Revolutionizing tuna farming

To meet global demand for bluefin tuna while protecting the species, many seafood processors rely on fish farms. The major challenge in successfully rearing tuna lies in the fish feed. Together with the Japanese company Nissui, Bühler has developed a tuna feed that will enable sustainable, economic farming.

Tsuyoshi Goto is on board a fishing boat owned by Kaneko Sangyo, a group company of Nissui Cooperation, one of the largest Japanese seafood processors. It’s 9 a. m., and the ship is near Kabashima Island in the Sea of Japan, about 90 kilometers from the mainland. It’s feeding time.
The bluefin tuna are excited, swimming circles around the aquafarm. They know what is about to happen. They are fed three times a week in the spring. Goto-san (Japanese for Mr. Goto) bends down, reaches into the sack behind him, and takes out a handful of oblong pellets. They look like a mix of chocolate and energy bar, but they definitely smell fishy.
“This is the future of tuna farming,” he says, tossing the pellets into the 40-by-40-meter floating cage. This is the signal that feeding time is about to start. The handful of pellets is followed by a canon shot that blows one ton of feed into the cage. The tunas come. Nearly 1.2 meters long, the creatures stir the water, having at the energy bars.
Tsuyoshi Goto is Plant and Quality Manager at Farm Choice, a subsidiary of Nissui. Farm Choice produces feed for fish farming. Together with Bühler, his team developed these extruded pellets, the key to sustainable, economical tuna farming.

Around the islands of Japan there are 1600 aquafarming cages.

Bluefin tuna are endangered

Since the end of the 1990s, the population of blue-fin tuna maturing in the wild has decreased by 80 percent – an alarming trend. Yet, fish consumption has continued to grow for years. In 2016, 151 million tons of fish were consumed worldwide, corresponding to over 20 kilograms per capita.
Among the Japanese, fish takes the number one spot when it comes to most popular foods. On average, each Japanese citizen eats 66 kilograms a year, with this tendency growing. At the top of the menu – tuna. Of course, this is also related to the increasing popularity of sushi across the globe.
Demand for high-quality tuna has skyrocketed in recent years. The catch quotas set by the government are nowhere near enough to satisfy the hunger for sushi, resulting in illegal fishing. Many are unable to resist the appeal of earning a quick buck.
At Japanese fish markets, a fully grown 200-kilogram tuna can easily bring in tens of thousands of dollars, with the record price for a single fish coming in at 1.3 million dollars. In 2013, a sushi restaurant purchased this high-cost bluefin tuna at the prestigious New Year auction at the Tsukiji fish market in Tokyo. Naturally, this exorbitant price gained the media’s attention. One thing this development makes clear is that tuna has become a multi-billion dollar business. But the consequences are as obvious as they are alarming. Bluefin tuna has become an endangered species.

Bühler is the expert technology provider when it comes to fish feed production.

Tsuyoshi Goto, Plant and Quality Manager, Farm Choice

The huge sack filled with compound feed has done its job here and the crew makes their way to the next cage. In total, there are around 1,600 of them spread around the Japanese islands.
Kaneko, another subsidiary of the Nissui Cooperation and the link between Farm Choice as the feed producer and the Nissui brand, operates several farms in the Goto Island archipelago, no more than 20 kilometers from the harbor. In the morn-ing, Okuura is always the first stop – it’s where the large tunas can be found. At four-years-old and weighing in at 80 to 100 kilograms, they are “ready for harvesting,” as it is officially called. Kaneko manages the farms, is responsible for butchering the fish, and processes the tuna in several plants. The company sells cut-to-size pieces to sushi restaurants as well as end consumers around the world.
The concept of tuna farming is nothing new. Research in the area began as early as the 1970s, when it was first discovered that the population of bluefin tuna was declining while demand was growing. The research is now led by Japanese Kinki University. But Nissui also identified the trend in the ’90s, testing various methods and resulting in the establishment of Kaneko and Farm Choice. 

The right feed

The main problem in tuna farming is the survival rate. Less than 1 percent of fish eggs hatch into little tunas. By comparison, the survival rate of other farmed fish, for example salmon, is between 20 and 40 percent. And more important, of course, is that the few hatchlings quickly grow in terms of size and weight without major losses.
The issue: tuna are predators. If they aren’t fed enough or at all, or are given the wrong feed, they are no stranger to cannibalism and end up deplet-ing their own kind. On top of that, the bluefin tunas are very picky eaters and prefer to prey on herring and mackerels.
Past experiments with artificial feed failed miserably. Consistency, the mixing ratio, and shape were all too complex to produce and the tuna sim-ply did not accept them. The only remaining option was to eat fresh fish.
Consider this example: around 2,000 tuna are bred in a single cage. Each week, they need 40 tons of mackerels and herring. In total, the fish spend four years in a floating cage. Over time, this equates to 8,320 tons of fresh fish that are fed per unit and cycle. 8,320 tons! And there are over 1,600 cages like this in the Sea of Japan alone. This is not very efficient. However, it shows that the key issue lies in their feed.
Tuna farming may earn money despite the high costs associated with purchasing feed, but this is mainly due to the extremely high retail price of the fish.

This approach to production is far from sustainable. In parts of Japanese waters, even mackerels and herring are considered endangered species. There has to be another solution.

Tsuyoshi Goto, Farm Choice, and Nobuyuki Komiya, Bühler Japan, on a feeding tour

Collaboration with Bühler

“In 2010, we decided to collaborate with Bühler. Bühler is the expert technology provider when it comes to fish feed production. For us, it was clear that we could come a long way with their expertise in extrusion,” says Goto-san.
It is now evening. Goto-san has joined his colleagues for dinner, including Urs Wüst, Key Account Manager and fish-feed expert at Bühler. Having lived in Japan for 11 years, he is familiar with the culture and customs, and now provides Nissui with support on behalf of Bühler.
What else is on the table other than sushi – a fitting meal after a day at sea. Of course, bluefin tuna is also a must, sliced as sashimi or formed into a nigiri with wasabi and rice. What’s special about all this? The tuna served comes from one of the Kaneko fish farms. Fed exclusively with compound feed, produced on Bühler extruders.
Shortly after establishing contact in 2010, Goto-san and his team traveled to Switzerland to work with Bühler on the tuna feed production process. The main difficulties lie in the shape, composition, and different consistencies required for the feed. The shell of the pellets has to be both solid and soft, yet pliable, while the inside has to be soft, but not liquid. This recipe calls for the Swiss experts.
The lower the portion of fishmeal, the more sustainable and cost-effective the feed. “It contains all the ingredients that tuna need to grow: fishmeal, fish oil, vitamins, and minerals. Our feed enables healthy farming of tuna, without using antibiotics,” says Goto-san. After two years of intense collaboration, the pilot phase can begin. In 2012, Bühler installed three extruder lines in the Farm Choice production hall farm in Karatsu.

Developing the feed

In addition to the standard feed with mackerel and herring, several units are also fed with the extruded compound feed. Thanks to the higher nutritional value compared to fresh fish, a much lower amount is required. In addition to the standard feed with mackerel and herring, several units are also fed with the extruded compound feed. 

Three times a week, the up to 1.2-meter-long and 100-kilogram heavy tuna are fed.

Thanks to the higher nutritional value compared to fresh fish, a much lower amount is required. Instead of the standard 40 tons per week across five feeding days in spring, now only three feedings of 4.5 tons are necessary a week, a total of 13 tons. This saves time, personnel, and above all, costs for boats and fuel. And the pellets are also easier to store.
Unused feed can be put back and used at a later point in time. Yet another advantage over fresh fish, which has to be caught, portioned, frozen, transported, and finally thawed before the tuna can chow down. During the test phase, the feed is optimized in close collaboration with Bühler.

With underwater cameras in aquafarms, Goto-san studies the behavior of the fish during feeding. His team observes that the tuna hesitate before eating the pellets. Compared with real fish, the feed doesn’t have a “front.” Predators always eat their prey head first, as this makes them easier to swallow due to the direction of their scales and fins. As for the pellet, the tuna is unable to detect a head, which is cause for confusion. “So we changed the shape of the feed yet again. It was important to develop a kind of a point, sort of like a nose, to signalize to the tuna that this is the front,” explains Goto-san.
Minor adjustment, major success. The fish accept the feed. This recipe forms the basis for further experiments, with the objective of continuing to reduce the fishmeal content by 50 percent. The lower this portion, the cheaper and above all more sustainable production becomes.

Our feed enables healthy farming of tuna, without using antibiotics.

Tsuyoshi Goto, Plant and Quality Manager, Farm Choice

A toast to success

Tsuyoshi Goto, his team, and Urs Wüst have just reached the sake. This rice wine goes perfectly with sushi. “I am confident that we will meet our goal. Tuna farming will turn into a huge business. Of course, it’s a risk, but I am certain that we will continue on our course for success,” says Wüst. But first, another toast to their success.

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