His research focuses on the use of active acoustics to study the distribution and abundance of nekton and zooplankton in marine and freshwater systems, as well as the bottom-up and top-down processes that affect these distributions. In addition to field surveys, his research interests include: improving the accuracy of acoustic scattering models; use of passive acoustics to study fish, mammal, and invertebrate ecology; and predator-prey (fish/zooplankton and marine mammals/seabirds/pinniped) dynamics. He has conducted acoustic surveys for more than two decades from vessels ranging from rowboats to 300 ft ice-breakers and led research projects throughout the world from the lakes of the Sierra Nevada mountains to the coastal waters of New York City to the coral reefs of Jamaica to the Western Antarctic Peninsula.