The goldfish syndrome may also partly explain problems associated with fish stocking. Salmon cultivated in fish farms are usually unable to adapt to original river habitats. "The fry most likely to survive in fish farms are those who are the first to rush to the feed dispensers. In a natural environment, such foolhardy risk-takers are usually caught by predators in no time," says Jussi Koskinen, a doctoral student from the University of Helsinki Department of Biosciences.

A cultured fish can also be discerned from a natural fish on the basis of their brains. According to Koskinen, the size of the brain in relation to body size grows faster in fry born out of natural fish than in cultured fries. In addition, the cerebellum, which plays an important role in motor control, is larger in fry originating from wild parents and those reared in an enriched environment. Group-living improves vision