Feature story

Keeping seals out of fishing nets

To stop seals getting into trawl nets, fishing operators can put a gate in the throat of the net that stops the seals swimming in but still lets the fish get caught. This gate is known in fisheries terminology as a seal excluder device.

A trawl net is shaped like a cone or funnel with a wide opening to catch fish and a narrow closed end called a cod-end. If seals do manage to swim into the wide open end of the net as it is going down to fish they are stopped by the seal excluder device.

While seal excluder devices are very good at saving the seals’ lives, the fish can get out through the escape hatch too.

Since seals can only dive to 150 metres and fishing often takes place a lot deeper than that it makes sense to only use the seal excluder device when the net is hauled through the seal
swimming zone.

During the 2010-11 year AFMA has worked closely with industry to develop an innovative new seal excluder device. The device was designed by AFMA’s Michael Tudman (Manager of the Bycatch Program) and his team and was built by Petuna Sealord Deepwater Fishing, New Zealand, with extra funding provided by the Australian Government’s Caring for our Country program and CSIRO. This device is known as the “TuddySED”.

The wings of the TuddySED net are held closed as it descends through the seal dive zone using net binding. These bindings break away after the net is beyond seal swimming depth, allowing the net to spread open for the fishing operation. When the full fishing net is hauled back up towards the surface the boat’s electronic monitoring system detects when it is entering the seal zone. The boat’s skipper pushes a button to trigger an acoustic device that closes the net again.

The TuddySED was first tested at the Australian Maritime College flume tank. Since then the TuddySED has been trialled at sea and the preliminary results are extremely positive.

AFMA staff have worked in partnership with industry during 2010-11 to develop the “TuddySED”, an acoustically triggered seal excluder device.

AFMA staff have worked in partnership with industry during 2010-11 to develop the “TuddySED”, an acoustically triggered seal excluder device.