Publication Abstract

Acoustic tracking

G.P. Arnold

Acoustic tags are used to track marine fish because, unlike radio waves, sound propagates well in salt water. Simple ‘pingers’ transmit at regular pre-set intervals; transponders transmit on receipt of an external signal. Both types of tag can be used to telemeter physical or physiological data. The diameter of the tag and detection range both vary inversely with operating frequency, which ranges from 30 to 300 kHz. Tags can be attached externally, surgically inserted in the peritoneum, or ingested voluntarily. Fish tagged with acoustic tags can be tracked with a fixed hydrophone array or a series of moored buoys, from which data can be recovered by radio or satellite. High-resolution systems can be used to track the small scale of movements of fish in the vicinity of dams or barrages. Mobile tracking systems range from small boats fitted with rotatable, directional hydrophones to large research vessels towing a hydrophone array, or fitted with a sector scanning sonar. These tracking systems are labour intensive and development is increasingly towards automated listening stations, data storage tags, which record information at equivalent rates but avoid the need to follow the fish continuously for long periods, and remote data retrieval by satellite.

Reference:

G. P. Arnold (2000) Acoustic tracking. Proceedings Workshop on Fish Movement and Migration (Bendigo, Va, 28-29 September 1999)