Acoustic sampling of various fish stocks and the acoustic characteristics of fish targets are being investigated as part of the Marine Acoustics Program at the University of Washington. An important outgrowth of this research is the development of a free‐floating acoustic system which is being used to help index the North Pacific salmon population. This is an uplooking system which operates at 250 kHz. Average target size of the migrating salmon is about − 30 dB within the aspect angles encountered in the sample volume. Acoustic source level and TVG receiver sensitivity were adjusted for that average size, but a fairly wide range of target‐size fluctuation can be accommodated (±10–15 dB). Studies of relative abundance indicate that the population density in particular areas is related to the spawning migration to Bristol Bay, Alaska, the following year thus providing an index of population abundance [D. E. Rogers, Fish Rec. Inst. Circ. ♯70‐7 (1970)]. A second acoustic system is now being developed for use in Bristol Bay to generate population data upon which to base the day to day management of the fishery so that catch and escapement are optimized.