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Ever released a fish back in the water to only get a bite 5 minutes later and thought to yourself "did I just hook the same fish?" I mean fish are not known to have the greatest memory out there ... but is that really true? In the past decade or so there has been a significant effort to research and test the memory capabilities of fish. Studies have shown that a fish's memory can last from a few days to even years. A fish's long term memory is directly related to their ability to associate events with food. It is believed that the reason for a fish to have a long term memory that is so closely tied to food availability provides an evolutionary advantage. If a fish can recognize that a certain location has no food will prevent the fish from going there. The opposite is also true, if a fish can recognize that a location has an abundance of food then it will keep coming back. WAIT!!! If fish are able can remember up to a few years then why are fish still being caught? Should the fish learn what a fishing lure looks or a hook and associate it as being bad? In order to understand that we need to look a bit closer to the research that was conducted. Fish Can Be Trained To Remember There are multiple studies that took a look at a fish's ability to remember certain associations relating to food under a controlled lab setting. In one study, multiple feed tubes were given to the fish but only one of the coloured tubes had food. Over time the fish learned which colour had food and only went to that tube to feed. The researchers then reduced the frequency that fed the fish from the tubes. Even after a few months once the coloured tubes were presented the fish went to the colour tube with the food. Here is an interesting article that was written by a professor in the University of Moncton Quebec Canada that talks about how he received a message from American professor where he outlines how he trained a pond of catfish to response to a calling "fish-fish" before feeding. I personally thought this was a very interesting read. Another study using African Cichlids, a popular aquarium fish, subject the fish to a 20-minute exercise for 3 days where the fish needs to enter a particular zone for food in a multi-compartment tank. The fish were then given a 12-day break outside of the tank before they were reintroduced back into the multi-compartment tank. Once the fish was back in the multi-compartment tank they were observed to be more efficient and sure of themselves how to get to the correct compartment where the food was. This article refers to a study investigating how captive young fish can be trained to associate sound at a certain location for feeding and how fish farmers can use this to call their fish in a lake for feeding. This could potentially mean that fish farmers don't have to use cages to keep fish in resulting in healthier farmed fish. These studies were conducted under controlled conditions where someone had the ability to train the fish to react to a certain event that is associated with food. At this point these studies have just confirmed that fish have the ability to remember events but how does this relate to wild fish? Well, this study investigated if Carp were able to remember being caught and released. Fish were placed in a drainable pond and tagged. After 100 hours of fishing the probability to catch another fish within a designated area dramatically decreased. Additionally the ability to recapture the same Carp after being caught once decreased significantly ... way more than what was expected. This showed that Carp has the ability to recall and learn from their experiences. The above study also looked at what happened if a Carp that was caught did not return. Well, the study found that the general population became harder to catch. This would suggest the fish were able to conclude that fish not returning must mean danger and reduce their activities for safety. A Salmon's Memory Great Example The most famous example's showing how a fish can recognize patterns long term would be Salmon during spawning season. Salmon are born in a freshwater lake and will live their younger years within rivers until they are large enough to head out to the ocean where they will continue to grow. It will be years until the fish will be able to start spawning. Once Salmon is ready to spawn, they head out to the same lake that they were born in. Travelling through countless rivers they are able to locate the correct lake through memory and smell. What Does This Mean For Fish In The Wild The above examples demonstrate that fish has the ability to remember events and in the case with the study with the Carp even associate danger with missing fish. After reading the studies myself I am left scratching my head thinking ... Why does the same fish sometimes get caught again quickly after I release it if they are able to remember things? The only reasoning I was able to come up with is that fish are like bad students .... generally speaking of course. By that, I mean it seems to take a while before a fish can pick up on a pattern like a certain lure may be a danger or recognize what a hook looks like. However, this might explain why the much larger fish are harder to catch. They might have recognized things like a hook or certain type of baits and how they move underwater might be bad. This is also why bait presentation is important to hide recognizable features. It is reasonable to believe that fish may not necessarily remember being caught and released in the short term but in the long term, a fish can learn a pattern that would be associated to danger, such as the sound of a boat, certain styles of bait presentation, etc. The larger and older fish has probably experienced and seen more things to learn from which could contribute to why they are hard to catch.

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