Spawning behavior and spatial distribution of Atlantic herring on Georges Bank revealed by ocean acoustics waveguide remote sensing

An ocean acoustics waveguide remote sensing (OAWRS) system was deployed in the Gulf of Maine, near Georges Bank to image Atlantic herring and other fish population from September–October 2006. OAWRS provides spatially unaliased imaging of herring over wide areas, spannning over 100 km diam. Migration and spawning behavior of Atlantic herring were observed using OAWRS over several diurnal periods, including massive movements on and off the bank to spawn. Measurements made simultaneously with a conventional fish‐finding echosounder (CFFS) and a multibeam sonar provide the depth distribution and local 3‐D morphology, respectively, of the herring schools in the water column. Concurrent trawl surveys provide identification of the fish species. Measurements made by OAWRS and CFFS systems are highly correlated. Examples will be provided of the co‐registration between the two systems over a one‐week period. Calibration of the OAWRS system using CFFS estimates of fish population densities, along with a full‐field scattering model that takes into account both coherent and incoherent scattering from a fish group, is discussed. Resonance scattering behavior of herring is observed in the OAWRS system with significant changes in scattering amplitude over the 300 Hz to 1.5 kHz frequency range of the OAWRS system.