Innovative Behaviour in Fish: Atlantic Cod Can Learn to Use an External Tag to Manipulate a Self-Feeder
This report describes an unexpected innovation by three Atlantic cod during a Swedish experiment to determine which members of a group of fishes would bite a release lever to produce food. The three fish (from two different experimental groups) got an identifying bead that was attached to their top fin caught on the release line for the food. Over time, they stopped reacting as if threatened and refined their technique. By the end of the experiment, they were able to access the food much more quickly using the bead method, and preferred it to the biting technique.
[Abstract excerpted from original source.]
“This study describes how three individual fish, Atlantic cod (Gadus morhua L.), developed a novel behaviour and learnt to use a dorsally attached external tag to activate a self-feeder. This behaviour was repeated up to several hundred times, and over time these fish fine-tuned the behaviour and made a series of goal-directed coordinated movements needed to attach the feeder’s pull string to the tag and stretch the string until the feeder was activated. These observations demonstrate a capacity in cod to develop a novel behaviour utilizing an attached tag as a tool to achieve a goal. This may be seen as one of the very few observed examples of innovation and tool use in fish.”