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.