It's long been believed that fish have a paltry memory span of only 30 seconds. But a team of Canadian scientists conducted a study on African Cichlids, a popular aquarium fish, and found their memory can actually last up to twelve days, after administering a 'food reward' experiment.
There are hundreds of species of African Cichlids that can be found in the lakes of Eastern Africa, with thousands more species developing. In Lake Malawi - an African Great Lake located between Malawi, Mozambique, and Tanzania - there are 850 different species of cichlid with all but two of them being endemic to the waters. Because of the variety in species, colors, and patterns, they have become a well-known and prized aquarium fish.
In the study, the researchers noted that the cichlids exhibited many complex behaviors, such as aggression, leading them to believe that these fish could be capable of possessing a strong memory. They then began a three-day training session where each cichlid was directed to enter a particular zone of the aquarium in order to receive a 'food reward.' After the training session the fish were given twelve days off and were then reintroduced to their training area as their movements were recorded with motion-tracking software.
Not only did the fish recall their zone where they received the food reward by exhibiting a preference in the specific area, but they also were capable of reversing this preference after they were instructed to associate with a new area. This ultimately proved the cichlids - and possibly other fish - are capable of advanced memory tasks.
"Fish that remember where food is located have an evolutionary advantage over those that do not" said lead scientist Dr. Trevor Hamilton, in this EurekAlert! news release. "If they are able to remember that a certain area contains food without the threat of a predator, they will be able to go back to that area. Decreases in the availability of food would promote the survival of species that can remember the location of food sources."
Additionally, the cichlids were found to spend more time near the "up" end of the tank rather than the "down" end because they remembered that was where their food pellets were dropped from.
The researchers presented their findings at the Society for Experimental Biology's annual meeting. It has yet to be published. However, because of the success of this study, the researchers are now exploring whether environmental conditions and drugs can affect a fish's memory.
You can read more about the study in this BBC Nature article.
