Source levels and estimated yellowfin tuna (Thunnus albacares) detection ranges for dolphin jaw pops, breaches, and tail slaps.
Tuna fishers in the eastern Pacific Ocean often exploit an association between a few genus of dolphin (Stenella and Delphinus) and yellowfin tuna (Thunnus albacares) to locate and capture the tuna. Identification of a mechanism which facilitates the tuna/dolphin bond may provide a means of exploiting the bond and capturing tuna without catching dolphin. To investigate if tuna may be attracted to low-frequency sounds produced by dolphins, source levels of bottlenose dolphin (Tursiops truncatus) jaw pops, breaches, and tail slaps were experimentally measured and used to estimate the maximum range at which yellowfin could detect similar sounds produced by pelagic species. The effective acoustic stimulus to the tuna was defined as the maximum one-third-octave level between 200 and 800 Hz, the frequency range where T. albacares is most sensitive. Spherical spreading was assumed to predict transmission loss with range. Breaches and jaw pops produced maximum one-third-octave source levels between 200 and 800 Hz of 153 (+/-4) and 163 (+/-2) dB re: 1 microPa-m, respectively, which resulted in estimated detection ranges of 340-840 and 660-1040 m, respectively. Tail slaps had lower source levels [max. 141 (+/-3) dB re: 1 microPa-m] and a maximum detection range of approximately 90-180 m.
Finneran
J J
JJ
Biosciences Division, Space and Naval Warfare Systems Center, San Diego, California 92152, USA.
Oliver
C W
CW
Schaefer
K M
KM
Ridgway
S H
SH
D000818:Animals; D004289:Dolphins / Q000502:physiology*; D004455:Echolocation / Q000502:physiology; D005399:Fishes; D007568:Jaw / Q000502:physiology*; D017603:Signal Detection, Psychological / Q000502:physiology*; D013016:Sound; D013623:Tail / Q000502:physiology*