Limited evidence of bias in acoustic surveys determined by surface vessel

Acoustic surveys are a critical tool for studying fish populations and can provide fisheries-independent data on spatially extensive fish populations. However, prior work has identified fish avoidance of survey ships, presumably in response to the noise radiated into the water column. Post-doc Thomas Evans, Lars Rudstam, Suresh Sethi, James Watkins, and collaborators recently published the largest test of bias in freshwater acoustic surveys, using saildrones deployed in Lakes Michigan and Huron. Saildrones are essentially silent vessels powered by wind and solar that were overtaken by traditional survey vessels. There was little evidence fish responded as powered ships approached the drone, and when transects were surveyed by drone or ship there were few systematic differences. This work suggests that the acoustic surveys in Lakes Michigan and Huron are not affected by fish avoidance. Fish avoidance of survey ships does not always occur and may be triggered by more than simply the noise the vessel radiates into the water column.

Evans, T.M., Rudstam, L.G., Sethi, S.A., Warner, D.M., Hanson, S.D., Turschak, B., Farha, S.A., Barnard, A.R., Yule, D.L., Dufour, M.R., O’Brien, T.P., McDonnell, K.N., Watkins, J.M., Koproski, S.R., Wells, S.E., Dieter, P.M., Kocher, E., Roberts, J.J., Senczyszyn, S.A., Esselman, P.C. 2023. Fish avoidance of ships during acoustic surveys tested with quiet uncrewed surface vessels in the Great Lakes. Fisheries Research. 267:106817.