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6 Acoustic Attraction
Long range (farfi eld) orientation studies began in the 1960s with Nelson and
Myrberg’s pioneering work on sharks, investigating the frequencies which attracted
distant sharks the best. Nelson and Gruber ( 1963 ) found that different species of
Carcharhinidae and Sphyrnidae were mostly attracted to low frequency (20–60 Hz)
pulsed sounds compared to higher frequency (400–600 Hz) pulsed sounds or low
frequency continuous sounds. Myrberg et al. ( 1969 , 1972 ) took this work a step
further and observed that sharks showed sensitivity to low amplitude irregular
pulsed sounds up to a frequency of 1000 Hz. The sharks also exhibited directional
responses beyond the visual range of the camera (>25 m), which highlights that they
were orienting to the sound stimulus well into what is typically thought of as the
farfi eld (Myrberg et al. 1969 ). The actual nature of the attraction remains to be
determined however, as sharks likely have little to no pressure sensitivity because
they lack any pressure sensitive ancillary hearing structures, such as a swim bladder.
Therefore, the particle motion component could be stimulating both the ear and
external mechanoreceptors.
More recently, ambient underwater sound has been shown to play a major role in
a key life history stage of many reef fi sh species—the transition from the larval
pelagic stage to the benthic juvenile/adult stage (see Montgomery et al. 2001, 2006
for review). The fi rst studies (Tolimieri et al. 2000 ; Simpson et al. 2004 ) employed
the use of light traps and showed that traps with a sound source (recordings of ambient reef noise collected at night when most larvae settle) consistently caught more
fi sh than silent traps. In free-swimming pelagic larvae followed by divers, it was
also demonstrated that pre-settlement larvae will orient to a reef at night and that
broadcast sounds can change their orientation behaviour, indicating that they can
use sound to orient to reef habitats up to 1000 m from the reef source (Leis et al.
2002 ; Leis and Carson-Ewart 2003 ). The next step was using binary choice experiments which showed that all reef fi sh tested could directionally orient themselves to
the sound source (Tolimieri et al. 2002 , 2004 ; Leis and Lockett 2005 ). This was
followed by patch reef experiments where reef fi sh settled onto the patch reefs associated with a sound source in greater numbers than silent patch reefs (Simpson et al.
2005 ). Not only do reef fi sh show a behavioural response towards sound, they also
have the hearing capability to be able to detect these sounds (Wright et al. 2005 ,
2008 , 2011 ). Combining the different hearing thresholds determined by Wright
et al. ( 2011 ) with the reef sound propagation model developed by Radford et al.
( 2011 ), larval reef fi sh have the capability to detect a reef from between 8–15 km
offshore. All these experiments highlight that sound plays a critical role as a long
distance orientation and settlement cue for reef fi sh and at these distances it is likely
that responses to sound are indeed likely dominated by true hearing responses
because of the steep attenuation of particle motion sources likely to stimulate the
lateral line at these distances (Figs. 1 and 3 ).
D.M. Higgs and C.A. Radford
6 Acoustic Attraction
Long range (farfi eld) orientation studies began in the 1960s with Nelson and
Myrberg’s pioneering work on sharks, investigating the frequencies which attracted
distant sharks the best. Nelson and Gruber ( 1963 ) found that different species of
Carcharhinidae and Sphyrnidae were mostly attracted to low frequency (20–60 Hz)
pulsed sounds compared to higher frequency (400–600 Hz) pulsed sounds or low
frequency continuous sounds. Myrberg et al. ( 1969 , 1972 ) took this work a step
further and observed that sharks showed sensitivity to low amplitude irregular
pulsed sounds up to a frequency of 1000 Hz. The sharks also exhibited directional
responses beyond the visual range of the camera (>25 m), which highlights that they
were orienting to the sound stimulus well into what is typically thought of as the
farfi eld (Myrberg et al. 1969 ). The actual nature of the attraction remains to be
determined however, as sharks likely have little to no pressure sensitivity because
they lack any pressure sensitive ancillary hearing structures, such as a swim bladder.
Therefore, the particle motion component could be stimulating both the ear and
external mechanoreceptors.
More recently, ambient underwater sound has been shown to play a major role in
a key life history stage of many reef fi sh species—the transition from the larval
pelagic stage to the benthic juvenile/adult stage (see Montgomery et al. 2001, 2006
for review). The fi rst studies (Tolimieri et al. 2000 ; Simpson et al. 2004 ) employed
the use of light traps and showed that traps with a sound source (recordings of ambient reef noise collected at night when most larvae settle) consistently caught more
fi sh than silent traps. In free-swimming pelagic larvae followed by divers, it was
also demonstrated that pre-settlement larvae will orient to a reef at night and that
broadcast sounds can change their orientation behaviour, indicating that they can
use sound to orient to reef habitats up to 1000 m from the reef source (Leis et al.
2002 ; Leis and Carson-Ewart 2003 ). The next step was using binary choice experiments which showed that all reef fi sh tested could directionally orient themselves to
the sound source (Tolimieri et al. 2002 , 2004 ; Leis and Lockett 2005 ). This was
followed by patch reef experiments where reef fi sh settled onto the patch reefs associated with a sound source in greater numbers than silent patch reefs (Simpson et al.
2005 ). Not only do reef fi sh show a behavioural response towards sound, they also
have the hearing capability to be able to detect these sounds (Wright et al. 2005 ,
2008 , 2011 ). Combining the different hearing thresholds determined by Wright
et al. ( 2011 ) with the reef sound propagation model developed by Radford et al.
( 2011 ), larval reef fi sh have the capability to detect a reef from between 8–15 km
offshore. All these experiments highlight that sound plays a critical role as a long
distance orientation and settlement cue for reef fi sh and at these distances it is likely
that responses to sound are indeed likely dominated by true hearing responses
because of the steep attenuation of particle motion sources likely to stimulate the
lateral line at these distances (Figs. 1 and 3 ).
D.M. Higgs and C.A. Radford