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 A large illegal drift net caught on some obstruction on the sea floor. © Jane Dermer

A large illegal drift net caught on some obstruction on the sea floor. © Jane Dermer

Bycatch

Kilometres and kilometres of nets trawling our oceans are deadly. Not only do they entrap intended fish species; they also capture other marine animals that unwittingly stray into their path. This grisly incidental catch, known as bycatch, sees scores of marine turtles, dolphins, dugongs, sharks and seabirds hauled up onto the decks of fishing vessels and then tossed overboard dead or dying.

Globally, bycatch is thought to be the leading cause of death for cetaceans (whales and dolphins). Some populations are even likely to become extinct because of their repeated encounters with fishing gear. But many of these deaths and injuries can be avoided.

Good fisheries management takes an ecosystem-based approach. It acknowledges that fishing impacts on non-target species and manages those effects in a responsible manner. Good fisheries management is also based on sound science, which is playing a growing role in addressing the bycatch problem. Such measures couldn't come sooner for many protected species.

Impacted species

 

 

 

Impacts

 

Dugongs and inshore dolphins die from entanglement in the gill nets used to catch tropical species like barramundi, threadfin salmon or sharks. This occurs particularly on the Great Barrier Reef and Kimberley Coast.

Sharks and rays are targeted by various net fisheries but are also taken as bycatch in line and trawl fisheries, where post-capture mortalities are not well understood. This also occurs predominantly in the Great Barrier Reef and Kimberley regions.

Marine turtles are captured by net and trawl fishing activities. Trawl interactions have reduced significantly with the introduction of mandatory turtle excluder devices and other bycatch reduction devices used by the Queensland and Northern Prawn fisheries.

 

What we're doing

WWF-Australia is tackling bycatch on a number of fronts. We're actively developing and implementing safer fishing gear, pushing for stronger bycatch legislation and educating consumers about the issue.

 

Causes

 

Fishing cannot occur without some unintended bycatch. It's unavoidable. However, many fisheries continue to permit unselective fishing gear, with disastrous consequences.

Particularly high relative levels of bycatch are associated with bottom trawling, which has the potential to physically damage benthic sponge, coral and seagrass communities on the sea floor. Longlines and gill nets also commonly cause the drowning deaths of marine mammals and turtles. Nets lost at sea are rarely recovered, posing an ongoing risk for years to come.

Where Illegal, Unreported and Unregulated (IUU) fishing occurs, pirate fishers completely ignore regulations on net mesh sizes, quotas, permitted fishing areas and measures to mitigate bycatch. We will never know how many marine species they leave in their wake.

However, improvements in spatial management, vessel electronics (to allow skippers to steer clear of sensitive habitats) and gear modifications (including turtle excluder devices) are available and have helped trawl industries to significantly reduce bycatch levels. Strong leadership within sections of the Australian trawl fisheries have identified a range of solutions in the Northern Prawn Fishery and the South East Trawl Fishery.

The vaquita population has been declining steadily due to accidental bycatch in gillnets. © Chris Johnson

© Chris Johnson 

 
 

 

How you can help 

• Purchase MSC-certified seafood products. If unavailable, request them as a means of rewarding those fisheries that have taken the appropriate steps to certify their fishery. 

 

• Support campaigns promoting better fishing practices.

 

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Pole and line tuna and baitfish fishery project, Indonesia. Bitung, Sulawesi, Indonesia. May 2016 © Paul Hilton / IPNLF / WWF-Aus

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