Hydroacoustics is used broadly to assess fish populations in marine and freshwater systems. Large-scale surveys often employ multiple vessels to complete a survey. Vessels can be a source of variation in multi-vessel surveys, and accounting for this variation is critical to precise and accurate assessments, whether as indices or measures of absolute abundance. We examined areal and volumetric density estimates, area backscattering coefficient (ABC), and mean target strength (TS) produced by three vessels in Lake Erie along three cross-lake transects in July 2014. Our study showed positive correlation in areal ABC, mean TS, and density among vessels; however, there was an almost 30 % higher density obtained with the largest vessel, on average. As a result, vessel choice could contribute to variation and/or bias in forage fish surveys deploying multi-vessels conducted on Lake Erie. Additionally, in some situations, differential depth patterns of fish contributed to vessel related differences in survey results suggesting a difference in vessel avoidance behaviors among targeted forage species, primarily emerald shiner Notropis atherinoides and rainbow smelt Osmerus mordax. This work demonstrates the potential magnitude of differences among vessels and highlights the need to identify and account for or otherwise control for these effects when monitoring or managing fisheries through standardized hydroacoustic assessments surveys.
|Title||Hydroacoustic survey standardization: Inter-vessel differences in fish densities and potential effects of vessel avoidance|
|Authors||Mark D. DuFour, Patrick Kočovský, J Deller, Paul W. Simonin, Lars G. Rudstam|
|Publication Subtype||Journal Article|
|Series Title||Fisheries Research|
|Record Source||USGS Publications Warehouse|
|USGS Organization||Great Lakes Science Center|