishing, whereby a fish is caught and immediately released, has been implemented in many countries. It is unclear whether the injuries to the mouth that are caused by the hook have an impact on feeding performance of fishes. Using high-speed video and computational fluid dynamics (CFD), we asked whether injuries around the mouth caused by fishing hooks have a negative impact on suction feeding performance (measured as maximum prey velocity) of the commonly angled marine shiner perch (Cymatogaster aggregata). We hypothesized that fish with mouth injuries would exhibit decreased feeding performance compared with controls. Ten shiner perch were caught using scientific angling and 10 were caught using a seine net. Feeding events were then recorded at 500 frames per second using a high-speed camera. Compared with the control group, maximum prey velocity was significantly lower in the injured group (P<0.01). Maximum gape, time to peak gape, maximum jaw protrusion and predator–prey distance were comparable between the control and injured groups, leading us to conclude that the injury-induced hole in the buccal cavity wall reduced the pressure gradient during mouth expansion, thereby reducing the velocity of water entering the fish's mouth. This was confirmed with our CFD modelling. Fishing injuries in nature are likely to depress feeding performance of fish after they have been released, although it is currently unclear whether this has a significant impact on survival.

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11 thoughts on “How Catch And Release Can Damage Fish

  1. An interesting post Greg. This may be of interest:

    Last summer I my kids were jumping off the local jetty and I watched three or four different fishers catch the same distinctive individual undersized bream over about an hour. Each time it became more and more haggard, to the point that I was certain after the last time that it would die soon after.

    Recreational fishing is becoming an ever-more popular and vigorously-promoted past-time in my corner, and there’s a frequent mantra about catch-and-release, as if this negates the increasing pressure on stocks that are already under multiple anthropogenic pressures. I suspect that increasing recapture rates will at come point emerge above the data-noise as an increasing cause of mortality.

    Another thought on fishing: large-size females are disproportionately represented in the breeding stock that recruits to new generations. Having a catch policy that allows any fish over a certain minimum size to be retained has a huge impact on the amount of eggs/fry/juveniles that are produced. There should also be retention exclusions for fish <iover a certain size – letting these fish go will over a range ensure far more recruitment than letting go a juvenile that has yet to attain sexual maturity and/or maximum fecundity, and that may not even reach an age where it can breed productively.

    Finally, to those fishers who think that it’s OK to leave fish and squid asphyxiating on a jetty/boat bottom until they die – you are beyond contemptible. Whilst supervising my children I was forced to watch numerous grounded southern calamari thrashing their arms and flashing their chromophores through an astonishing (and beautiful) range of colours in an attempt to breath. These animals have highly developed neural systems, with huge, complex eyes and a capacity for relatively sophisticated analysis, and it is a damning indictment on those people who are so bereft of ethical standard that they are content to let these animals suffer a moment longer than is absolutely necessary.

    1. “think that it’s OK to leave fish and squid asphyxiating on a jetty/boat bottom until they die – you are beyond contemptible. ”

      Indeed, maybe those who do that should read John Wyndham.

      Also with overfishing look at the explosion in jellyfish populations, read

      e.g. Lisa-ann Gershwin ‘Stung!: On Jellyfish Blooms and the Future of the Ocean’


      Carl Safina ‘Song for the blue ocean’

    2. ” There should also be retention exclusions for fish <iover a certain size "

      This is done for sturgeon in Oregon, at least.

  2. I have to admit I feel the allure (get it?) of fishing — the artistry, the skill, the peaceful communion with the great outdoors. And I love the picture at the top of the post. They are beautiful, and being something of a packrat, I instantly and desperately want to collect them.

    However… these days I’m pretty much of a mind that people should stop bothering the critters. I know. I’m a wet blanket. I’m just saying that maybe humans could put some of their excess energy into addressing invasive species, for instance, or photography, or citizen science, etc.

    Just my 2 cents.

  3. Catch & Release is nothing but another form of animal torture by males, who need an ego boost. I’m not against hunting, you get the food you need for yourselves to survive.
    OK! but to wound & let go is mean & nasty.
    My dad did tell me of a form of Catch & release but it aint popular as it requires great skill, and that is to knot bait onto a string and then catch the fish with just that…NO HOOK!

  4. Well kudos on your ethics here.

    It is a little ironic for me, after watching a number of Youtube videos of predation in the natural world. “Red in tooth and claw” doesn’t even come close to describing the cold-blooded cruelty which most wild critters will suffer at their natural demise at the hands, and claws, and teeth, and fangs, and stingers, and jaws, and talons of their predators.

    Being caught and released, or even becoming a filet on a dinner plate, is a much more gracious way to go than being eaten alive, ot torn to pieces, or eaten from within.

    1. Hmm. Fair enough, I guess. OTOH, being beaten up by the process of being caught only to be released and eaten alive, or torn to pieces, or eaten from within seems a little bit like piling on. Not to mention, as has been noted, the question of what pressure this practice adds overall to fish populations and ecosystems.

      Nobody here said humans didn’t need to eat, even if it’s just Soylent Green, though Bernard J. has pointed out that the process of handling caught fish is not always gracious either.

    2. Nature is indeed red in tooth and claw – as a biologist I see it up close…

      The comparison skirts close to a tu quoque fallacy though, if not landing deep within that territory. As humans we should act in a way that reflects the best of humanity and of human understanding: respect for the world around us not only says something about us, but shapes us going forward.

      There’s also the issue that oa mentioned and that was the subject of my initial link – humans have an extraordinary and overwhelming impact on the biosphere, and if we intend to have a sustainable global ecosystem we need to be ever more vigilant with respect to our behaviours. All of our behaviours, no matter how insignificant they might be. Ecological pressures might be subtle but they can be profound, especially over unperceived time and through unperceived space/connections. Evolution and ecosystem balances respond to the merest wisps of survival-influencing pressure…

    3. As an aside, “cruelty” is a value-laden judgement. Whilst humans are animals, our sophisticated abilities to analyse and to be self aware/ethical mean that our actions are layered with additional understandings that cannot also be unconditionally ascribed to non-human taxa.

    4. “our sophisticated abilities to analyse and to be self aware/ethical mean that our actions are layered with additional understandings ”

      Agreed. But our ethics does have limits. Most people do not hold themselves to the ethic of certain Buddhists, for example, who would not use an automobile because it would mean squashing insects on the windshield.

      And most people would accept a certain amount of suffering to themselves as the consequence of simply being alive. We eat animals and most consider it ethical, and there is some validity to the notion that sportfishing, even with barbed hooks, is still within the realm of ethical behavior. I am not sure where a bright line can be drawn.

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