IF YOU want to know a salmon鈥檚 social status just gaze into the whites of its
eyes.
Hayley Suter and her colleagues from the University of Glasgow鈥檚 fish biology
unit studied the sclera, or 鈥渨hites鈥�, of Atlantic salmon鈥檚 eyes, and found that
the colour was linked to the social status, belligerence and hunger of each
fish. Dominant fish had light, cream-coloured sclera that only darkened if they
fell ill. Low-status fish had dark sclera that lightened only after they ate a
meal or won a battle.
Just a tiny amount of food made a noticeable change, says Suter, who reports
her results this week in Glasgow at the annual meeting of the Association for
the Study of Animal Behaviour. 鈥淚t鈥檚 amazing what difference a couple of worms
can make,鈥� she says.
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