Pioneering Soy-Based Tuna Feed

Featured in the July 2017 issue of our magazine.

“Tunas are the athletes of the sea, and the most profitable form of aquaculture today.”

That’s how Alejandro Buentello of Ichthus Unlimited describes tuna species, one of the most sought-after seafoods in the world. Buentello led the recent Illinois Soybean Association (ISA) checkoff program research project to incorporate soy into tuna feed, documented in the YouTube video, Feeding Bluefin.

He has seen how high global demand increases tuna value, and subsequently induces fishermen to over-fish wild stocks. But now the tuna industry is improving sustainability through ranching — catching and raising juvenile fish to market weight under a quota system – and developing hatchery technology to raise tuna from eggs.

“Closed-cycle aquaculture combined with sustainable diets offer the best opportunity to prevent wild tuna stocks depletion while meeting global demand,” he says. “But we have much to learn.”

As endurance athletes with a high activity level, tuna need a high-quality diet. Tuna ranching uses enormous quantities of wild-caught baitfish like sardines, squid or mackerel, and Buentello says prolonged feeding on these diets does not meet metabolic and nutrient demands of the high-performing fish. It also is one of the least sustainable, most costly elements of tuna production.

“Aquaculture has been working for years to replace fishmeal with plant feedstuffs to improve environmental and economic sustainability,” says Mark Albertson, ISA strategic market development director. “Soy protein is a complete protein that replaces fishmeal in diets for many aquatic species and has become the top ingredient in aquaculture feed. But limited alternative protein research exists for tuna because of their complexity.”

The ISA checkoff-funded research shows promise for addressing the tuna feed challenge. Three trials within the project tested various soy-based diets, and Buentello believes the results lay a platform to develop commercially manufactured tuna feed:

  • LARVAL ATLANTIC BLUEFIN PRODUCTION IN SPAIN. In the first trials of closed-loop cultivation for this tuna species, Buentello’s soy-based formulation improved larvae survival rates by at least 30 percent compared to other diets.
  • JUVENILE YELLOWFIN TESTING IN PANAMA. Young tuna tested various diet delivery formulations, including moist pellets, cooked sausages and extruded pellets, in a land-based trial. They accepted moist pellets best in the transition away from baitfish.
  • COMMERCIAL PACIFIC BLUEFIN FEEDING IN MEXICO: Off the northwest coast, ranched tuna in ocean net pens successfully transitioned to moist pellets. The soy-based diet decreased the feed conversion ratio from 28:1 to 4:1, and decreased fishmeal and fish oil use in the feed by tenfold.

“Our successful results demonstrate the potential for formulated feed in tuna aquaculture,” Buentello says. “The soy-based diet is more nutritionally dense, improving feed conversion ratio. Because of that, it’s projected to be almost twice as economical as baitfish.”