Cornwall Good Seafood Guide logo

Atlantic bluefin tuna

When is best to eat?

J
F
M
A
M
J
J
A
S✔
O✔
N✔
D✔
Atlantic bluefin tuna

Description

The Atlantic bluefin Tuna, Thunnus thynnus, is a giant of the fish world growing to a maximum size of 3 meters and weighing up to 250 kilos. These torpedo shaped fish are built for speed and power and travel huge distances in the open ocean. Unlike most fish they are warm blooded with heat generated in their powerful swimming muscles that enable them to accelerate rapidly, and gives them improved cognitive power and reactions. They are incredible predators and are at the top of the oceanic food chain.    

 

Sustainability Overview

Atlantic bluefin tuna are a fast simming and wide ranging species that has always occasionally ventured into UK waters but they became an extremely rare sight through the latter half of the 20th century when this higly valuable species was fished near to extinction. Thanks to improved international management stocks appear to have recovered.  Bluefin tuna appear in Cornish waters in mid-summer and are seen well into autumn. From 2021 the UK  have had a small quota of blue fin tuna meaning that it is now legal for licenced fishermen to land them for human consumption. A stritcly monitored and limited line caught fishery has been created and at present line caught fish is the best option in terms of sustainablity. We hope that this newly opened fishery continues to be well managed and rules, both locally and internationally are strictly enforced as this is a top predator that is very easily over-fished and has only recently recovered from the brink of near extinction.

Best choice is line caught tuna, always check it was caught by a licenced fisher.

In 2021, 1.3 tonnes of Atlantic Bluefin tuna was landed to Cornish ports with a value of over £4000.

Updated April 2024

Sustainability ratings for this species

Hook and line

Cornwall

A commercial hook and line fishery for Atlantic bluefin tuna was opened in 2023. Number of boats are limited and a strict quota prevents overfishing.

Learn more

Ring Netting

Cornish waters

Commercial fishers who accidentally catch Atlantic bluefin tuna are allowed to land one fish per boat per day under new rules from MMO 2021

Learn more

Demersal Trawl

Cornish Waters

Commercial fishers who accidentally catch Atlantic bluefin tuna are allowed to land one fish per boat per day under new rules from MMO 2021

Learn more

Gill Netting

Cornish Waters

Commercial fishers who accidentally catch Atlantic bluefin tuna are allowed to land one fish per boat per day under new rules from MMO 2021

Learn more

How we rate fish

Cornwall Good Seafood Guide rates fish on sustainability using a scale of 1 to 5.

1, 2 and 3 are recommended, Fish to avoid are rated 5.

We use the system devised by the Marine Conservation Society (MCS) so our scores are comparable with the scores produced by MCS for the UK and fisheries from all around the world. For more information on scoring click here.

Biology

Tuna belong to the mackerel family, Scombridae. They are large, oceanic fish and are seasonally migratory, some making trans-oceanic journeys. Able to tolerate both warm and cool temperatures, bluefin tuna range throughout the entire north Atlantic and adjacent seas, (primarily the Mediterranean Sea) and can frequent depths to 1000m. Despite this thermal tolerance, a recent analysis of present vs. historical ranges concluded that Atlantic bluefin tuna has shown range contractions of 46% since 1960 - more than any other pelagic species . Despite poorly understood movements from east to west, a distinction in populations is made between the two regions. Interestingly, life history characteristics differ greatly between them. In the Mediterranean, bluefin tuna is assumed to mature at approximately 25 kg (age 4), whereas in the Gulf of Mexico in the West Atlantic, maturity occurs at approximately 145 kg (age 9). Northern bluefin grow slowly compared with other tunas and billfish but can reach more than 450cm in length and 680kg in weight with a maximum age of approximately 40 years. Spawning occurs from April to June in the Gulf of Mexico and June to August in the Mediterranean.

Stock Info

Atlantic bluefin tuna began reappearing in UK coastal waters in 2014 and since then they have been regularly sighted in increasing numbers around the coasts of Cornwall, and further along the south coast into Devon and Dorset waters.  The return of this incredible species is most likely due to the increase in their prey in our waters, small pelagic fish such as sardines. 
 
There are two stocks of Atlantic bluefin tuna: West Atlantic (western stock), and East Atlantic and Mediterranean (eastern stock). This rating is for the eastern stock. There has been a lot of uncertainty about the size and health of the Atlantic bluefin stock, and while it has recently improved, it is not clear whether it has reached sustainable levels. MCS considers there to be concern for the biomass, because it is recovering from an historically low level. The stock is not thought to be subject to overfishing, and so there is no concern for fishing pressure.
 
Atlantic bluefin tuna are assessed and managed by the International Commission for the Conservation of Atlantic Tunas (ICCAT). The eastern stock was heavily fished from the 1950s until 1996, after which, catch limits and a limit in the size of tuna that could be taken caused catches to drop from 60,000 tonnes to 10,00 tonnes.
The stock declined from the 1970s until 1991, staying at a low level and coming close to stock collapse until it began to increase in the mid-2000s. A new stock assessment was produced in 2020 but depends on recruitment estimates, which are highly unstable, and is also closely related to assumptions made about stock structure and migratory behaviour, which are poorly known. Nonetheless, compared to 2017, the extra data now available confirm a recent stock biomass increase, although the magnitude of the increase remains difficult to quantify. Fishing pressure appears to be clearly below the target level of F0.1, which is a proxy for FMSY and has been set with the aim of maintaining the biomass at B0.1 (BMSY). The average fishing pressure from 2015-2017 is 42.6% of the target level, indicating that overfishing is not taking place. Given the levels of uncertainty, and that the stock is recovering from very low levels, MCS considers that there is still concern for the biomass. The stock is not thought to be subject to overfishing, and so there is no concern for fishing pressure.
 
Projections on the future of the stock could not be made owing to the uncertainty in the data. However, an analysis of the effect of the current and future catch limits (32,240t in 2019 and 36,000 t in 2020-2022) suggests that there is no cause to change them. The projections from the 2017 advice have been reiterated in the 2020 assessment: a constant catch of 36,000 tons from 2018 onwards would keep fishing pressure below the target level with a probability higher than 60% in 2021 and in 2022.
 
The introduction of fattening and farming activities into the Mediterranean in 1997 and good market conditions resulted in rapid changes in the Mediterranean fisheries for bluefin tuna, mainly due to increasing but unknown catches of juveniles going into farms. There have been considerable improvements in data quality and quantity over the past few years but important gaps remain in the temporal and spatial coverage for detailed size and catch-effort statistics for several fisheries, especially in the Mediterranean before the implementation of stereo video cameras in farms in 2014. It still remains unclear how much of the Eastern Atlantic stock mixes with and supports the Western Atlantic stock.
 
 
In 2021 the IUCN changed the status of Atlantic bluefin tuna from Critically endangered to Least concern. Read more here.
 
 
 

Management

Tuna, marlin, and swordfish are highly migratory species, found on the high seas and in numerous countries' waters. This makes harmonised and effective management challenging. Regional Fisheries Management Organisations (RFMOs) are responsible for monitoring and managing these stocks on behalf of the countries that access them. However, the degree to which management is implemented, monitored and enforced by each country varies significantly.
 
Atlantic bluefin tuna is managed and assessed by the International Commission for the Conservation of Atlantic Tunas (ICCAT). After the eastern stock came close to collapse in the early 2000s, a rebuilding plan was introduced. It ran from 2007-2017, and included catch reductions and increases in minimum landing size. Although it is not known if the stock has reached target levels (Biomass at levels associated with Maximum Sustainable Yield), fishing pressure (F) was brought below FMSY. These measures are thought to have contributed to the subsequent rapid stock increase.
 
In 2021 a small quota for Atlantic bluefin tuna of 65 tonnes was allocated to the UK government. This quota was used in 2021 to open up a catch and release tagging sport fishery which is strictly licenced and controlled with only 15 licences issued in 2021 (see CHART website). Mortalities are to be avoided but any unitentional mortalities will have to be reported and the fish will be landed for research purposes and given to the MMO. (for more info visit government page)
 
In 2023 a Commercial hook and line fishery for Atlantic bluefin tuna was opened by the MMO as a trial small scale fishery, and the first targetted fishery for Atlantic Bluefin Tuna in recent times. This is a selective fishing method, with low risk of damage to seabed or to non target species, all fish caught have to be reported and are inspected by MMO, and data collected will be used to build information on tuna stocks in UK waters. The hook and line fishery is allocated 39 tonnes and was split between 10 vessels in 2023, who did not catch the full quota. The MMO have released their plan for Atlantic Bluefin Tuna fishing in 2024, which includes an increase to 13 vessels with hope to fullfil the allowance.
 
Recreational fishing for tuna withouth a permit is illegal. Any incidental catch must not be brought onto the vessel, it must be released alive, unharmed to the greatest extent possible. Recreational sea anglers must not land bluefin tuna. The MMO must be informed of any accidental mortality and they may request the fish to be landed to them for research purposes. From summer 2024, the MMO are launching a catch and release recreational fishery (CRRF) with a limit of 16 tonnes to restrict the level of effort from the recreational sector. Permit conditions are likely to stipulate that any BFT caught must not be harmed, removed from the sea, brought on board, or landed. However, training and codes of practice for BFT handling is expected to be voluntary, which if not followed could lead to accidental deaths.
 
The remainder of the 66 tonnes is allocated to bycaught Atlantic bluefin tuna by commercial fishers  using ring nets, gill nets or trawls. They can be landed as long as they are above the Minimum conservation reference size (30kg or 115cm fork length) and can then be sold for human consumption. Only one fish per commercial boat can be landed per day.
 
There is serious concern that these rules may not be enforced adequetly and that some recreational and commercial fishers may be tempted to illegally land tuna. Always be careful if buying tuna to ensure you know it was caught legally.
 
 
 
 

 

Capture Info

A commercial Bluefin Tuna hook and line trial fishery was opened in 2023 by the MMO -10 licences have been issued to UK commercial vessels who have a limited quota of 39 tonnes per year. Line fishing for tuna is selective and rarely harms other species and has no impact on the seabed. 
 
Commercial fishers using ring nets (purse seine nets), gill nets or trawls are not allowed to target bluefin tuna but if they accidentally catch them they are permitted to land one fish per vessel per day. 
 
The fish can only be landed if they are above the Minimum size of 30kg or 115cm fork length, and can only be caught using ring nets, demersal trawls, gill nets pelagic trawls and seine nets. More details are published here.
 

 

References

Atlantic Bluefin Tuna fishing plan 2024

Bluefin tuna in the UK, Information on the current rules applicable to Bluefin tuna in UK waters. MMO 

Bluefin tuna commercial trial fishery 2023 MMO

CHART - CEFAS Scientific Catch And Release sport fishery

Bluefin Tuna in the UK    Gov.uk

IUCN Red List Atlantic bluefin tuna

MMO landings data to Cornish ports.

ICCAT Stock Assessment 2022-23

ICCAT Multi-annual Management Plan Recommendation 2022

Where to buy

Find and buy Cornish Seafood

Sustainable alternatives

Cornish Sardine by Sarah McCartney

Cornish Sardine

Sardinus pilchardus

Hake by Sarah McCartney

Hake

Merluccius merluccius

mackerel by Sarah McCartney

Mackerel

Scomber scombrus

Sustainable alternative recipes

How to cook a crab

Read more

Soused Cornish sardines

Read more

How to prepare oysters

Read more

Crispy Fried Squid with Thai dipping sauce

Read more

Our Sponsors

Newsletter sign up

Keep up to date with the project by signing up for our newsletter.

Business Membership

How you can help

Donate

Get in touch

Cornwall Good Seafood Guide
Cornwall Wildlife Trust
Five Acres, Allet
Truro, Cornwall, TR4 9DJ

+44 (0) 1872 302251 seafood@cornwallwildlifetrust.org.uk

Cornwall Good Seafood Guide is underpinned by the Marine Conservation Society (MCS) Good Fish Guide. The first UK consumer guide to sustainable seafood. For more information visit www.fishonline.org

Website by Dewsign. Dewsign pro bono client