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 can be fish or other animals. Bycatch includes animals or fish that are commercially valuable, or not.

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 (See Turtles). 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 from becoming entangled in fishing gear (WWF); by another estimate, every year worldwide, about 7.3 million tonnes of marine life is captured as bycatch (from all fishing).

It also results in economic losses

Bycatch causes economic losses in damaged fishing gear, lower catches of targeted species, and fishing restrictions being imposed (Consortium for Wildlife Bycatch Reduction).


Sharks and turtles

Sharks in bycatch is a major problem in tuna fishing. Photo credit: Francisco Blaha

Best practice onboard 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: