Abstract

We analyzed acoustic data collected with 120kHz along 7 cross-lake transect in July 2005. Acoustics signals from fish were removed from the mysid acoustics using a filter that removes pixels larger than a minimum back scattering value. Shipboard light strongly affects acoustic returns and only data collected with no light could be used for mysids. The distributions of mysids were patchy with few animals nearshore, and a concentration of animals around the 100 m depth contour. This occurred along most transects. Mysids abundance obtained with acoustics were comparable to those obtained with nets. The large-scale spatial distribution was also compared with large-scale distribution of mysids obtained with net samples in November of 2005 by DFO. By using our approach of filtering acoustics data, it is possible to obtain whole lake abundance estimates of this important component of the Ontario food web at the same time as the annual fish survey conducted by OMNR and NYSDEC. We recommend that this analysis be incorporated into the standard analysis applied to the acoustics data.