Features
Taming bluefin tuna farming

Located in Puerto de Mazarrón in the southeast of Spain, the Infrastructure for Atlantic Bluefin Tuna Aquaculture, abbreviated as ICAR in Spanish, is approximately 70 km south of the city of Murcia. This facility is one of the five land-based farms owned by the Spanish Institute of Oceanography (Instituto Español de Oceanografía or IEO) in the country.

Construction of this facility began in 2011 and was finally completed in 2015, with an investment of nearly €6 million (US$6.3 million). As the IEO is dependent on the Ministry of Science and Innovation of Spain, this facility is 100 per cent publicly owned and is intended to generate knowledge about the breeding of Atlantic bluefin tuna (Thunnus thynnus) in captivity.

Highly prized as a food fish, especially for sushi and sashimi, bluefin tuna is one of the world’s most lucrative commercial fisheries. This situation may explain the severe overfishing this species faces and the importance of the farming techniques being developed here.

The facility

This research centre has an installed capacity of 7,000 m³ for tuna farming, divided into just four tanks: two for breeders, measuring 3,500 m³ (10m deep with a 22m diameter) and 2,600 m³ (9m deep with a 20m diameter); and two smaller tanks intended for juveniles, with capacities of 1,000 m³ (5.5m deep with a 14m diameter) and 300 m³ (three metres deep with an eight metres diameter).

The water supply is obtained from the sea through a nearby desalination plant before entering the ICAR premises. Due to its high quality, it is treated using only backwash disk filters before being incorporated into their Recirculation Aquaculture System (RAS). This RAS includes mechanical, biological, and chemical filters, as well as a skimmer and UV filters.

Other species, including sea bass (Dicentrarchus labrax), sea bream (Sparus aurata), greater amberjack (Seriola dumerili), dover sole (Solea solea), Atlantic wreckfish (Polyprion americanus), and Blackspot seabream (Pagellus bogaraveo), are also reared in this facility for research purposes. However, one of the most widely publicized recent achievements at this farm was the first worldwide on-land reproduction of bluefin tuna (see sidebar). About 10 people work here permanently.

Objectives and challenges

Over the past 20 years, most of the ICAR’s operations have involved catching wild adults and subsequently using them as breeders. The resulting fingerlings were then raised at their land-based farm until they reached 5-10g in weight, after which they were transferred to sea cages in several consortiums they participated in with private companies.

Once the farm became fully operational, the research team started farming and maintaining those fingerlings until they reached adult size in tanks. These individuals have ultimately become their first breeders that have never lived in the wild. Despite their success in closing the life cycle of this species, the researchers at ICAR still face significant challenges.

Aurelio Ortega, Chief of the Aquaculture Department at ICAR, believes that working with tuna is still very difficult. “The mortality rates are extremely high. From the larval stage until first feeding, we can face mortalities of 97-98 per cent, with a survival rate of only four per cent in the most favourable case, and very often between one to two per cent,” he explained.

“Besides, their way of dealing with any source of stress is to swim very fast when at sea, where nothing happens to them. Here, if they swim very fast and don’t have a perfect perception of the tank wall, they crash into the wall and die, or collide with each other when they are eating. We have that problem, which is more frequent in fish born in captivity than in wild individuals,” he added.

Future developments

Among other future research areas, the scientists at ICAR emphasize the importance of improving spawning results and feed consumption in larval stages, reducing mortality rates before grow-out, and eventually developing a genetic program.

“We have had some successful spawnings, but not as many as we would have wanted. Figures have improved compared to last year, and we have some ideas about where the problem may lie. These are animals that require a lot of tranquility, a perfect diet, low farming density, good water quality, etc.,” Aurelio Ortega said.

Regarding pre-fattening, these Spanish researchers have a project aimed at determining all the causes of mortality that occur while also focusing on the quality of the fingerlings produced.

“Establishing a genetic program is going to be challenging, but it’s something we want to pursue. We may have to work differently than with other species, as we cannot have several tanks involved due to the large size of these fish. We may need to rely on genetic studies of the offspring to determine their parentage, but it’s one of the lines of work we want to pursue,” he added.

Technology transfer

Since the participation of the IEO in the European project ‘Domestication of Thunnus thynnus’ (DOTT) and its subsequent projects, the researchers at ICAR have collaborated with numerous private companies, such as the Ricardo Fuentes Group, Malta Sea Farming, and Piscifactorías Albaladejo. These initiatives recorded the first breeding of bluefin tuna in captivity and the production of 14,000 juveniles intended for grow-out, among other achievements.

“We are now collaborating with a company from Cape Verde and supporting a Swiss firm that wants to set up here in Spain. Our results and knowledge are improving every day, and these companies want to be pioneers and be prepared to become the first to industrially produce bluefin tuna from juveniles born in captivity. However, we are not yet at the point where this technology allows for industrial-scale bluefin tuna farming,” Aurelio Ortega concluded. 

Eighteen-day-old fingerling of bluefin tuna. Photos: Spanish Institute of Oceanography).

THE FIRST LAND-BASED BLUEFIN TUNA BREEDING WORLDWIDE

The ICAR research team bred bluefin tuna in captivity for the first time in 2016, although this milestone was achieved in sea cages. Later that year, a very strong storm destroyed those cages, forcing the researchers to start the process again the following year. Twenty-five fish, each weighing about 150 kilograms, remain from those individuals hatched in 2017. Combined with eight adults born in 2018, they complete the breeder stocks at the facility.

On July 15, some of these breeders started spawning at ICAR, establishing a new breakthrough with this species: the reproduction of bluefin tuna in a land-based farm.