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High levels of
sound are known to have significant effects on the auditory
system and overall physiology of humans and other animals.
Although there has been recent concern about the effects of
anthropogenic sounds, such as those produced by Navy sonar
or seismic surveys, on marine mammals, little is known about
how such intense underwater sounds affect other marine life
such as fishes. My research focuses on how loud sounds damage
the ears and hearing capabilities of fishes (Please see "Effects
of Intense Sound on the Ear of Fishes"). I examine
damage to the sensory cells (hair cells) of fish ears using
scanning electron microscopy (SEM) and the effect on fish
hearing using electrophysiological methods (auditory brainstem
response).
I have examined
noise-induced auditory threshold shifts (TTS) in two species
of fishes that differ in hearing ability- tilapia (a poor
hearing generalist) and goldfish (a hearing specialist). My
results show that noise differentially affects species that
differ in hearing sensitivity and also confirms the hypothesis
that hearing specialists are more greatly affected by noise
exposure than are hearing generalists. The difference can
be explained by a linear relationship between TTS and sound
pressure level (SPL) above the fish’s baseline threshold.
The likely reason that tilapia did not exhibit threshold shifts
in response to 170 db re: 1µPa white noise and goldfish
did, is that TTS (and perhaps hearing damage) only occurs
when noise is a certain SPL above the fish’s baseline.
Because baseline thresholds for tilapia are 20-50 dB higher
than those of goldfish, one might expect 20-50 dB greater
SPLs (190-220 dB re: 1µPa) would be required to produce
the same threshold shifts as found in goldfish exposed to
170 db re: 1µPa. This linear threshold shift (LINTS)
hypothesis needs to be tested with more teleost species and
a broader range of noise SPLs, but may become a useful tool
for researchers examining how anthropogenic sounds might affect
fishes. Such a linear relationship for teleosts is consistent
with results for birds and mammals, but greater underwater
SPLs are required to induce a comparable TTS as found in birds
and mammals in air.
I am currently involved in multiple
projects examining the effects of anthropogenic sound on
fishes. Such projects include studying the effects of
Low-Frequency Active (LFA) sonar and seismic air-guns on
various fish species. Additionally, we are studying the
effects of aquaculture noise on the health and hearing of
rainbow trout at an intensive aquaculture facility at the
Freshwater Institute in West Virginia.
I am also interested
in using zebrafish (Danio rerio) as a model for hearing
loss in humans. Zebrafish has become an important vertebrate
model for examining inner ear defects since many mutations
affecting the development of the inner ear have already been
identified. Most of these defects occur early in development,
but many inner ear deficits in humans occur late in life.
We hope to find late-onset hearing deficit phenotypes in zebrafish.
In particular, I am examining the interaction between aging
and noise-induced hearing loss in zebrafish. Such background
data on wild type strains are needed if zebrafish are to be
a good genetic model of hearing loss in humans.
Goldfish (Carassius
auratus) is another model species that I am using to
understand the process of hair cell regeneration following
noise-induced trauma. Hair cells, the sensory cells of
the inner ear that transduce acoustic signals to neural
signals, can regenerate in fishes and birds, but not in
mammals. I am attempting to understand the relationship
between hearing loss and recovery, and hair cell loss and
regeneration in goldfish as a first step to understand how
hair cell regeneration occurs in fishes.
Note- starting
August 15, 2005, my new address will be:
Department of
Biology
Western Kentucky
University
Bowling Green, KY
42101
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Smith, M.E., Kane, A.S., and Popper,
A.N. 2004. Acoustical stress and hearing sensitivity in
fishes: does the linear threshold shift hypothesis hold water?
Journal of Experimental Biology 207:3591-3602.
Smith, M.E., Kane, A.S., and Popper,
A.N. 2004. Noise-induced stress response and hearing loss in
goldfish (Carassius auratus). Journal of Experimental
Biology 207(3):427-435.
Popper, A. N., Fewtrell, J., Smith, M. E.
and McCauley, R. D. 2004. Anthropogenic sound: effects on the
behavior and physiology of fishes. Marine Technology Society
Journal 37:33-38.
Popper, A.N., M.E. Smith, P. Cott, B.
Hanna, A. MacGillivray, M. Austin, D. Mann. In press. Effects
of exposure to seismic air-guns on fish hearing. Journal of
the Acoustical Society of America.
Smith, M.E. and L.A. Fuiman. 2004.
Behavioral performance of wild-caught and laboratory-reared red
drum Sciaenops ocellatus (Linnaeus) larvae. Journal
of Experimental Marine Biology and Ecology 302(1):17-33.
Fuiman, L.A., Cowan, J.H. Jr., Smith, M.E.,
and O’Neal, J.P. In press. Behavior and recruitment success in
fish larvae: variation with growth rate and the batch effect.
Canadian Journal of Fisheries and Aquatic Sciences.
Belk, M.C., Johnson, J.B., Wilson, K.W.,
Smith, M.E., and Houston, D. In press. Variation in
intrinsic individual growth rate among populations of
leatherside chub (Snyderichthyes copei): adaptation to
temperature or length of growing season? Journal of
Freshwater Ecology.
Smith, M.E. and L.A. Fuiman. 2003.
Causes of growth depensation in red drum, Sciaenops ocellatus,
larvae. Environmental Biology of Fishes 66:49-60.
Smith, M.E. and M.C. Belk. 2001.
Risk-assessment in western mosquitofish (Gambusia affinis):
do multiple cues have additive effects? Behavioral Ecology
and Sociobiology 51 (1):101-107.
Smith, M.E. 2000. The alarm response
of Arius felis to chemical stimuli from injured
conspecifics. The Journal of Chemical Ecology 26
(7):1635-1647.
*Fuiman, L.A., M.E. Smith, and V.
Malley. 1999. Ontogeny of routine swimming speed and startle
responses in red drum, with a comparison of responses to
acoustic and visual stimuli. Journal of Fish Biology 55
(supplement A):215-226.
Smith, M.E. and M.C. Belk. 1996.
Sorex monticolus. Mammalian Species 528:1-5. |
