Ground truth and target identification for fisheries acoustics

One of the most troublesome problems fur fisheries acoustic surveys is the acquisition of ground truth data. A major incentive fur the use of acoustics is the deficiencies of the same alternate techniques that must be used to collect ground truth data. However, such data are often required for biological information such as species composition, body size and spawning condition. In addition, since acoustic techniques are not universally accepted, ground truth information was sometimes needed to establish confidence in the results. Many different approaches are used to obtain ground truth data. Examination of these results provides some interesting insights into the characteristics of both the acoustic and the ground truth techniques and suggests some principles fur ground truth efforts used in conjunction with acoustics surveys. The appropriate role of ground truth efforts is not only verification, but also to aid interpretation of the acoustic data. We conclude that the use of a single method to obtain ground truth data is generally likely to be inadequate. We recommend multiple methods for ground truth, so that inadequacy of individual techniques is to some extent compensated by supplementary methods. This requires a reorientation of planning for most fisheries acoustic surveys. (C) 2000 Elsevier Science B.V. All rights reserved.