Research team studying tuna aquaculture in Mexico

As tuna ranching expands rapidly along Mexico’s Baja California peninsula on the Pacific coast, just below the U.S./Mexico border, a team of researchers from the United States and Mexico is undertaking a study of the industry.

The practice began in 1996 with just a couple of operations, but the favorable temperate climate and a lack of quota regulations led to rapid growth, according to the World Aquaculture Association.

Tuna aquaculture has not caught on in the U.S. because of regulatory restraints and conflicting uses of the coast.

As both production and demand increase, environmental and conservation concerns are growing, too.

Seeking best practices
Researchers Charles Yarish, professor of ecology and evolutionary biology at UConn, and Barry Costa-Pierce, director of Rhode Island Sea Grant and a professor of fisheries and aquaculture at the University of Rhode Island, are working with José Zertuche, a professor of oceanography at the Universidad Autónoma de Baja California, Ensenada, Mexico, and associates, to assess tuna and sardine stocks along the coasts of southern California, northwest Baja, and the Gulf of California.

The study is funded by the Packard Foundation.

The researchers are examining aquaculture practices and networks, and will evaluate governance and social issues associated with “capture-based” tuna ranching.

They hope to determine best practices and make recommendations regarding the methods needed to develop successful captive reproduction, feeds, and non-polluting systems for tuna farming.

Currently, fishing boats capture two-year-old tuna in nets as they swim along the coast offshore, tow them slowly toward the shore and enclose them in circular pens in inshore bays, then fatten them up with small fish such as sardines for several months before selling them.

“Mexican tuna operations are often incorrectly called ‘farms’ but should more appropriately be termed ‘ranches’,” says Yarish, because they use wild-caught fish for both stocks and feeds.

A true “farm” would be one in which fish are raised from egg to adult stages in captivity, likely using a closed-system aquaculture process, he says.

The fish would not be killed for market until an order was received, so they would stay fresh and could readily be shipped, for example, from Baja to Los Angeles to Tokyo.

The species currently marketed include predominantly the Pacific Bluefin tuna, Thunnus thynnus orientalis, which is prized by gourmets, but also smaller quantities of yellowfin and bigeye tuna.