SHORT COMMUNICATION AN ACOUSTIC TELEMETRY SYSTEM FOR MONITORING THE HEART RATE OF PIKE, ESOX LUCIUS L., AND OTHER FISH IN THEIR NATURAL ENVIRONMENT

Heart rate can be telemetered from fish using FM radio transmitters (Nomura & Ibaraki, 1969), FM acoustic transmitters (Wardle & Kanwisher, 1974), acoustic pulsed transmitters (Priede & Young, 1977), electromagnetic transmitters (Priede et al. 1985) and acoustic transponders (Storeton-West et al. 1978). Most of these systems transmit only over short distances or cannot be used with the standard equipment used in animal-tracking studies. This paper describes an acoustic transmitter which emits a high-power pulse triggered by the R wave of the electrocardiogram (ECG) and is compatible with normal field equipment for tracking fish. The design is based on the concept of Priede & Young (1977) but has a 75 kHz output usable in fresh or salt water, modern integrated circuits with low power consumptions, and lithium batteries. The circuit (Fig. 1A) is made on a miniature printed circuit board using chip-type surface-mounting components. Power is provided by a two-cell lithium battery (Duracell PX28L) which is centre-tapped to provide a nominal ±3V supply. For safety reasons, care should be taken not t