Scientists Expand Fish Memory From 3 Seconds to Several Months

Published on January 18th, 2010 | by

Fish are often considered lesser beings. In fact, pesce vegetarians justify eating fish because they don’t consider them to feel pain and suffering, and they think it is better for their health.  New research challenges prior assumptions about fish, including their memory.  The long standing myth that fish can only recall something for three seconds has been disproved.

Photo by Mike JohnstonFish memories are better than previously assumed.
Fish memories are better than previously assumed.

Researchers at Charles Sturt University call the idea that fish have extremely short memories “absolute rubbish”.  Dr Kevin Warburton explains:

There’s been a lot of work done over the last 15 years on learning and memory in fish and it as been found that fish are quite sophisticated. Fish can remember prey types for months; they can learn to avoid predators after being attacked once and they retain this memory for several months; and carp that have been caught by fishers avoid hooks for at least a year. That fish have only a three second memory is just rubbish.

What came out, unexpectedly, was that while they were learning about their prey, their foraging efficiency went down.  With one type of prey, the fish got more and more efficient at catching their food, but when we put two different types of prey in together, their overall efficiency dropped. We think it was because of they suffered from divided attention. It’s a cost of learning.

Given the evidence discovered by Dr. Warburton, it appears fish may have episodic memory, the ability to remember a specific event from the past, something once assumed to be only a human trait.   If fish remember to avoid predators after just one attack, the avoidance is more than just a conditioned response.  Wikipedia defines episodic memory “as being a “one-shot” learning mechanism. You only need one exposure to an episode to remember it.”  Scrub jays, chimpanzees, and gorillas have been shown to have greater memories than previously assumed.  Now, it is freshwater fish’s turn.  As anthropologist Charles Menzel explains, “Animals are using something related to episodic memory, but not necessarily the same as in humans.  Animal memory systems have always been underestimated—the upper limits are not really known.”

Does a longer memory make catching and eating fish less humane?  Does it signify fish are higher beings than previously assumed?  Whatever the personal significance for pesce vegetarians, the Australian research expands our understanding of fish.


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