Do Fish Remember Being Caught?

Is it possible that if you catch a fish early in its life that you won’t ever get the chance to catch it once it has matured? Is it true that individual fish have favorite baits that change over their lifespan?

While there isn’t any way to be completely sure, there’s an abundance of evidence that suggests at least some fish probably do remember being caught. However, it’s unclear whether they can change their behavior to avoid getting caught in the future.

Credit Jonathunder CC BY-SA 3.0

What We Know About Fish Learning And Memory

Fish memory has been much-maligned, but it turns out that they do have both short and long-term memories.

The Reebs Experiments Showed That Fish Can Remember For Years

One researcher, Stephan Reebs, conducted a handful of experiments pertaining to fish learning and memory and in 2008 compiled a report for the University of Moncton in Canada (How Fish Behave).

The report summarized Reebs’ findings and contrasted them with a handful of other scientific investigations on the topic.

Reebs was able to train a group of pond catfish to respond to his call, and the fish remembered the sound of his voice for at least three months after the initial training. Of course, the fact that the researcher fed the fish each time he tried to train them probably had something to do with their willingness to respond.

Then, after a long delay of five years, the researcher returned to the pond and attempted to hail his fish to see if they still remembered the call. More than a dozen of the original group of 19 fish approached the researcher and solicited him for food pellets — a shocking demonstration of long-term fish memory.

Importantly, some fish who did not initially answer the call at first ended up responding after the first day that the researcher returned. So, it seems as though fish can have memories that weaken over time, but which can be refreshed with a review.

Other Research on Fish Memory

Follow-up experiments in a controlled environment with rainbow trout confirmed that fish memory is more formidable than many claim. Trouts were taught to bump their nose against a colored lever, at which point food pellets would be dispensed in their tank.

When the colored lever was removed from their tank and then replaced three months later, the trout immediately returned to bumping against the lever in hopes of getting food.

In another experiment with carp, the same researcher found that carps that had been hooked on a line appeared to avoid hooks inside their tank more than a year after the initial hooking, even when there was bait on the line.

Finally, fish can learn to avoid certain predators by watching other fish fall victim to those predators or by watching other fish intelligently avoid the predators. It’s unclear whether this applies to hooks, but it might.

The Case Against Fish Memory

Not all investigations into fish memory support the conclusion that fish will remember being caught, however.

When an experiment attempted to teach rainbow trout to eat a different type of food than their typical food pellets, the trouts seemed to forget that the alternate food was even edible after they hadn’t seen it for a few months.

Similarly, common targets for fishers, like sticklebacks, seem to forget both positive and negative experiences within a few weeks.

Fish memory also appears to be segregated across the senses in many fish. This means that fish like salmon can recognize areas or objects by smell even when they haven’t perceived it in a long time, but they can’t always recognize things by sight, even if they know the smell.

Likewise, fish don’t seem to have a good memory for landmarks. While they can navigate with a plethora of different systems, there’s no evidence that they know to avoid areas based on experiences they had there.

In other words, fish can probably recognize your boat in the water, but they probably can’t form the association between seeing your boat and getting hooked on your line. Instead, they can only see the line and react accordingly, assuming they were hooked once before.

Even when fish remember something negative, they don’t always act on the information. Tiny cleaner wrasses eat the parasites from gills of common oceanic fish, but sometimes they go too far and take a bite out of the larger fish.

If other fishes see that one of the wrasse’s customers has had a bad experience, they sometimes go away to get their parasites removed elsewhere, but not always.

Furthermore, if the larger fish do have a bad experience with a cleaner wrasse, they don’t swear off cleaner wrasses altogether, only the specific individual that bit them. This suggests that fish might avoid one specific type of hook, but not others that look similar.

How To Potentially Avoid Training A Fish To Avoid The Bait

Given the above information, it’s clear that fish probably remember being caught for at least a few weeks, even if they don’t know how to use their memory to avoid getting caught in the future.

This means that when you catch a fish that is too small to take home, you’ll be training that fish to avoid hooks, potentially for its entire life. However, there might be a way to mitigate the negative memory formed after hooking a fish by feeding the fish with a piece of bait.

By diluting the negative memory of being hooked with the positive memory of getting a tasty meal right after, you could be helping out a future fisher.

On the other hand, if you fish in the same waters more than once, you might want to switch out your baits so that fish who witness you catching their friends won’t be able to figure out what’s going on when you return.

There are still quite a few questions to be answered about fish memory, however.

Between uncertainty surrounding their lack of ability to make behavioral changes based on their memories and dramatically different memory capabilities across species of fish, it’s entirely plausible that some fish might forget their encounter with your hook within a few days.