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Product Awareness fishing - NT Fisheries: Reef Fish Research

Recent scientific data from the recreational, charter and commercial sectors, combined with anecdotal evidence from Territory anglers, has shown that the sustainability of many popular reef fish species is under threat, particularly in heavily fished areas.

Rapid advances in technology, such as improvements in GPS, side and down imaging, longrange weather forecasts as well as a high rate of information sharing among anglers, mean that fish stocks can be targeted and fished more efficiently. Many reef fish species possess biological traits that make them vulnerable to over fishing: schooling behaviour, slow growth rates and a susceptibility to being caught and harvested before becoming sexually mature.

One of the potential main contributors to fish stock declines is from recreational fishers replicating the conservation process that has worked so well for barramundi – catch and release. However, catch and release does not work for many of our vulnerable reef fish species, which suffer the lethal effects of barotrauma when caught from deep water.

NT Fisheries say deep-water anglers should catch and keep what they need for a feed, and then target other species.

The catch and release ethic has long been embraced by Territory anglers with recent survey data indicating that a staggering 70 per cent of all barramundi caught, many of them under the legal minimum size limit, are released back into the waterway. It is an unwritten law that metre-long barra are released, in the knowledge that only sexually mature females grow to that length.

This admirable catch and release ethos has unfortunately flowed over into our reef fishing practices where fishers think they’re doing the right thing by releasing small or excess reef fish. Data from the 2010 NT Recreational Fishing Survey showed anglers release about 60 per cent of all reef fish however, current research clearly shows that many of these fish are unlikely to survive when caught in water depths greater than 10 metres due to barotrauma.

Barotrauma is a condition not unlike a scuba diver rising to the surface with the bends. Gases in the fish’s body expand as it is brought up, inflating the swim bladder, which then pushes the internal organs out the fish’s orifices. Outwardly, the fish can display bloating in the abdomen or bulging eyes. The most common symptom is the stomach protruding from the fish’s mouth. Even fish not showing signs of barotrauma may have suffered fatal internal injuries.

I’m sure if we were honest with ourselves, anyone who has reef fished at some stage or another has witnessed the sight of a released fish floundering around on the surface at the back of the boat, unable to swim back to the bottom. While we would all like to think that once the fish sinks or floats out of view it will miraculously receive a new lease on life and return to business as usual, this is generally not the case. Results from recent golden snapper research using underwater cameras help confirm this.

Researchers used holding cages at a range of depths from eight metres to 25 metres. The fish were caught using standard recreational gear, lowered back down to the bottom, and observed for half an hour to assess their recovery.

The ensuing footage showed that fish caught from depths down to 10 metres quickly recovered and resumed swimming and functioning immediately, whereas once depths of over 10 metres were trialled, significant signs of barotrauma were observed in the fish behaviours. The footage reaffirmed what autopsies and reflex tests had previously indicated with the most common injury, a ruptured swim bladder, severely inhibiting the fish’s ability to regulate buoyancy and swim upright. Not surprisingly, underwater footage also revealed how vulnerable reef fish are to predation once released, with sharks and large cod frequently making an appearance around the cages.

With the results of this research in mind, anglers need to adopt the same level of responsibility and protective stewardship they have demonstrated for barramundi, albeit by not practicing catch and release when targeting our vulnerable reef fish stocks. Catch only what you need for a feed, and then move on and target other species. If we do this we will go a long way to protecting Northern Territory reef fish stocks and maintain exceptional fishing opportunities for many years to come.

For more information on barotrauma research and to view the underwater footage visit the website


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