A bi-static sonar system design has been developed by Scientific Fisheries Systems, Inc. (SciFish) to detect schools of tuna at longer ranges and for a greater portion of the day than was previously attainable. This system included the ability to detect tuna schools not associated with other animals, such as dolphins or birds. The design incorporates current technology at both a low technical risk and low cost by using techniques developed for military use and Commercial-Off-the-Shelf(COTS) equipment. This system was developed with inputs from the tuna fishing fleet to maximize usefulness and minimize the added workload on personnel at sea.