New, Offshore Aquaculture Technique Aids Sustainability

When one-fifth of the world depends on fish as a food source, it cannot afford the consequences of overfishing. According to the United Nations Environment Programme, fishing is central to the livelihood and food security of 200 million people, especially in the developing world. Additionally, the Food and Agriculture Organization has reported more than 70 percent of the world’s fish species are overfished, fully exploited, or already depleted.

Aquaculture is currently responsible for more than 30 percent of the total world fishery production. It is continuing to grow at more than 10 percent per year and is entirely reshaping the fishery industry and management strategies worldwide. It is a new way to feed the world.

Rosenstiel School’s aquaculture program is spearheading research and development in the emerging fields of hatchery technology and offshore aquaculture. The program focuses on sustainability issues and is driven by the scientific and technological needs of industry as well as governmental, non-governmental organization, and the general public’s environmental and regulatory concerns. Rosenstiel School researchers have been successfully addressing controversial issues throughout all stages of fish farming, from egg to market.

The set-up
Rosenstiel School technology is for native species only and doesn’t use genetically modified organisms. Instead of antibiotics and drugs, it uses probiotics. This improves feeding efficiencies through high-quality feeds and optimized farming management practices. (Project data show that modern offshore aquaculture is 3.7 times more efficient than nature in transforming small fish such as menhaden into larger carnivorous fish such as cobia for human consumption.) The scientists are working with feed companies to develop environmentally friendly aquafeeds to dispense with fish meal. They are testing and using advanced methods and equipment that can withstand the elements and be used in unprotected areas offshore. And, they are constantly monitoring environmental impact and exploring ways to improve upon this approach.

Rosenstiel School’s aquaculture program, with the University of Puerto Rico and in partnership with the Bahamas and private industry, has developed offshore demonstration projects that are completely submerged in the deep waters. Due to greater depths and stronger currents, this open-sea approach disperses the organic and inorganic material typically associated with aquaculture. Also, with this approach, marine organisms consume the feed that filters outside the submerged fish cages.

So far, the Rosenstiel School and its partners have established offshore aquaculture farms at Culebra Island, Puerto Rico, and South Eleuthera, Bahamas. Enormous diamond-shaped cages sit at least 40 feet below the ocean’s surface to avoid being damaged by passing boats. The spaceship-like housings extend downward another 80-100 feet with a steady current of water flowing downstream through the cages to disperse byproducts downstream. These cages have been stocked with slow-growing mutton snapper or quick-growing cobia. Environmental data from the project indicate that this approach is effective in preventing impact on the surrounding environment.

The future
Remarkably, cobia growth rates in the offshore farms are among the fastest ever recorded, suggesting its success in producing a lot of fish with low environmental impact. The research, however, is not complete. Environmental assessments continue, as do ways to address new challenges that arise, such as predatory sharks or tropical storms. (South Eleuthera weathered category-4 Hurricane Frances in 2004 with no cage damage nor fish mortality.)

With the help of private enterprise partners, fish from the offshore pens are already being put to the ultimate test—that of consumer palates. Snapperfarm Inc. and AquaSense LLC are distributing limited quantities of all-natural mutton snapper and cobia to restaurants and fishmongers and paving the way for clean, economical aquaculture operations in the United States and Caribbean.

For more information, contact:
Barbra Gonzalez, Communications Director
Rosenstiel School of Marine and Atmospheric Science
305.421.4704 • barbgo@rsmas.miami.edu

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