Bigeye tuna

1. What is it?

Bigeye tuna (Thunnus obesus) are predatory, migratory, schooling fish found in the tropical and subtropical waters of the Pacific, Atlantic and Indian Oceans. Juveniles and sub-adults can be found near the surface whilst adults tend to stay in deeper waters of around 300 m to 500 m. The species is listed as Vulnerable on IUCN’s list for threatened species. Bigeye tuna in the Atlantic Ocean is considered to be overfished with fishing pressure above sustainable levels. Bigeye tuna in the Indian Ocean is considered to be fully fished with fishing pressure at sustainable levels.

2. How was it caught or farmed?

Bigeye tuna are caught using pelagic longline fishery gear. Pelagic longlines consists of a double-line system suspended at different depths covered in baited hooks and which are several kilometers long. Bycatch of seabirds, fish, sharks and turtles are a major challenge within the fishery as many of these species are considered to be endangered, threatened or protected (ETP) species. Catches of sharks by the fishery in recent years have increased substantially, with sharks making up more than 60% of the catch in 2016.

3. Where is it from?

Atlantic Ocean

Bigeye tuna are harvested by South Africa in the Atlantic Ocean. Due to its migratory nature and global demand, bigeye tuna are managed by Regional Fisheries Management Organizations (RFMOs). The Atlantic Ocean component is managed by the International Commission for the Conservation of Atlantic Tunas (ICCAT). Member countries or co-operating non-member countries are then responsible for ensuring the implementation and adaptation of the recommended quotas and regulations. Effectiveness of the management of the Atlantic Ocean component is considered to be ineffective as scientific recommendations have not been followed. Management in South Africa is considered as largely effective; however there are concerns surrounding the management of bycatch species.

Indian Ocean

Bigeye tuna is harvested by South Africa in the Atlantic Ocean. Due to its migratory nature and global demand, bigeye tuna are managed by Regional Fisheries Management Organizations (RFMOs). The Indian Ocean component is managed by the Indian Ocean Tuna Commission (IOTC). Member countries or co-operating non-member countries are then responsible for ensuring the implementation and adaptation of the recommended quotas and regulations. Effectiveness of the management of the Indian Ocean component is considered largely ineffective as scientific recommendations have not been implemented effectively. Management in South Africa is considered as largely effective, however there are concerns surrounding the management of bycatch species.

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