Appetitive conditioning technique reveals behavioural limits to passage performance in fishes

Numerous environmental features have the potential to act as 'barriers' to fishes in the field. Passage of these 'barriers' depends on two main properties: willingness (behavioural) and physiological capacity. The physiological swimming capacity of fishes has been well studied. However, because most barrier research has focused on the population level effects of man-made barriers, little attention has been given to the behavioural aspects of fish passage. We used appetitive conditioning to create a simple laboratory based protocol to estimate behavioural limits to fish passage. We tested our protocol using barrier height (or passage space) as a model. Our protocol successfully identified behavioural limits in two species, juvenile rainbow trout, Oncorhynchus mykiss, and fathead minnows, Pimephales promelas. Our most interesting observation was that even a partial, submerged barrier had the potential to block fish movements. Our results suggest a potential use for conditioning techniques in assessing factors that constitute behaviour barriers to fishes. This information may help us to better predict fish movements in the field and may help us to design barriers that are more efficient at passing fishes.