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, juvenile bigeye and yellowfin tuna, and some smaller species of tuna, none of which are desired in the catch, also end up as bycatch.
Bycatch may be fish or other animals. They may be commercially valuable, or have no or little commercial value.
Bycatch is one of the biggest threats to marine biodiversity
Incidental bycatch is 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.
FADs to be constructed to prevent animals becoming entangled from 2020
In December 2018, the WCPFC introduced a new rule to minimise the harm caused by fish-aggregating devices (FADs), while allowing commercial fishing to continue to be profitable.
From 1 January 2020, 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.
But 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.
Bycatch also results in economic losses
Bycatch results in economic losses in damaged fishing gear, lower catches of targeted species, and fishing restrictions being imposed. There is a growing body of research into avoiding bycatch:
- Overview of fishing methods, Pacific Community (SPC), 2010
- Purse seine bycatch mitigation techniques, WCPFC, 2010
- Bycatch in longline fisheries for tuna and tuna-like species: A global review of status and mitigation measures, WCPFC, 2014
- At-sea experiment to evaluate the effectiveness of multiple mitigation measures on pelagic longline operations in western North Pacific, WCPFC, 2013
- Mitigating seabird bycatch during hauling by pelagic longline vessels, WCPFC, 2014
- At-sea experiment to develop the mitigation measures of seabirds for small longline vessels in the western North Pacific, WCPFC, 2015
Sharks and turtles
- A review of shark bycatch mitigation in tuna longline fisheries, WCPFC, 2014
- Analysis of sea turtle mitigation measure effectiveness in tuna longline fisheries, WCPFC, 2015
Best practice on board vessels
International Seafood Sustainability Foundation (ISSF) has a range of online tools, including videos and guidebooks to support the uptake of best practice onboard vessels:
- ISSF bycatch-handling videos for sharks, seabirds and turtles
- ISSF guidebooks for skippers describe the suggested best practices related to bycatch mitigation and handling, and include for purse seine and longline fishing.