Why and how do we track the movements of fish

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Exploring the secret lives of Victoria’s premier fisheries species

Why track fish?

Determining where, when and why fish move is critical in understanding the distribution and availability of fish for fishing, and forms a basis for the sustainable management of fisheries. Fish move for a variety of reasons, including spawning, feeding and to avoid unfavourable environmental conditions. Tracking the movements of fish enables scientists to identify valuable fish habitat and important spawning grounds, and also determine how fish are likely to respond to changes in the environment.

How do we track the movements of fish?

Until recently, the movements of fish have been investigated using conventional tags and catch/release fishing. Fish are tagged with an external tag that identifies the fish and provides a contact number for fishers lucky enough to (re)catch the fish. The results from conventional tagging can be used to estimate fish abundance and provide information on overall (net) movements of fish.

VicTag has been successfully tagging a wide variety of fish in Victorian waters since 1994. In some cases, fish have moved very large distances. For example, an Australian Salmon tagged at Portland on 7th of January 1995 was recaptured 1198 days later at Cheynes Beach, Albany in W.A. During this time, the fish had swum 2128 km to the west, grown around 200 mm, and weighed an estimated 2.5 kg.

To understand more about the fine-scale movements and habitat preferences of fish, a slightly different type of tag is needed. Acoustic telemetry is a relatively new and exciting alternative for tracking the movements of fish. Fish are implanted with an acoustic transmitter (pinger) that emits an ultrasonic signal (69kHz). Acoustic receivers (listening stations) listen for the ‘pinger’, and record and store the time, date and identity of fish as they swim past. The biggest advantage of acoustic tagging over traditional tagging methods is that fish do not have to be re-caught to provide information on their movements – fish only have to be ‘heard’ by a listing station. While acoustic tagging does not provide information on abundance or stock size (unless combined with traditional tagging methods), it does provide detailed, time and date integrated information on individual fish movements and habitat associations.

What to do if you catch a tagged fish?

All fish implanted with an acoustic transmitter have also been tagged with an external tag. These external tags are yellow in colour and inserted beside the dorsal fin. Printed on each yellow external tag is a unique code that identifies the fish, as well as a phone number (1800 652 598) to report the catch.

If a tagged fish is caught, we recommend that the fish be handled gently and released. If possible, fishers are encouraged to record the tag number, weight and length of the fish, as well as the time, date and place of capture – but only if this does not cause the fish too much stress.

If fishers are not able to release the fish alive, they are encouraged to store the frame (the fish carcass minus the fillets) by freezing and contact Dr Jeremy Hindell to arrange for the collection of fish for aging and chemical analysis.

Fishers who report a catch will receive a certificate which identifies the fish they have caught, and provides a summary of where and when the fish has moved.

Tagged fish

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