Locating Fish within the Acoustic Beam Split beam transducers measure acoustic signals on four independent receivers that correspond to the quadrants of a circular transducer face. Differences in the time of arrival of an individual echo to each quadrant may be used to locate the off-axis angle of a fish target and its position within the acoustic beam. The air bladder is the primary sound-scattering component of fish. Changes in the shape and orientation of the air bladder strongly influence the target strengths of individual fish. Fish Acoustics Acoustic surveys of Great Lakes fishes are providing important information on prey fish abundance, biomass, and spatial distributions.
Horizontal axis is time.
Fish are highly aggregated at dusk but disperse in the water column at night. Similar data have been incorporated into salmonid growth models to determine how habitat quality in Lake Ontario changes over a variety of time scales. Fish Spatial Distributions Fish densities along a cross-lake transect section in Western Lake Ontario. Note the seasonal shifts in spatial distributions. Bay-wide Fish Abundance in Chesapeake Bay during April, July, and October 1996.