The Airborne Streak Tube Imaging LIDAR (ASTIL) was evaluated for use in detecting schools of tuna in Eastern Tropical Pacific (ETP) waters in order to aid in reducing bycatch of dolphin associated with yellowfin tuna.  Three airborne experiments were conducted, and data were collected for southern bluefin tuna, yellowfin tuna, akule (trachiurops crumenophthalmus), giant bluefin tuna (GBFT), and dolphin.  (Two of the airborne experiments were funded directly by this research.  One southern bluefin tuna experiment was only provided with data analysis supported by this research.)  The LIDAR signature of tuna was studied and extended to an evaluation of fish and fish school detection of GBFT using STIL experimental data.  The utility of fish school detection was confirmed for GBFT in terms of detection statistics for binary hypothesis testing and also by direct implementation of a three-dimensional matched-filter algorithm.  Based on the GBFT observations, modeled performance estimates were made for yellowfin in the ETP for an upgraded ASTIL system.