According to a recent study, a species of aquarium fish has been found to have a surprisingly long memory as it can recall the location of a tasty morsel of food even after 12 days of encountering it. The extended memory may provide the fish an evolutionary edge at the time of scarcity of food, according to the researchers.

In the hierarchy of intelligent animals, fish are placed below chimpanzees, rats and dolphins but above cockroaches. The popular notion is that fish have a memory which ranges from 3 seconds to 30 seconds.

Particularly, African cichlids (Labidochromis caeruleus) tend to show aggression which normally requires longer term memory to remember grievances of the past. In addition, past studies have also shown that cichlids use logic like humans.

Scientists trained African cichlids to enter a zone of an aquarium and receive a reward of food. After 20-minute training sessions for three days, the fish were left for 12 days.

Afterwards, the fish were allowed to roam in the area again as motion-capture software recorded their swimming paths.

The cichlids lingered mostly in the area where they had earlier found food because they remembered their food and were seeking them.

In addition to this, the fish also abandoned their preference for that zone when the scientists trained them to link a different stimulus with food which suggested that they were hanging out there in a hope to find food.

The researchers said that the findings suggest that fish possess the ability to form longer-term associations and memories which could help them in tasks of higher level.

For fish which live in the wild, this ability to associate locations with food could prove to be very vital for survival. "Fish that remember where food is located have an evolutionary advantage over those that do not", said lead scientist Dr Trevor Hamilton.