Bycatch Reduction & Exclusion Strategies

Why do we need strategies to reduce bycatch?

Bycatch is the capture of non-targeted marine species accidentally caught in many fisheries with the commercially valuable targeted seafood species. These unwanted species, including cetaceans, sharks, sea turtles and seabirds are discarded and thrown back into the ocean, either dead, dying or injured, wasting valuable ocean resources and dishonouring sentient marine life (see Bycatch & Incidental Capture of Cetaceans under Impacts).

Bycatch contributes to increased incidental mortality rates in cetaceans, from large baleen whales to small dolphins and porpoises. The Yangtze River Dolphin or Baiji (Lipotes vexillifer) is declared functionally extinct. The ‘critically endangered’ Eubalaena glacialis (North Atlantic Right Whale) (see Entanglements & North Atlantic Right Whales under Impacts), Cephalorhynchus hectori māui (Māui Dolphin) and Phocoena sinus (Vaquita) are on the brink of extinction (see Gillnet Fishing & Vaquita Porpoises under Impacts).

Bycatch reduction strategies and recommendations

Many scientists, government agencies and the commercial fishing industry believe bycatch to be an acceptable and unavoidable consequence of providing seafood for human consumption, and invest in research, development and technological innovation to reduce unintentional capture of non-targeted species by fisheries and its associated environmental impact.

Bycatch research seeks to determine if incidental capture harms species and populations but results usually only require an official response if a particular species or population is negatively impacted by incidental capture (see Gillnet Fishing & Vaquita Porpoises and Entanglements & North Atlantic Right Whales under Impacts).

The United Nations Food and Agriculture Organization’s Code of Conduct for Responsible Fisheries (FAO 1995) advises how to report and reduce incidence of bycatch. Article 8.4.5 of Fisheries Operations and Article 12.4 of Fisheries Research specifically address bycatch.

UN FAO encourage the development and implementation of technologies and methods to reduce bycatch, discourage fishing gear and practices that produce bycatch (including fish aggregation devices or FADs with high rates of bycatch) and promote fishing gear and practices that increase survival rates of non-targeted species.

Reliable and accurate bycatch data must be collected to aid in fisheries assessments, “including data on bycatch, discards and waste”, and provided to relevant countries and fisheries organisations.

Bycatch Reduction Devices (BRDs)

Bycatch reduction devices or BRDs are specific modifications to a trawl specifically designed to reduce bycatch. Bycatch reduction strategies involve modification of existing fishing gear, to allow the captured non-target species to escape without sustaining injury or being killed.

Bycatch reduction devices (BRDs) is also used as the collective name for tools or specially designed equipment (and their associated strategies) that aim to minimize the incidence of bycatch in a fishery and reduce the number of non-targeted species caught unintentionally.

Many devices and strategies are being utilised in fisheries around the world, including TEDs, BEDs, ‘on-demand’ ropeless fishing gear and tracking and removal of ghost nets.

Turtle Excluder Devices (TEDs)

Turtle Excluder Devices or TEDs are designed to assist sea turtles to escape ‘active’ fishing nets if they are unintentionally caught (see Bycatch & Incidental Capture of Cetaceans under Impacts). TEDs consist of an angled grid of metal bars and mesh that sits inside the neck of a trawl net and acts as a barrier, allowing the target species to pass between the bars for collection at the back of the net, while guiding sea turtles and larger animals (sharks and rays), towards a flap in the mesh above or below the grid, where they can escape.

TEDs are mandatory in the Australian Commonwealth’s Northern and Torres Strait Prawn trawl fisheries. A study evaluated commercial use and impact of TEDs and BRDs on tropical marine environments in Australia’s northern prawn trawl fishery and found that nets using a TED only reduced sea turtle bycatch by 99%, while nets using a combination of a TED + BRD reduced sea turtle bycatch by 100% (Brewer et al. 2006).

Bird Exclusion Devices (BEDs)

Strategies to reduce seabird bycatch in longline fisheries (see Longline Fishing & Pelagic Seabirds under Impacts) include setting of lines after dark (night setting), use of heavily weighted hooks that sink quickly (line weighting) and streamers (bird-scaring lines).

Night setting – setting of longlines after dark is advised as most seabirds are active and feed during the day, although some species forage and hunt at night

Line weighting in pelagic and demersal longline fisheries – weighted lines deliver hooks to the required depth in the water column or on the seabed needed to capture the target species

Bird-scaring lines – a tori or streamer with a buoy attached is towed behind a vessel to create a visual and physical barrier that deters seabirds from entering the line setting zone

‘On-demand’ (ropeless) fishing gear

The Ropeless Consortium project by Woods Hole Oceanic Institution claims that this new technology eliminates the vertical fishing lines and buoys used in fishing methods where a trap, pot, barrel or net settles on the ocean floor and is used to capture lobsters and crabs, but commonly traps other marine species, including baleen whales and sea turtles.

Instead of fishing apparatus being attached to a line or rope suspended in the water column, it settles on the seafloor ‘ropeless’, and is either accompanied by a buoy or inflatable lift bag containing lines that return to the surface when ‘called’ by a sound signal sent from the boat to the fishing apparatus via acoustic release technology.

The technology is being hailed as beneficial for the survival of the ‘critically endangered’ Eubalaena glacialis (North Atlantic Right Whale), a baleen whale species currently being driven further north due to warming waters in traditional feeding grounds, right into the path of the lobster fishing grounds with its millions of fishing lines (see Entanglements & North Atlantic Right Whales under Impacts).

Ghost net retrieval and recycling

Many organisations are finding new and innovative ways to retrieve and recycle abandoned fishing nets (and plastic bottles), including re-purposing nylon into sustainable and ethical fashion items, including swimwear. Australia’s Ocean Zen led the way in the recycling of ghost nets into swimwear. Econyl use regenerated nylon from ghost nets and other waste to create a range of recycled products.

Ocean Voyages Institute in the USA has committed to removing 1,000,000 pounds (500 tons) of ghost nets and plastic debris from the Great Pacific Garbage Patch. Their 2020 haul retrieved 340,000 pounds (170 tons) of ghost nets and plastic waste from the ocean.

Ghost Nets Australia works with Australian Indigenous communities to remove ghost nets from the ocean and rescue entangled marine organisms, including sea turtles, uses satellite technology to track the journey of ghost nets around the world and has created a repository of information that catalogues data on ghost nets, including mesh size.

© 2016 – 2021 Seafood Free September


BirdLife International (2012) Simple changes to fishing methods can get seabirds off the hook. Downloaded from on 09/08/2021

Bycatch Management Information System (BMIS),

David Brewer, Don Heales, David Milton, Quinton Dell, Gary Fry, Bill Venables, Peter Jones, The impact of turtle excluder devices and bycatch reduction devices on diverse tropical marine communities in Australia’s northern prawn trawl fishery, Fisheries Research, Volume 81, Issues 2–3, 2006, Pages 176-188, ISSN 0165-7836,


FAO. Code of Conduct for Responsible Fisheries Rome, FAO. 1995. 41 p.

Ghost Nets Australia,

Ocean Voyages Institute,

Ocean Zen,

Ropeless Consortium – Towards whales without rope entanglements (Woods Hole Oceanographic Consortium),