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 betw een a few genus of dolphin (Stenella and Delphinus) and yellowfin tuna (Thu nnus albacares) to locate and capture the tuna. Identification of a mechani sm which facilitates the tuna/dolphin bond may provide a means of exploitin g the bond and capturing tuna without catching dolphin. To investigate if t una may be attracted to low-frequency sounds produced by dolphins, source l evels of bottlenose dolphin (Tursiops truncatus) jaw pops, breaches, and ta il slaps were experimentally measured and used to estimate the maximum rang e at which yellowfin could detect similar sounds produced by pelagic specie s. The effective acoustic stimulus to the tuna was defined as the maximum o ne-third-octave level between 200 and 800 Hz, the frequency range where T. albacares is most sensitive. Spherical spreading was assumed to predict tra nsmission 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) d B re. 1 mu Pa-m, respectively, which resulted in estimated detection ranges of 340-840 and 660-1040 m, respectively. Tail slaps had lower source level s [max. 141 (+/-3) dB re: 1 mu Pa-m] and a maximum detection range of appro ximately 90-180 m. [S0001-4966(00)03001-0].