In Finding Nemo, Dory, the goofy, lovable Blue Tang (Paracanthurus hepatus) voiced by Ellen DeGeneres, adds comic relief with her short-term memory loss and, eventually, saves the day by remembering a very important address (“P. Sherman. 42 Wallaby Way. Sydney!”). Finding Dory picks up on this plot line when Dory remembers her prior life and goes on a quest to find her parents. While this movie and its predecessor have taken some major artistic license in anthropomorphizing the characters, how does the major premise stack up to biological reality? Do fish remember?
The short answer is yes. Fish can learn behavior and recall that behavior at a later date. Research studies on Goldfish (Carassius auratus) confirm what many home aquarists have long known – fish can learn and remember – especially with food as a reward. For example, Fernando Rodriguez and colleagues (1994) used mazes to test if Goldfish could be trained to find food using spatial orientation. They found overwhelming evidence that they could. Even when they were placed in an unfamiliar starting point in the maze, the Goldfish were able to reach their goal (food) based on visual cues.
More than just solving a maze, there’s a definite evolutionary advantage to being able to learn and remember, especially when food is involved. If a fish can navigate to food more quickly, it uses less energy to get there and will likely be able to eat more food than a fish that is randomly foraging and happens upon it. In the wild, there’s evidence that natural selection has led to sophisticated spatial memory skills. Bajer and colleagues (2010), for instance, tracked wild Common Carp (Cyprinus carpio) to show that they could quickly learn and remember the location of a food reward, even without visual cues, so that they could revisit the food source time and again.
Now, can fish learn to read, chart an escape plan, or feel human emotions? Well, as far as science can detect, no. But, those features sure do make for an entertaining story and I do think it’s safe to say that Dory’s famous words hold true as a mantra that many fish (and people!) live by: if you’re ever down, remember to “just keep swimming!”