A clupeid fish can detect ultrasound

Abstract

It has been suggested that most teleost fishes cannot detect sounds higher than 2 or 3 kHz (ref. 1). However, we report here that at least one species of clupeid fish (herrings and shads), the American shad (Alosa sapidissima), can detect sounds up to 180 kHz. We speculate that clupeids are able to detect the ultrasonic clicks of one of their major predators, echolocating cetaceans2. Blueback herring swim away from echosounders, indicating that they may be able to detect ultrasound3, and ultrasound is used to keep several clupeids from entering water intakes of electric power-generating plants4. But it was not clear whether the fish were detecting the ultrasonic frequencies, or whether they were detecting lowerfrequency side-bands associated with the pulsed sounds. To test the range of frequencies detected, we measured auditory thresholds of shad ( Fig. 1) using a classical conditioning technique in which the fish learned to reduce their heart rate when they detected a sound (Fig. 2a)5. We trained five fish using tones from 0.2 to 180 kHz (Fig. 2b). Measurement of the frequency spectrum of the signal showed that the sound contained only pure tones.