Breakthrough in Bluefin Tuna farming

Bluefin Tuna is disappearing from the sea. Demand keeps prices high - which means people will keep fishing Bluefin Tuna until there is none left. Obviously this is an unsustainable situation. In Cartagena, in southern Spain, scientists from the EU’s Selfdott research project are researching how to farm Bluefin Tuna. So every night in July they take a boat and go out to collect eggs from two cages containing 60 Bluefin Tuna.

Says Fernando de la Gándara, the coordinator of the project: “This project aims to make it possible to produce Bluefin Tuna in the same way as we already produce sea bream, sea bass, turbot and salmon: using aquaculture. But this doesn’t mean the end of the Bluefin Tuna fishing, aquaculture will be a complement of fishing.”

In Malta, the day starts very early for Robert Vassallo-Agius, a biologist at the Malta Aquaculture Research centre. He is also working on the Selfdott project. Every morning in July he goes to the Bluefin cages to look for eggs, but last year he wasn’t as lucky as his colleagues. There weren’t any eggs, so this year, he’s made some changes: “This year we brought the cages into a cove, into a small bay were we hoped to have less currents, but this year again we had few eggs compared to Spain probably because temperature didn’t rise quick enough. This year was a quite cold year for sea water temperature and during what we think is the best eggs-laying period for tuna in captivity, we had cold temperatures.”

Bluefin Tuna use light and temperature to know when to reproduce. They are also very sensitive to water-quality. But that’s not all. Robert Vassallo-Agius continues: “Bluefin Tuna poses another problem; it is a very big and delicate fish. So because of its size we can’t handle it, we can’t check it, we can’t see what maturation stage it is at, like we do with sea bream, for example. And for this reason it causes another problem which is logistics; how to collect the eggs.”

Harvesting even small quantities of farmed eggs is really hard because Bluefin Tuna need special care all year round. So these scientists are being helped by private companies that were working with tuna even before this project started.

Says Antonio Belmonte, a biologist at Caladeros del Mediterráneo: “We ensure that the fish have perfect living conditions. Also we ensure that every care is taken to avoid any kind of problem during the eggs-laying period.”

Some of these eggs stay in Spain, and others go to France, Greece and Israel. Scientists use them to learn how to produce a full-grown fish, which is the next step of this project. Germany, Italy and Norway are also taking part in the project.

Says Fernando de la Gándara: “There were fewer eggs being laid in Malta than here in Cartagena, but we have achieved the reproduction of Bluefin Tuna in captivity. So now that we have shown that is possible, the next hurdle is breeding Bluefin Tuna larvae, and that will require a special effort.”

The challenge is ensuring the survival of the larvae. Last year scientists managed to keep some of them alive for more than 70 days. Now they are hoping that some of them will grow to at least a kilo, which is really hard to achieve with Bluefin Tuna. There are all sorts of complex problems like stress and cannibalism, but they hope that with the right feeding, the problems will be solved.

Says Aurelio Ortega, another biologist, from the Instituto Español de Oceanografía: “Bluefin Tuna grows very fast. This is why tuna have very high nutritional requirements. It needs a lot of energy, much more than other species that we are farming. So we have to give them very high-energy food compared with the food that we give to sea bream or seabass, for example. But this is also a fish that lays eggs in salt water rather than fresh, so it needs very high quality water with high concentrations of oxygen.”

Scientists are optimistic about this project because in the past they have succeeded in breeding wild species in captivity.

Fernando de la Gándara: “Bonito, which belongs to the same family as Tuna, is smaller so it’s easier to handle and with this species we had a huge achievement: for the first time in the world we closed the biologic cycle of bonito in captivity. That means that we get fish in captivity from parents that were born also in captivity.”

In Malta, Robert’s team succeeded in breeding amberjack, which also fetched high prices on the open market. These achievements show the way for the Bluefin Tuna. It’s time to take them out of the sea. Robert Vassallo-Agius: “The immediate next step is to improve the larvae’s survival. But at the same time in parallel we have to run towards producing a land-based facility where Bluefin Tuna brood stock can be held in captivity, so they can bring eggs in a better way than they do in the cages.”

The land-based facility for Bluefin Tuna will look like the amberjack farm in Malta. Here, the light and the water temperature can be controlled, so that the fish live in ideal conditions for reproduction, which is crucial if farming them is to become a reality.

Fernando de la Gándara: “We know the origins of farmed fish, we know what we are eating, and this is traceability. We know everything about a farmed fish. Also, farmed fish are of standard quality, so consumers who buys it know exactly what they are buying.”

Scientists have also been holding a series of blind tastings: the results are surprising. 50% preferred the taste of wild tuna, and 50% prefer the taste of wild tuna. This is good news because the only way to supply markets with as much Bluefin Tuna as they want is via aquaculture, as it is done now with salmon or shell-fish.

Robert Vassallo-Agius: “With all the effort that are taking place now on Bluefin Tuna, with everybody’s input, and there are some very good experiments going on with the eggs that are now produced from Spain, I think we will have some progress and maybe there will be some tuna aquaculture production in the near, not so distant future.”

The hope is that farming Bluefin Tuna will take the pressure off wild stocks – allowing them to breed in peace so that Bluefin Tuna doesn’t disappear from our seas forever.