An airborne lidar using commercial, off-the-shelf components was developed by the National Oceanic and Atmospheric Administration for fisheries’ surveys. We make several test flights of the system and develop several signal processing techniques to discriminate between the returns from fish and from small particles in the water. We use these techniques to produce several products of use to fisheries’ biologists. Examples are presented of gray-scale images similar to those produced by acoustic echo sounders, of maps of spatial distributions of fish, and of vertical profiles of fish biomass. © 2001 Society of Photo-Optical Instrumentation Engineers.