St. Lawrence species

Atlantic bluefin tuna

Thunnus thynnus

Type of resource

  • Fish
  • Pelagic fish

Status of the resource

  • Endangered

In season

Fresh year round.

SIZE : 2 m, up to 3.1 m for 725 kg.

LIFE EXPECTANCY : From 20 to 50 years.


Spawning takes place in the Gulf of Mexico, between the months of April and June. Tuna tend to return to the same areas for reproduction.

Each female lays between 30 and 60 million small, transparent eggs directly into the water column, close to the surface. These planktonic eggs hatch in 2 or 3 days.

The Atlantic bluefin tuna is a large fish with a dark blue back. The color fades towards its belly, which is silvery. Its torpedo-shaped body is perfect for speed.

Its head ends in a pointed snout. The eyes are small.

On its back are two large fins, one of which is reddish-brown, followed by a series of small triangular outgrowths giving the back of the body a dented appearance. The tail is powerful and shaped like a crescent moon.

In the water column, usually between the surface and a depth of 100 m, but can reach depths of over 1,000 m.

The Atlantic bluefin tuna is a highly migratory species, which travels no less than 10,000 km per year. It can tolerate wide temperature variations, from 3 ° C to 30 ° C.

During the summer, it feeds in Canadian waters, including the Gulf of St. Lawrence; it spends the winter in the Gulf of Mexico. It regularly travels in shoals.

Atlantic bluefin tuna are highly migratory, traveling no less than 10,000 km a year.
Crédit : Sylvain Le Bris, photo taken in 2020.








Killer whales

Shortfin mako sharks


MACHINES : Line fishing, electric harpoon.


  • Quotas
  • Specified fishing season
  • Logbook to be updated for each fishing trip
  • Maximum number of 4 lines on the boat
  • Maximum number of 53 boats for the Quebec fleet and regulations on their size

Although the Atlantic bluefin tuna has been declared endangered due to over-fishing from the 1970s to the 1990s, its entry on the list of species protected by the Species at Risk Act has been rejected. This is due to the fact that its stock has shown a slight increase since the 2010s, even though its level remains very low compared to its historical levels.

Protection on all fronts

As bluefin tuna travel great distances, they can be found from one side of the Atlantic to the other. In 2022, the International Commission for the Conservation of Atlantic Tunas set up a new management procedure taking into account stocks on both the western and eastern sides (America and Europe). This should lead to more a more sustainable approach to fishing.

BENEFITS Atlantic bluefin tuna is rich in Omega-3 fatty acids, phosphorus, potassium, magnesium, and vitamins A and B12.

LET’S COOK Firm texture. Red flesh. Rich, flavorful taste.

It is not uncommon to speak of tuna “steak”, a reference to its meat-like texture and color.


  • When buying tuna, it is important to check its Latin name. Given its endangered status, we do not recommend eating it if it is Thunnus thynnus, which comes from the West Atlantic. It is best to consume East Atlantic tuna, be it in great moderation.

Blame it on sushi

The development of the tuna sushi and sashimi market in Japan in the 1980s is what led to the increase in fishing; but a little too much.