Effects of LFA and Mid-Frequency Sonar on Fish

We have conducted studies to test the effects of high intensity naval sonars on fishes. These studies, which tested the effects of an actual LFA Mid-Frequency sonar elements, 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 results of the study have now been published in three papers.

  • 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.

  • Kane, A. S., Song., J., Halvorsen, M. B., Miller, D. L., Salierno, J. D., Wysocki, L. E., Zeddies, D., Popper, A. N. (2010). Exposure of fish to high intensity sonar does not induce acute pathology. J. Fish Biol., 76:1825-1840.Link

  • Halvorsen, M. B., Zeddies, D. G., Ellison, W. T., Chicoine, D. R., and Popper, A. N. (2012). Effects of mid-frequency active sonar on fish hearing. J. Acoust. Soc. Am., 131:599-607. Link

In these studies we demonstrated that the high intensity sounds from both low frequency active sonar (around 300-500 Hz) and mid-frequency sonar (in our case 2,500 to about 4,000 Hz) did not result in mortality or damage to either the sensory cells of the ear or to non-auditory tissues (e.g., Kane et al., 2010).  Low frequency sonar resulted in some hearing loss by both channel catfish and rainbow trout, but less in several additional species (data being prepared for publication now). However, and most interestingly, not all rainbow trout showed a hearing loss. The results suggest strongly that some aspects of genetic background or development may have an impact on the susceptibility of fish to effects of high intensity sounds.  All catfish, and most rainbow trout, recovered from hearing loss.

The mid-frequency active sonar studies showed some temporary hearing loss in channel catfish at around 2,500 Hz, but not at other frequencies. There was no hearing loss in rainbow trout, which is not surprising considering that this species does not hear sounds above perhaps 1,000 Hz.

The sound levels used in these experiments approached those that fish would encounter close to an active LFA or MF 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.

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