Towards a standard operating procedure for fishery acoustic surveys in the Laurentian Great Lakes, North America

Abstract Rudstam, L. G., Parker-Stetter, S. L., Sullivan, P. J., and Warner, D. M. 2009. Towards a standard operating procedure for fishery acoustic surveys in the Laurentian Great Lakes, North America. – ICES Journal of Marine Science, 66: 1391–1397. Acoustic surveys are conducted annually in all five of the Laurentian Great Lakes and Lake Champlain to assess forage-fish abundance. The main target species are rainbow smelt (Osmerus mordax), alewife (Alosa pseudoharengus), and several coregonine species (Coregonus spp.). The Great Lakes Fishery Commission sponsored an Acoustic Study Group from 2002 to 2006 to discuss common problems and suggest standardized methods across these lakes. The study group produced a set of recommendations, available as a Great Lakes Fishery Commission Special Publication and on the web, that use in situ target strength (TS) to scale volume backscattering. Here, we review these recommendations with special attention to four often-overlooked topics of interest to all acoustic users, namely issues associated with first, the choice of thresholds for both TS and volume-backscattering strength, second, different settings for single-echo detection algorithms for measures of in situ TS, third, those taking account of measuring in situ TS in dense fish concentrations, and finally, detection limits.