Fixed-location riverine hydroacoustics as a method of enumerating migrating adult Pacific salmon: comparison of split-beam acoustics vs. visual countingHermann J. Enzenhofer, Norm Olsen and Timothy J. MulliganAquat. Living Resour., 11 2 (1998) 61-74DOI: https://doi.org/10.1016/S0990-7440(98)80062-4