This amazing fish is an apex predator that can reach up to 4.58 m in size, and has special warm-blooded physiology adaptations (regional endothermy) to allow it to hunt at high speeds in cold water.

In brief

• Rarely recorded around Northern Ireland, but some records from north coast.
• Previously listed as Endangered but after strict management and conservation measures, now Near Threatened within European context.
• Vulnerable to overfishing due to being a prized catch, so measures should ensure populations stay at least at current levels.

Species description: A very large fish, with a dark blue back and upper sides, and silvery white belly and lower sides. The second dorsal fin is red-brown in colour and is larger than the first, which is yellow to blue It has very short pectoral fins. It has a crescent-shaped tail.

Life cycle: Tuna are long-lived (up to around 40 years) and reach maturity at age 4-5. Adults make huge migration journeys and exhibit high site fidelity, returning to the same site each year to breed. Eastern Atlantic tuna breed in the Mediterranean Sea from June-August. They are batch spawners, with high mortality rates. Juveniles that do survive grow rapidly and move inshore, however growth slows down once fish is an adult taking over 10 years to reach two thirds of their maximum size.

Similar species: Unlikely to be confused with any other species found in this region.

How to see this species: This is a migratory species and can be seen off the west coast of Ireland and north coast of Northern Ireland.

Current status: Declining. It has been suggested recent sighting in NW and W of Northern Ireland might indicate an expansion of the range of this species, however this needs to be investigated.

Why is this species a priority in Northern Ireland?

• Criterion 1: Internationally listed species.
• Criterion 2: Decline based on available data and expert judgement.

Threats: At risk from overfishing without use of careful conservation measures and management. Previously listed and Endangered on Global IUCN Red List up to 2021, now listed as Least Concern. Still listed as Near Threatened on European Red List. This does not indicate 'business as usual' should resume. The only reason populations were able to recover was through strict quotas and management, this species is still at risk if these are lifted. Climate change may also affect this migratory species.

Action: Records of new sites for this species, with details of habitat and population are always valuable. Observations with a photograph can be recorded using iNaturalist, find the MBDP-NI iNaturalist project here.

Alternatively, records can be sent to CEDaR, National Museums Northern Ireland, 153 Bangor Road, Cultra, Holywood, County Down, BT18 0EU. Tel 028 9039 5257, e-mail cedar.records@nationalmuseumsni.org, or via the online portal.

Objectives:

• Monitor and maintain current population.
• Continue to enforce strict management to ensure continued recovery.
• Regularly reassess population and catch data and have a plan in place should these start to show any decline.

Conservation:

• Only a small number of skippers have been permitted by DAERA to target this species.
• Any targeted fishing is strictly limited to rod and reel only, with no chumming allowed.
• There is a strict catch and release policy in place in Northern Ireland.
• Listed as Near Threatened on European Red List.

Distribution Map from NBN: Thunnus thynnus at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Thunnus thynnus at iNaturalist World Species Observations database.

WoRMS: Thunnus thynnus at World Register of Marine Species. Accepted name: Thunnus thynnus (Linnaeus, 1758). AphiaID: 127029.

Classification: Biota; Animalia; Chordata; Vertebrata; Gnathostomata; Osteichthyes; Actinopterygii; Actinopteri; Teleostei; Scombriformes; Scombridae; Scombrinae; Thunnus