Treacherous trail

GOLDFISH leave a tell-tale trail of eddies in their wake that could betray
them to predators. Horst Bleckmann of the University of Bonn and his colleagues
trained goldfish to swim across an aquarium. By adding glitter to the tank, the
researchers were able to watch the turbulence behind the fish. Some eddies
persisted for three minutes (The Journal of Experimental Biology, vol
203, p 1193). The researchers think that predators can read these trails.