The Promise and Perils of Airborne Lidar

Airborne lidar uses short pulses of laser light to measure profiles of optical backscattering in the upper ocean.  It holds a promise of large-area surveys of epipelagic fishes that are faster and cheaper than those using surface vessels.  These surveys are better in that they are not affected by fish movements or vessel avoidance.  The main perils in the use of this technology are misidentification of lidar targets and errors in converting lidar signal level to biomass that could lead to large errors in survey results.  The smarter approach is an adaptive-survey design that combines the strengths of airborne lidar with those of acoustics and direct sampling from a surface vessel.  This survey design can use airborne results to more effective use costly ship days at sea.  I will present our experiences with airborne lidar detection of capelin, flying fish, jellyfish, mackerel, menhaden, sardines, and mixed schools.  One common feature of these investigations is that the distribution of epipelagic fish is highly variable in both time and space.  The speed of an aircraft can help resolve temporal and spatial scales of this variability, while slower surface surveys can interpret temporal variability as spatial.