Unlocking the secrets of bluefin tuna reproduction: a step-by-step with Fernando de la Gándara

We Are Aquaculture talked with Fernando de la Gándara, the director of the Spanish Institute of Oceanography (IEO) who, together with Aurelio Ortega and his team, achieved a worldwide milestone: closing the bluefin tuna breeding cycle on land. During the conversation, amid the excitement of the achievement, he told us the story of research that has been carried out for more than twenty years and has gone through land and sea to decipher one of the questions of aquaculture: how to make the bluefin tuna species for cultivation. 

An investigation was also carried out in the sea

The milestone of completing the tuna breeding cycle on land is worldwide. However, this research had been performed years ago, but in the sea, because Fernando explained, "We started this process almost 25 years ago."

De la Gándara explained that this milestone is another stage in the process. One that still has some things to be shaped but which is being built part by part from the foundations. 

"The first thing we did was to bring together all those interested in bluefin tuna, both farmed and fished, and we held a congress in 2002 funded by the European Union." A small step and approach to the subject that would begin to flourish a year later. 

Thus, following the success of the congress, in 2003, the European Union awarded them a project in which they demonstrated that bluefin tuna reproduction in captivity was possible. "In cages at that time," he points out, "and we proved it." 

However, it would not be the only time the EU had its eye on bluefin tuna and the IEO projects. In 2009, the Spanish institution presented another project, this time to raise juvenile tuna in captivity. Once again, they were successful. 

"Since then, we have been chaining several projects and always counting on the collaboration of the Ricardo Fuentes Group because we did not have the concession to have cages in the sea." 

Fernando began by briefly explaining to us how this project had been carried out throughout all these years with the hope that it was a hard road but full of small victories. One of those is that it was not the first time they achieved the biological closure of the species. By 2016, the milestone was completed, but in quite different conditions, in cages in the sea. 

The bittersweet feeling of getting what was expected but always remembering that nature has its own rules

We managed to produce tuna in captivity, we took these tuna to the cages, we bred them there, and that was when in June 2016 we had clutches of tuna that had been bred in captivity." However, everything would change in December of that same year. One of the strongest storms in Spain in living memory occurred, causing the cages to be destroyed, and they lost the tuna which they had managed to complete the cycle after six years of work. "The sea is the sea," explained de la Gándara. 

"The thing is that the work is lost, but the knowledge is not," he explained to We Are Aquaculture. At that moment, together with financial support from the European Union through the autonomous community of Murcia, they decided to build a land-based facility. This solved the previous problem and made it possible not only to house the tuna and control their reproduction, but to avoid the risks of a storm. 

Therefore, in 2015, they inaugurated the ICRA (Bluefin Tuna Spawning Stock Monitoring Facility) a facility of four large tanks, Fernando explained that "the largest is 22 meters in diameter and 10 meters deep." 

ICRA, whose purpose is what its name explains: to assist bluefin tuna reproduction. Hence, from the eggs supplied by the Ricardo Fuentes Group, they produced fry, which were then transported to the ICRA, where they have been for six years. 

After these years, Fernando explained that the tuna had grown a lot with the conditions provided, which differed significantly from the cages in the sea. "Right now, we have tuna that have reached six years of age and are over 300 kg… They are massive," explained de la Gándara. To clarify, the typical weight range for bluefin tuna is 220 to 250 kilograms. 

The discovery of the milestone, bluefin tuna spawning 

Tuna in the wild typically reproduce starting from the fourth year. While aquaculture endeavors to replicate these conditions, it isn't identical. Consequently, various techniques are employed depending on the species. But what method did the IEO use? When it comes to their success in captive reproduction, Fernando explained that they achieved it by utilizing hormones. 

"This is a technique that we developed in the cages because, in captivity, the final phase of reproduction is blocked, in particular by the stress that the tuna itself has in captivity." To reach this, the hormone GNBH used to deactivate these barriers that the tuna puts up. Nevertheless, throughout the evolution of the project and its different characteristics, it did not work the same way. 

"That worked very well in cages for us. Additionally, we devised a system to inject the hormone using an underwater harpoon and divers. Nevertheless, although it worked in cages, it did not in the tanks." But this was the year they finally achieved it. De la Gándara explained that perhaps the mistake they had made in previous years was the timing, being "too hasty" in hormone injection. "That's why this year we considered giving them more time, and from Thursday – which was the hormone injection – by Saturday, we already had the spawns." 

Undoubtedly, a decision that has yielded global-scale results, culminating in the milestone of this discovery. 

Bluefin tuna, the last great challenge for aquaculture 

"I always say that tuna is the last great challenge of marine aquaculture," de la Gándara began, explaining. "It is a big fish and one that reproduces when it is over 50 kg in weight. A fish that is used to living in the open sea without any obstacles." 

With these characteristics, it is already possible to imagine the complications of the study. "You can't manipulate it like other species. Tuna is as it is." In our discussion with Fernando at We Are Aquaculture, it became evident that while each species possesses its distinct characteristics, this one was truly exceptional. "If it had been easy, it would have been done already," said de la Gándara. 

The next step 

"We no longer rely on anyone for the eggs," Fernando began to explain to We Are Aquaculture, though they will continue to collaborate with Ricardo Fuentes. Nevertheless, he emphasized that there is still work to be done. "This is one of the phases, but we have a lot to improve." Among the examples he mentioned were the rearing of juveniles and enhancing their survival rate, among other factors. 

Thus, de la Gándara told us that it is not yet profitable in the short to medium term, but like any self-respecting discovery, it needs time to mature. 

For the moment, the first step after the discovery will be based on nutrition. However, the most important thing is that the research continues with the motivation of the first day, and as Fernando explains: "Every year we are improving." 

Certainly, as a significant step in the field of marine science and bluefin tuna aquaculture, Fernando, and the researchers at IEO are well aware that it is a recognition of their hard work. Still, there are many more steps to take before fully understanding how to make bluefin tuna a commercially viable aquaculture species.

About the Spanish Institute of Oceanography (IEO)

The Spanish Institute of Oceanography (IEO) established in 1914, is a public research institution under the Ministry of Science and Innovation and part of the Council for Scientific Research (CSIC). With a budget exceeding 65 million euros, IEO has a team of around 700 employees, primarily researchers. It conducts high-quality research in oceanography and marine sciences, advises the government on fisheries and marine policy. Furthermore, it represents Spain in international marine organizations, promotes regional and global marine research collaboration. The IEO's mission is to enhance the understanding of the oceans and promote their sustainable use.