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 acoustic s is the deficiencies of the same alternate techniques that must be used to collect ground truth data. However, such data are often required for biolo gical information such as species composition, body size and spawning condi tion. In addition, since acoustic techniques are not universally accepted, ground truth information was sometimes needed to establish confidence in th e results. Many different approaches are used to obtain ground truth data. Examination of these results provides some interesting insights into the ch aracteristics of both the acoustic and the ground truth techniques and sugg ests some principles fur ground truth efforts used in conjunction with acou stics surveys. The appropriate role of ground truth efforts is not only ver ification, 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 l ikely to be inadequate. We recommend multiple methods for ground truth, so that inadequacy of individual techniques is to some extent compensated by s upplementary methods. This requires a reorientation of planning for most fi sheries acoustic surveys. (C) 2000 Elsevier Science B.V. All rights reserve d.