Trap versus net: Behavioural sampling bias caused by capture method in three-spined sticklebacks.

Abstract Wild-caught animals are often used in behavioural or other biological studies. However, different capture methods may target individuals that differ in behaviour, life history and morphology, thereby giving rise to sampling biases. Here, we investigated whether juvenile three-spined sticklebacks caught in a natural population by passive and active sampling methods using frequently used tools (i.e. trap and hand net) differ in behaviours related to cognition and personality. The fish caught by traps were more prone to take risks and shoal (i.e. bolder and more sociable), but smaller in size and mass than the fish caught by hand nets. Individual variation in boldness was greater in the fish caught by hand nets, suggesting that this active sampling method may capture more representative samples of the natural population. Our results show the importance of capture method to avoid sampling bias in behavioural studies using wild-caught animals.