Report of the Study Group on Fish Avoidance to Research Vessels (SGFARV)

In the early 1980s fisheries acoustics began to be one of the most used survey meth‐ods for evaluation of fish populations. It had many advantages, but a preliminary condition was required to allow considering the data collected as representative of the populations: that fish was not avoiding the vessel. Pioneer works from Olsen et al. (1983a, b) described clearly the problem. A series of measurement on fish avoidance were performed and gave very variable results, from no avoidance to huge avoid‐ance. The question was recognised as critical for the survival of the acoustic methods.