We have recently started a series of studies to test the effects of high intensity LFA sonar on fishes. These studies, which tested the effects of an actual LFA sonar element, examined the changes in hearing capabilities, structure of the ear, and the effects on many other organ systems including the swim bladder and brain.

The first results of the study have now been published.

• Popper, A. N., Halvorsen, M. B., Kane, E., Miller, D. D., Smith, M. E., Stein, P., and Wysocki, L. E. (2007). The effects of high-intensity, low-frequency active sonar on rainbow trout. J. Acoust. Soc. Am., 122:623-635.

Additional data on several other species are now being prepared for publication.  These results show that while there is some loss of hearing in channel catfish, it is not permanent. There is also no effect on hearing in several additional species including a sunfish, perch, and bass.

In no case have we found any affect on auditory tissues of the inner ear or on non-auditory tissues when we did histopathology. There was no effect on other organ systems -- for example, the swim bladder in fish exposed to the sonar signal was completely intact. Moreover, all animals survived the experiments and none died, even several days after exposure.

The sound levels used in these experiments approached those that fish would encounter close to an active LFA source. However, the exposure during experiments were far more substantial than any a fish would encounter in that we exposed fish to multiple replicates of very intense sounds, whereas any fishes in the wild would encounter sounds from a moving source, and successive emissions from the source would decrease intensity as the ship moved away from exposed fish.