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1 Introduction
The ability to detect underwater sounds is of vital importance for fi shes that use
their auditory and mechanosensory lateral line systems to mediate behaviors such as
prey detection, predator avoidance, and social communication, which are crucial for
survival and species perseverance. How do fi sh hear? How well do fi sh hear, and
how do we measure their hearing capabilities? These seemingly simple questions
have spawned decades-worth of research on the mechanisms, morphologies, and
behavioral functions of fi sh auditory systems, which have uncovered remarkable
diversity in structure and function even though only a limited number of the >30,000
species of fi shes have been examined thus far.
The methodologies researchers utilize to measure both spectral hearing range
and auditory thresholds in fi shes have undergone a historical progression from
behavioral techniques, which are laborious and slow to generate entire audiograms,
towards quicker electrophysiological techniques that allow audiograms to be completed within a few hours. How well do these different electrophysiological methods refl ect the true auditory capabilities of a particular species? What pertinent
information can we obtain from each method? Is one method better than another
and are the various methods comparable? These questions are diffi cult to answer
without substantial recording examples of different types performed under similar
experimental paradigms in diverse representative species. Towards this goal, we
present here a comparison of multiple electrophysiological recording methods in a
single damselfi sh species and use it as a framework for discussing the relative utility
of different physiological techniques for determining auditory capabilities in fi shes.
1.1 Methodologies Used to Measure Auditory Capabilities
in Fishes
Techniques used to determine various aspects of fi sh auditory abilities can be
separated broadly into two main categories, behavioral and electrophysiological.
Behavioral and psychophysical methods include assays such as avoidance (Tavolga
and Wodinsky 1963 ), operant (Yan and Popper 1991 ) and classical (Fay and
MacKinnon 1969 ) conditioning, startle response (Bang et al. 2000 ), and prepulse
inhibition (Bhandiwad et al. 2013 ). These behavioral techniques are advantageous
because they measure evoked responses resulting from the integration and perception of the entire auditory scene that is relayed to neural output circuits causing
whole animal behaviors. Some disadvantages of these behavioral methods, however, include long training periods and testing trials, unknown relative contributions of lateral line and inner ear components to the response, and the fact that not
all behavioral methods work for a particular fi sh species. In the early days, these
behavioral techniques dominated the world of fi sh bioacoustic research and were
perceived as the best way to measure hearing in all animals (Fay 1988 ).
Electrophysiological methods, on the other hand, include both minimally invasive
K.P. Maruska and J.A. Sisneros
1 Introduction
The ability to detect underwater sounds is of vital importance for fi shes that use
their auditory and mechanosensory lateral line systems to mediate behaviors such as
prey detection, predator avoidance, and social communication, which are crucial for
survival and species perseverance. How do fi sh hear? How well do fi sh hear, and
how do we measure their hearing capabilities? These seemingly simple questions
have spawned decades-worth of research on the mechanisms, morphologies, and
behavioral functions of fi sh auditory systems, which have uncovered remarkable
diversity in structure and function even though only a limited number of the >30,000
species of fi shes have been examined thus far.
The methodologies researchers utilize to measure both spectral hearing range
and auditory thresholds in fi shes have undergone a historical progression from
behavioral techniques, which are laborious and slow to generate entire audiograms,
towards quicker electrophysiological techniques that allow audiograms to be completed within a few hours. How well do these different electrophysiological methods refl ect the true auditory capabilities of a particular species? What pertinent
information can we obtain from each method? Is one method better than another
and are the various methods comparable? These questions are diffi cult to answer
without substantial recording examples of different types performed under similar
experimental paradigms in diverse representative species. Towards this goal, we
present here a comparison of multiple electrophysiological recording methods in a
single damselfi sh species and use it as a framework for discussing the relative utility
of different physiological techniques for determining auditory capabilities in fi shes.
1.1 Methodologies Used to Measure Auditory Capabilities
in Fishes
Techniques used to determine various aspects of fi sh auditory abilities can be
separated broadly into two main categories, behavioral and electrophysiological.
Behavioral and psychophysical methods include assays such as avoidance (Tavolga
and Wodinsky 1963 ), operant (Yan and Popper 1991 ) and classical (Fay and
MacKinnon 1969 ) conditioning, startle response (Bang et al. 2000 ), and prepulse
inhibition (Bhandiwad et al. 2013 ). These behavioral techniques are advantageous
because they measure evoked responses resulting from the integration and perception of the entire auditory scene that is relayed to neural output circuits causing
whole animal behaviors. Some disadvantages of these behavioral methods, however, include long training periods and testing trials, unknown relative contributions of lateral line and inner ear components to the response, and the fact that not
all behavioral methods work for a particular fi sh species. In the early days, these
behavioral techniques dominated the world of fi sh bioacoustic research and were
perceived as the best way to measure hearing in all animals (Fay 1988 ).
Electrophysiological methods, on the other hand, include both minimally invasive
K.P. Maruska and J.A. Sisneros