Small fish with strong personalities win food fights...

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When food is short, having a strong personality can be more useful than size, if you're a fish.

New research suggests that when it comes to predicting the outcome of a fight, the big guy doesn’t always win.

Scientists at the University of Exeter and Texas A and M University found that when fish fight over food, personality traits such as aggression could be more important than strength when it comes to survival.

The study, published in the journal Behavioral Ecology and Sociobiology, found that regardless of their initial size, it was the fish that tended to have consistently aggressive behaviour — or personalities — that repeatedly won food and as a result put on weight.

Dr Alastair Wilson from Biosciences at the University of Exeter said: "We wondered if we were witnessing a form of Napoleon, or small man, syndrome. Certainly our study indicates that small fish with an aggressive personality are capable of defeating their larger, more passive, counterparts when it comes to fights over food. The research suggests that personality can have far reaching implications for life and survival."

Sheepshead swordtails (Xiphophorus birchmanni) were placed in pairs in an aquarium, food was added and their behaviour captured on film. The feeding contest trials were carried out with both male and female fish. The researchers found that while males regularly attacked their opponent to win the food, females were much less aggressive and rarely attacked.

No fish were distressed or received physical injury during these experiments.

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