SHOALING fish don’t like being in a minority but are tolerant of those that
are.
Nina Peuhkuri of Helsinki University found that three-spined sticklebacks
prefer to join shoals with fish the same size as them. A fish that stands out in
a shoal is at greater risk of being singled out by predators and may also
endanger other fish. Yet when Peuhkuri gave sticklebacks the choice of joining a
shoal of uniform fish or a shoal containing a few odd fish, they showed no
preference (Behavioral Ecology and Sociobiology, vol 46, p 307).
