Propagation of damselfish (Pomacentridae) courtship sounds

Many damselfishes perform a courtship behavior known as the signal jump, in which they rise in the water column and then rapidly swim downward while producing a pulsed sound. Pulsed sounds produced during the signal jump of the damselfish Dascyllus albisella were analyzed to determine whether they were correlated with the signal jump distance or speed, and how they changed with propagation. No statistical relationship was found between signal jump speed or distance with the number of pulses, pulse period, or change in the peak frequency of pulses in a call. If echoes were present in the sound, the change in echo delay would likely have been too small for damselfish to detect. Sounds attenuated with distance such that the signal-to-noise ratio decreased from 17-25 dB at 1 to 2 m to 5-10 dB at 11 to 12 m. It is unlikely that D. albisella can detect sounds at or beyond 11-12 m from the sound source, based on noise masking data from other fishes. Pulse period is least affected by propagation when compared to peak frequency, pulse duration, interpulse interval, and coefficient of variation of pulse amplitudes within a call. These results suggest that the sound produced during the signal jump functions over short distances and that the pulse period provides the most reliable basis for signal identification. (C) 1997 Acoustical Society of America.