Food for Thought Fish hearing and how it is best determined

Hearing, as defined by numerous investigators of vertebrate hearing, involves not only detection of a sound, but the ability to respond to the sound behaviourally. Thus, in order to understand what a fish (or any animal) hears, it is important to use behavioural methods that allow an animal to "tell the investigator" which sounds are detected and which are not. However, since the 1980's, most studies that suggest they are measuring fish hearing have used electrophysiological approaches to measure the response of the ear or lower levels of the central auditory system to sounds. In this paper, we argue that these electrophysiological measures do not represent hearing since they do not indicate what sounds a fish can potentially respond to behaviourally. Thus, while the electrophysiological measures provide some useful and interesting insights into fish sound detection mechanisms, the most valid measures of hearing sensitivity, and understanding which sounds (anthropogenic or otherwise) that fish are able to respond to, are obtained using behavioural studies. We also argue that these studies must be done in carefully designed acoustic setups so that the nature of the stimulus to which the fish responds is appropriate and well understood.