Technion researchers have presented a study showing that contrary to what was previously believed, fish can remember stimuli for between four and five months. Previous studies into fish memory led to the conclusion that fish can remember for only three seconds.
Researchers Boaz Tzion, Assaf Barki and Ilan Karplus presented the study. The three said the new findings could be used to develop environmentally friendly methods of fish farming based on conditioned reflexes.
Currently, many fish farmers use cages submerged in lakes or oceans to raise their fish. The cages are expensive to build and maintain, and ecologists say the fish's nitrogenous secretions can damage the environment. In some areas, the farming method has been outlawed.
Instead of using cages, farmers could train fish to associate a certain acoustic noise with food, researchers said. Fish would be trained to recognize the sound over the course of a month, and then released into a large open space in a natural body of water. Farmers would continue to sound the noise once a month to keep the fish accustomed to returning for food when they hear the sound. When the time came to harvest the fish, farmers could send out the sound and catch the fish as they gather.
The use of acoustics would allow fish to roam over a volume of water much larger than that in the average cage, Tzion, Barki and Karplus said, and would greatly reduce environmental impact. The method would also reduce the cost of fish feed, as fish would find most of their own food in their natural habitat.
The research was presented at an annual conference on agricultural engineering. Approximately 30 other studies were presented as well, as were dozens of posters summarizing research conducted by students in various Israeli universities.