401
tones, white noise, band-passed noise. Air guns and pile driving pulses can produce
rapid increases and decreases in pressure in a very short period of time and are usually characterized by peak pressure (Parkes and Hatton 1986 ; Popper and Hastings
2009 ). Sonars are transient signals (because they are from a moving ship) with frequency sweeps over time (Popper et al. 2007 ). Because of the different properties of
these sound sources, measures other than the root-mean-square (RMS) of the SPL
may be required to accurately predict hearing loss in fi shes. Two potential alternative measures are cumulative sound energy or the sound exposure level (SEL) (see
Hastings and Popper 2005 for a discussion of this topic).
4.2 Effects of Anthropogenic Sound Sources
Relatively few studies have examined the effect of anthropogenic sound sources on
fi sh hearing. McCauley et al. ( 2003 ) were the fi rst to show that anthropogenic sound
can cause sensory hair cell damage in fi sh ears. They exposed caged pink snapper
( Pagrus auratus ) to signals from a towed airgun (simulating a passing seismic vessel). Their ears exhibited considerable hair cell loss at both 18 h and 58 days after
exposure, but no hearing tests were performed to quantify hearing loss. Popper et al.
( 2005 ) reported hearing loss in fi shes following exposure to a seismic airgun array,
with threshold shifts varying between species. The fi shes were exposed to a mean
received SPL of 205–209 dB re 1 μPa (peak) and a mean SEL of 176–180 dB re 1
μPa
2 s per airgun shot. Lake chub ( Couesius plumbeus ) exhibited the greatest threshold shifts, while adult northern pike ( Esox lucius ) were intermediate, and broad
whitefi sh ( Coregonus nasus ) showed no hearing loss. This pattern was related to
baseline hearing thresholds, with the most sensitive species ( C. plumbeus ) exhibiting the greatest shift (Fig. 5 ). Hearing loss increased with the number of seismic
blasts that the fi sh were exposed to, but in all cases hearing thresholds returned to
normal within 24 h. These same fi sh were examined for sensory hair cell damage
and none was detected (Song et al. 2008 ). This suggests that any damage in the
fi shes may have occurred at an individual hair cell level as in mammals where seismic blasts can cause broken tip links between the hair cell stereocilia which disrupts
mechanotransduction and leads to hearing defi cits (Indzhykulian et al. 2013 ). Such
subtle damage is not easily detectable and can only be visualized by high power
scanning electron microscopy.
Popper et al. ( 2005 ) examined the effects of high intensity sonar on rainbow trout
( Oncorhynchus mykiss ). Fish were exposed to a U.S. Navy Surveillance Towed
Array Sensor System (SURTASS) Low Frequency Active (LFA) sonar with a maximum received RMS SPL of 193 dB re 1 μPa
2 s for 324 or 648 s. The trout exhibited
a 20 dB threshold shift at 400 Hz, but, similar to Song et al. ( 2008 ), no obvious
damage to the inner ear sensory epithelia or other non-auditory tissues was found.
This work was extended by adding data for three additional species, largemouth
bass ( Micropterus salmoides ), yellow perch ( Perca fl avescens ), and channel catfi sh
( Ictalurus punctatus ) (Halvorsen et al. 2013 ). Threshold shifts were evident for the
Causes and Consequences of Sensory Hair Cell Damage and Recovery in Fishes
tones, white noise, band-passed noise. Air guns and pile driving pulses can produce
rapid increases and decreases in pressure in a very short period of time and are usually characterized by peak pressure (Parkes and Hatton 1986 ; Popper and Hastings
2009 ). Sonars are transient signals (because they are from a moving ship) with frequency sweeps over time (Popper et al. 2007 ). Because of the different properties of
these sound sources, measures other than the root-mean-square (RMS) of the SPL
may be required to accurately predict hearing loss in fi shes. Two potential alternative measures are cumulative sound energy or the sound exposure level (SEL) (see
Hastings and Popper 2005 for a discussion of this topic).
4.2 Effects of Anthropogenic Sound Sources
Relatively few studies have examined the effect of anthropogenic sound sources on
fi sh hearing. McCauley et al. ( 2003 ) were the fi rst to show that anthropogenic sound
can cause sensory hair cell damage in fi sh ears. They exposed caged pink snapper
( Pagrus auratus ) to signals from a towed airgun (simulating a passing seismic vessel). Their ears exhibited considerable hair cell loss at both 18 h and 58 days after
exposure, but no hearing tests were performed to quantify hearing loss. Popper et al.
( 2005 ) reported hearing loss in fi shes following exposure to a seismic airgun array,
with threshold shifts varying between species. The fi shes were exposed to a mean
received SPL of 205–209 dB re 1 μPa (peak) and a mean SEL of 176–180 dB re 1
μPa
2 s per airgun shot. Lake chub ( Couesius plumbeus ) exhibited the greatest threshold shifts, while adult northern pike ( Esox lucius ) were intermediate, and broad
whitefi sh ( Coregonus nasus ) showed no hearing loss. This pattern was related to
baseline hearing thresholds, with the most sensitive species ( C. plumbeus ) exhibiting the greatest shift (Fig. 5 ). Hearing loss increased with the number of seismic
blasts that the fi sh were exposed to, but in all cases hearing thresholds returned to
normal within 24 h. These same fi sh were examined for sensory hair cell damage
and none was detected (Song et al. 2008 ). This suggests that any damage in the
fi shes may have occurred at an individual hair cell level as in mammals where seismic blasts can cause broken tip links between the hair cell stereocilia which disrupts
mechanotransduction and leads to hearing defi cits (Indzhykulian et al. 2013 ). Such
subtle damage is not easily detectable and can only be visualized by high power
scanning electron microscopy.
Popper et al. ( 2005 ) examined the effects of high intensity sonar on rainbow trout
( Oncorhynchus mykiss ). Fish were exposed to a U.S. Navy Surveillance Towed
Array Sensor System (SURTASS) Low Frequency Active (LFA) sonar with a maximum received RMS SPL of 193 dB re 1 μPa
2 s for 324 or 648 s. The trout exhibited
a 20 dB threshold shift at 400 Hz, but, similar to Song et al. ( 2008 ), no obvious
damage to the inner ear sensory epithelia or other non-auditory tissues was found.
This work was extended by adding data for three additional species, largemouth
bass ( Micropterus salmoides ), yellow perch ( Perca fl avescens ), and channel catfi sh
( Ictalurus punctatus ) (Halvorsen et al. 2013 ). Threshold shifts were evident for the
Causes and Consequences of Sensory Hair Cell Damage and Recovery in Fishes