Investigations on the D. S. L. in oceanic waters have been considered in the light of recently acquired data on the structure of the air bladder in bathypelagic fishes. From this it has been suggested that much of the reverberation of supersonic pulses used in echo-sounding may come from layers of these oceanic fishes, particularly from those possessing an air bladder....
Marshall, Norman B.. 1951. "Bathypelagic fishes as sound scatterers in the ocean." Journal of Marine Research 10, (1). https://elischolar.library.yale.edu/journal_of_marine_research/733