Bycatch – Conserving marine diversity


Tuna fishing affects animals such as sharks, turtles, whales, dolphins, seabirds, and young tuna. The countries of the WCPO manage fishing practices to reduce how many of these animals are caught or injured.

Policy and Rules

Rules advise how to avoid bycatch, and how to release caught animals

The major rules for protecting marine animals while allowing for sustainable harvesting of tuna and other fish are decided by the Western and Central Pacific Fisheries Commission (WCPFC). It meets once a year to decide on rules and policies that support the management of the tuna fisheries of the Western and Central Pacific Ocean (WCPO). The rules are called conservation and management measures (CMMs). They are binding. The WCPFC also sets resolutions, which are recommended courses of action but are not binding.

The WCPFC is made up of three groups of countries: members, cooperating non-members, and participating territories. They are known collectively as CCMs. Among the members are the 14 small island developing states (SIDS) of the WCPO.

WCPFC maintains all CMMs and resolutions.

Some CMMs are directed at reducing harm to animals that are often caught during tuna fishing. These animals are known collectively as bycatch. The animals most likely to become bycatch are sharks, sea turtles, whales, dolphins, and seabirds. Many of these animals face extinction. Bycatch also includes juvenile tuna that are too young to harvest.


Seabird bycatch mitigation measures

Column A Column B
Side setting with a bird curtain and weighted branch lines Tori line
Night setting with minimum deck lighting Blue-dyed bait
Tori line Deep-setting line shooter
Weighted branch lines Management of offal discharge
Hook-shielding devices  


Extra rules for reducing bycatch cover fishing in PNA waters

Several agreements made by PNA members include provisions to protect species that are not targeted by vessels fishing for tuna or other sought-after fish. The species that are caught accidentally during fishing are known as bycatch.

The third arrangement for implementing the agreement states (in Article 1, paragraph 2) that no vessels are to deploy or service fish-aggregating devices (FADs) and associated equipment, or to fish by purse-seining vessels on floating objects between 0001 GMT on 1 July and 2359 GMT on 30 September each year. This rule is partly directed at reducing bycatch related to the use of FADs.

A 2011 amendment to this arrangement prohibits fishing, or any related activity, designed to catch tuna associated with whale sharks.


Managing fishing practices to reduce bycatch

The Pacific Islands Forum Fisheries Agency (FFA) facilitates regional cooperation for the sustainable use of tuna. It was established in 1979 to help countries to sustainability manage the fishery resources that fall within their 200-mile exclusive economic zones. FFA develops the capacity of members to monitor and take actions to reduce their bycatch.

Scanning for diving birds preventing birds from becoming caught is better than releasing them afterwards. Photo: Francisco Blaha.

The Western and Central Pacific Fisheries Commission (WCPFC) maintains the Bycatch Management Information System (BMIS), which focuses on lessening the numbers of animals caught as bycatch when fishing for tuna and billfish.

BMIS is useful for fishery managers, fishers, scientists, observers, and educators and anyone else who is interested in how fisheries are managed. The main focus is on highly migratory species that breed slowly: mostly seabirds, sharks and rays, sea turtles, and marine mammals.

BMIS is also a reference and educational tool, which can be used to support the adoption of science-based management measures so that bycatch is managed sustainably.

Management information in BMIS provides context and rationale for the development of bycatch conservation and management measures.

The Oceanic Fisheries Programme (OFP) of the Pacific Community assists the WCPFC and in the development of the BMIS. It also helps to manage the monitoring and reporting of bycatch.

PNA members apply sustainable free-school fishing

PNA promotes the practice of catching skipjack and yellowfin tuna in free-swimming schools, that is without using fish-aggregating devices (FADs). Free-school fishing is certified by the Marine Stewardship Council (MSC). It is said to be more sustainable than fishing around FADs, because it limits the amount of bycatch, which may include sharks, rays, turtles, and dolphins.

Best Practices

FADs must be constructed to prevent animals becoming entangled

Animals that are not targeted during tuna fishing but are inadvertently caught or entangled in fishing gear are known collectively as bycatch. The most commonly caught animals are juvenile bigeye and yellowfin tuna, some smaller species of tuna, seabirds, dolphins, whales, sharks, rays and turtles.

Tuna fishing affects marine animals such as sharks, turtles, whales, dolphins, and seabirds when they are inadvertently caught (as bycatch) during normal fishing operations. As well, some kinds of tuna that are not desired in the catch end up as bycatch. They include juvenile bigeye and yellowfin tuna, and some smaller species of tuna.

Bycatch may be commercially valuable, or have no or little commercial value. Either way, bycatch generally results in economic losses from damaged fishing gear, lower catches of targeted species, and fishing restrictions being imposed.

Bycatch is also one of the biggest threats to marine biodiversity, with as much as 40% of all animals caught being discarded. Some estimate that about 300,000 small whales, dolphins, and porpoises, and hundreds of thousands of turtles, more than 3 million sharks, and 160,000 seabirds die every year after becoming entangled in fishing gear. By another estimate, every year, about 7.3 million tonnes of marine life is captured as bycatch from all fishing worldwide.

In the WCPO, two of the best practices in minimising harm to species not targeted by tuna vessels are:

  • rules to enforce the use of non-entangling fish-aggregating devices (FADs)
  • PNA rules that prohibit the use of FADS for three months a year.

PNA countries prohibit the use of FADs for three months a year

The member countries of the Parties to the Nauru Agreement prohibit the use of fish-aggregating devices (FADs) in PNA watersfor three months each year, from 1 July to 30 September.

A more detailed prohibition has also been agreed for the WCPO by the Western and Central Pacific Fisheries Commission.

WCPFC rules for bycatch-friendly FADs

All existing and new FADs must be constructed so that animals such as sharks and turtles cannot become entangled in them. The WCPFC also encourages construction using only natural or biodegradable materials.

Avoid using mesh

Under the new rules, FAD makers should avoid using mesh.

However, if they do use it, they must ensure that the mesh, when stretched, is no larger than 7 cm. It must be secured snugly to the raft, so it does not hang loose.

If used in the ‘tail’ that hangs beneath the raft, mesh must be securely tied in a sausage shape so that animals cannot get caught in it. Tails should be weighted so they hang vertically or almost vertically in the water.

A rope or a sheet of canvas are considered better options than mesh.

Need to reduce plastic waste in oceans

The promotion of natural materials is aimed at reducing the amount of plastic waste drifting in the oceans, and washing up on reefs and coasts. FADs and other lost fishing gear contribute to this pollution.

FADs are important in purse-seine fishing for tuna

Fish-aggregating devices are one of the most important methods used to catch tropical tuna. They exploit the habit of many kinds of fish, including tuna, of clustering around floating objects, whether natural (e.g. driftwood, dead whales) or artificial. Tuna will congregate around a FAD in schools numbering thousands.

Large FADs are used extensively in commercial purse-seine fishing because they increase the likelihood of successful fishing operations. Thousands of drifting FADs are put into the Western and Central Pacific Ocean every year.

They also cause the catch of juvenile tuna and loss of endangered animals

The widespread use of FADs has resulted in many problems. As well as catching the desired tuna, fishing fleets often also unintentionally take too many small juvenile tuna, which are part of the school but are too young to breed. They also take other fish that have no commercial value, as well as sharks and turtles.

Turtles and sharks, many of which are endangered, sometimes become tangled in the mesh used in FADs and die.

New FADs designed to reduce bycatch and plastic pollution

The WCPFC commissioned research on the best designs and materials for FADs to reduce bycatch. More research is needed, and the WCPFC will amend the rules for fishing in the western and central Pacific Ocean as better designs come on line.

Best practice in the design of biodegradable, non-entangling FADs. Image credit: ISSF.


Three categories of FADs, from the best kind of non-entangling design to the worst. Image credit: ISSF.

Research and Training

Research and training on bycatch to protect marine life

The Oceanic Fisheries Programme of the Pacific Community (SPC) provides training programs for fisheries officers, observers and others in the small island developing states (SIDS). This assists them with monitoring, recording and reporting bycatch. It also conducts research on bycatch that helps the nations of the Western and Central Pacific Ocean effectively manage the protection of species not intended to be caught.

Baseline research on bycatch

Ecological risk assessments identify the animals that are most vulnerable to being inadvertently caught during fishing. The most vulnerable are animals that interact more with the tuna targeted in fishing or with fishing vessels, and that also reproduce slowly. The most common ones are sharks, turtles, marine mammals, and seabirds.

Bycatch numbers vary with fishing methods. It is hard to get sufficient data on bycatch for methods of fishing where there are fewer official observers, but baseline research summarises what is known. The Western and Central Pacific Fisheries Commission makes bycatch data for the WCPO publicly available.

In the purse-seine fishery, about 12% (by weight) of the total catch is bycatch. Bycatch from fishing of free-swimming tuna is lower on average (1.0%) than bycatch from fishing using fish-aggregating devices, or FADs (2.0%). Dolphins are rarely encircled by purse seines in the WCPO; the most significant bycatch species are sharks. In 2017, SPC produced a report on bycatch in purse-seine fisheries for the years 20032016. SPCs Neville Smith provides an overview of the report (2.09 mins).

Rates of bycatch in the longline fishery are considerably higher, at around 30% of the total catch. However, much of this is retained bycatch (called byproduct), which has some commercial value.

Most sharks are caught in the longline fishery, with the purse-seine fishery estimated to catch only 23% of the total. Most of the WCPFCs designated key shark species they include shortfin mako, silky, oceanic whitetip, thresher, porbeagle, hammerhead, and whale sharks must be conserved, and action is occurring to reduce bycatch of these species.

Billfish continue to form a significant proportion of the non-target catch, but are mostly retained due to their commercial value.Seabird deaths due to longlines are very low in the tropical WCPO compared with deaths in higher latitudes, where albatrosses and petrels, in particular, are prone to becoming caught. But low observer coverage on many longline fleets means that the number of interactions is largely unknown.

Other research projects

The sustainable tuna fisheries part of the Common Oceans ABNJ Program includes a significant component on sharks. It centres on the Pacific, and is led by the WCPFC Secretariat. It ran until 2019.

Image of a J hook and circle hook used for pelagic fishing to prevent turtles and other non-target species from being hooked.

Simple changes in hook shape can mean that non-target species don’t become bycatch (CC BY-SA 3.0).


Resources on bycatch and FADs

You can find news stories, popular articles, opinion pieces and blog posts on bycatch on the Bycatch news and views page.

Fact sheets

Technical papers


Sharks, rays, turtles and dolphins



Posters and videos

  • ISSF bycatch-handling videos for sharks, seabirds and turtles
  • The Pacific Community presents a documentary that explains a typical longline expedition to catch tuna in the Western and Central Pacific Ocean, from setting out to the processing of the catch back in port. It features interviews with fishers and observers, and explains the role of the observer (16.42 mins).