Tuna, the sad emblem of overfishing and ocean degradation

Tuna, the sad emblem of overfishing and ocean degradation

This fish consumes a lot of energy swimming: on average one third of its weight every 24 hours. However, a tuna can weigh up to 900 kilos, which is more than the weight of a horse. The largest specimens can measure 3 meters!

Note: size and weight depend on the species and geographical areas.

Tuna: a fish at the top of the food chain
Located at the top of the food chain, it has few known predators apart from the killer whale. Tuna is a voracious predator, which feeds mainly on small pelagic fish, anchovies, sardines, herring, sandeels, sprats, mackerel, but also on squids, shrimps and pelagic crabs.

The main species
Bluefin tuna
Emblematic of the Mediterranean and of overfishing, this species actually includes three species:

Northern bluefin tuna (Thunnus thynnus) or Atlantic bluefin tuna or Mediterranean bluefin tuna further south,
the Pacific bluefin tuna (Thunnus orientalis)
and the southern bluefin tuna (Thunnus maccoyii).
Threatened with extinction by overfishing over the last fifteen years, these fish have seen their stocks recover thanks to regional fishing quotas. Nevertheless, the International Union for Conservation of Nature (IUCN) warns that this improved health of bluefin tuna stocks is taking place in a context of global fragility of other species, such as sharks and rays.

In addition, the “sustainable fishing” label of the East Atlantic bluefin tuna stock by the MSC (Marine Stewardship Council) worries the NGOs, especially as this sustainable fishing is carried out by Japanese fisheries.

Tuna – Seine fishing, trawler nets
Seine fishing
Yellowfin tuna
With its tender and pinkish flesh, Thunnus albacares or yellowfin is increasingly fished. There is no minimum size of fishing, and its catches are not always duly declared, as it is sometimes declared as bigeye tuna. This fish weighing more than 200 kilos is the second most fished tuna species in the world, with almost two million tons per year.

Yellowfin tuna is mainly fished in :

the Pacific Ocean (60%),
then the Indian Ocean (30%)
and in the Atlantic Ocean (10%).
Yellowfin tuna can reach 200 kg and measure 2.50 m at maturity. It is a migratory species that can gather with other tunas in schools of the same size.

Schools of tuna
Albacore or white tuna
The albacore (Thunnus alalunga) is considered the most noble of the tunas, because of the fineness and firmness of its flesh. It is also the smallest, weighing on average about twenty kilos, exceptionally about forty kilos for 1.10m.

Except in the Indian Ocean, the management of albacore tuna fishing is considered sustainable.

This fish is mainly caught

in the Pacific Ocean (60%),
in the Atlantic Ocean (21%)
and the Indian Ocean (18%).
Catches are very low in the Mediterranean (1%).
Spain is the main fishing country for albacore. French production (9,228 tons in 2018, including French Polynesia) is very seasonal, with most of the landings recorded between the months of August and October, with French catches coming mainly from the North Atlantic stock.

Bigeye tuna, the canned tuna

As its name indicates, this is the largest of the tuna species. Its weakness is to live in bans, including other species. Consumed in cans and sashimi, the thunnus obesus or “patudo” is threatened with extinction by 2030.

Absent from the Mediterranean, bigeye tuna was, until now, mainly fished by Ecuador, which exploits the Pacific stocks. In Europe, half of this fish is caught as by-catch. But Japanese canned food and sashimi are now putting it to shame, caught at the juvenile stage.
It is caught mainly by seine. Its exploitation has been increasing everywhere for more than 50 years.

Tuna: the world’s leading fishery

With 5 million tons of tuna caught each year, it is the first fish caught in the world. It is also the first fish consumed in cans.

According to the IUCN, despite an overall improvement at the species level, many regional tuna stocks remain severely depleted. This is the case of the Pacific bluefin tuna, which has only 5% of its original biomass.

The IUCN also alerts on the lack of global management of the oceans in favor of a sustainable management of their resources. If the tuna is less affected regionally by the fishing quotas, its environment is deteriorating. Habitat degradation and global warming are now the two other pressures that weigh on this animal and, more globally, on all marine species.

A Japanese tradition
In Tokyo, the New Year tuna auction is a tradition. In 2022, a 211-kilogram specimen reached the princely sum of 129,000 euros, a modest bid compared to the record for the year 2019, with a 278-kilogram tuna for 2.7 million euros. Winning this auction brings good luck, and a lot of publicity for the acquiring restaurant owner.

A lucky charm in danger of extinction: if Japan has approved a recovery plan for bluefin tuna by 2034, it is reduced by 96%.