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Acoustic Doppler current profilers (ADCPs) use the signal scattered back from small suspended drifting particles, such as suspended sediments and planktonic species, to measure water current velocity. Additionally, ADCPs detect signals scattered from fish and other pelagic organisms, but these signals are generally treated as noise and rejected during data processing. However, these rejected signals can contain information on fish movement, which presents an opportunity to extend the application of ADCP technology as a tool for monitoring fish activity. We compare discrete target counts made using an ADCP with those of a split‐beam echosounder in a region of high tidal currents in the Bay of Fundy. The comparison was achieved using a self‐contained bottom‐mounted frame equipped with both a 600‐kHz Teledyne RD Instruments Workhorse ADCP and a 120‐kHz BioSonics DTX Submersible split‐beam echosounder system. The discrete targets were identified using a combination of signal correlation and volume backscatter (SV) thresholds in the ADCP data and using a fish tracking algorithm in the split‐beam echosounder data. The resulting ADCP discrete target counts agreed with fish tracking counts made from the co‐located split‐beam echosounder. Notably, discrete targets recorded by the ADCP could be differentiated from entrained air using a high signal correlation threshold. This method can expand the application of ADCP data for biophysical assessments for fisheries management and could be of particular use in rivers and tidal channels. [ABSTRACT FROM AUTHOR]

Prior studies demonstrate that bottom velocity measurements from Doppler sonar systems are proportional to bedload transport rates. These observations suggest that acoustically based systems offer a capability for rapid sampling of bedload transport processes. Before these measurements can be fully utilized, validation and understanding of the sampling mechanism are essential. We explore the measurement mechanism through a series of laboratory trials with a field instrument, the multi‐frequency coherent Doppler profiler (MFDop). The MFDop system is a multi‐frequency (1.2–2.2 MHz), bistatic Doppler sonar that provides three‐component ensemble‐averaged velocity profiles over a ∼30 cm depth interval with up to 1 mm resolution at a rate of 50 profiles/sec. Tests of the MFDop system were carried out in the main flume in field‐scale conditions at the St. Anthony Falls Laboratory (SAFL) using 1 ms−1 mean flows over a mobile bed of sand with median grain size d50 = 0.4 mm. We find agreement between MFDop transport measurements and measurements based on bedform migration rates, and sediment traps built into the SAFL flume. Predictions using the Meyer‐Peter and Müller (1948) empirical equation closely match our observations while in contrast, predictions using the Nielsen (1992) equation are a factor of two higher. Key Points: Field‐scale laboratory trials demonstrate that bedload transport can be measured by bistatic coherent Doppler sonarAcoustic, bedform migration, sediment trap, and Meyer‐Peter & Muller estimates of bedload all agree [ABSTRACT FROM AUTHOR]