179
adapted for adult fi sh and juveniles, allowing for the better understanding of how
auditory capabilities change during ontogeny. In addition, the PPI assay is also
potentially useful in comparative hearing studies that examine closely related species and species that possess hearing specializations. We suggest that future
researchers explore the use of psychoacoustic methods to assess fi sh hearing and
consider the following areas of research mentioned briefl y below.
1. In order to maximize the effi ciency and accuracy of fi sh psychoacoustic studies,
we suggest researchers should carefully consider the most appropriate associative (conditioning) method and stimulus presentation method available in order
to assess the hearing capability of a given fi sh species. We also highly recommend the use of adaptive stimulus presentation methods, such as the staircase
method, whenever possible to determine auditory threshold estimations, in order
to minimize the number of stimulus presentations and reduce habituation of the
measured behavioral response.
2. Future psychoacoustic fi sh studies should incorporate the latest automated methods to measure and analyze the movements/responses of animals. Video-based
automation and tracking have been utilized to measure long-term locomotor
behavior in rodents (Noldus et al. 2001 ), Drosophila (Branson et al. 2009 ), and
larval zebrafi sh (Fontaine et al. 2008 ). Application of these tracking methods and
their use with behavioral psychoacoustic paradigms to assess fi sh hearing can
provide rapid data collection, analysis, and allow for more dynamic behavioral
experiments that may provide a better understanding of auditory capabilities and
perception in fi shes.
3. Our psychoacoustic data from larval D. rerio and G. aculeatus suggest that auditory sensitivity is different across taxa, even before the development of accessory
auditory structures in species that are “hearing specialists.” The use of behavioral
methods, particularly PPI assays can be useful in understanding how development of the auditory system and perceptual ability differ within and across species. Many species of larval fi sh use sound as a settlement cue (Simpson et al.
2004 ), but the hearing ability of such species has not been well characterized; the
PPI assay could be a potential tool used to determine which pelagic larval fi sh
are capable of hearing abiotic and biotic sound cues and provide a way to characterize the auditory sensitivity of various pelagic larval fi shes.
4. Behavioral methods can inform us about auditory perception in fi sh species that
are too delicate to investigate by other methods such as electrophysiology. In
addition, psychoacoustic methods can be applied and used in longitudinal studies
to investigate the effects of seasonal differences in auditory perception, discrimination of relevant vs. non-relevant stimuli, and auditory stream segregation.
Longitudinal studies can also be used to assess auditory development and sensitivity within the same individuals using the same technique.
5. A prominent question in fi sh hearing is the effect of anthropogenic sound on
fi shes. Anthropogenic sounds can act as maskers, which may change the perceptual environment of fi shes, or can be loud enough to have profound short- and
long-term effects on the auditory systems such as causing short-term temporary
Revisiting Psychoacoustic Methods for the Assessment of Fish Hearing
adapted for adult fi sh and juveniles, allowing for the better understanding of how
auditory capabilities change during ontogeny. In addition, the PPI assay is also
potentially useful in comparative hearing studies that examine closely related species and species that possess hearing specializations. We suggest that future
researchers explore the use of psychoacoustic methods to assess fi sh hearing and
consider the following areas of research mentioned briefl y below.
1. In order to maximize the effi ciency and accuracy of fi sh psychoacoustic studies,
we suggest researchers should carefully consider the most appropriate associative (conditioning) method and stimulus presentation method available in order
to assess the hearing capability of a given fi sh species. We also highly recommend the use of adaptive stimulus presentation methods, such as the staircase
method, whenever possible to determine auditory threshold estimations, in order
to minimize the number of stimulus presentations and reduce habituation of the
measured behavioral response.
2. Future psychoacoustic fi sh studies should incorporate the latest automated methods to measure and analyze the movements/responses of animals. Video-based
automation and tracking have been utilized to measure long-term locomotor
behavior in rodents (Noldus et al. 2001 ), Drosophila (Branson et al. 2009 ), and
larval zebrafi sh (Fontaine et al. 2008 ). Application of these tracking methods and
their use with behavioral psychoacoustic paradigms to assess fi sh hearing can
provide rapid data collection, analysis, and allow for more dynamic behavioral
experiments that may provide a better understanding of auditory capabilities and
perception in fi shes.
3. Our psychoacoustic data from larval D. rerio and G. aculeatus suggest that auditory sensitivity is different across taxa, even before the development of accessory
auditory structures in species that are “hearing specialists.” The use of behavioral
methods, particularly PPI assays can be useful in understanding how development of the auditory system and perceptual ability differ within and across species. Many species of larval fi sh use sound as a settlement cue (Simpson et al.
2004 ), but the hearing ability of such species has not been well characterized; the
PPI assay could be a potential tool used to determine which pelagic larval fi sh
are capable of hearing abiotic and biotic sound cues and provide a way to characterize the auditory sensitivity of various pelagic larval fi shes.
4. Behavioral methods can inform us about auditory perception in fi sh species that
are too delicate to investigate by other methods such as electrophysiology. In
addition, psychoacoustic methods can be applied and used in longitudinal studies
to investigate the effects of seasonal differences in auditory perception, discrimination of relevant vs. non-relevant stimuli, and auditory stream segregation.
Longitudinal studies can also be used to assess auditory development and sensitivity within the same individuals using the same technique.
5. A prominent question in fi sh hearing is the effect of anthropogenic sound on
fi shes. Anthropogenic sounds can act as maskers, which may change the perceptual environment of fi shes, or can be loud enough to have profound short- and
long-term effects on the auditory systems such as causing short-term temporary
Revisiting Psychoacoustic Methods for the Assessment of Fish Hearing