Scientists at the University of Hawaii’s Institute of Marine Biology have shown that tilapia injected with recombinant bovine growth hormone, or rBGH, grow to be nearly twice the size of control fish in four weeks. The four-year study, a collaborative effort by the University of Hawaii and University of California Sea Grant Programs, was partly funded by the Monsanto Company, which developed and patented the rBGH drug POSILAC.

According to lead scientist Gordon Grau, the study’s goal was merely to find out whether rBGH, injected into the fish, would promote its growth. “This growth hormone is not something that is going to be practical overnight,” Grau said, as quoted in California Sea Grant’s fall 2003 Sea Grant News. Research to develop a practical application method would require approval from the Food and Drug Administration (FDA), a time-consuming process. Sea Grant provided $100,000, and Monsanto a one-time unrestricted gift of $80,000 toward the project, according to Mary Donohue, associate director for Hawaii Sea Grant. Others at Sea Grant deferred questions about the research to Grau. Repeated efforts to reach him, however, were unsuccessful.

Tilapia growers have expressed cautious interest. “If proven safe, I think the industry would jump all over it,” said Mark Willows, marketing director of the North American Fish Farmers Cooperative. “It will take additional market research to determine demand for fish treated in this manner,” added Kevin Fitzsimmons of the American Tilapia Association.

Opponents of the FDA’s 1993 approval of rBGH to increase milk production in dairy cows, who continue to oppose the synthetic hormone’s use, voiced concerns. “It’s preliminary at this point, but this project raises many animal health, human health, and environmental questions,” said Joseph Mendelsohn, legal director of the nonprofit Center for Food Safety.

Popular Newcomer

Tilapia, a freshwater fish native to eastern Africa, is now the third most popular farmed food fish in the United States, after salmon and catfish. A mild-tasting white fish that can substitute for flounder and rockfish, it is marketed when about two pounds in weight. Between 1996 and 2002 the amount of tilapia sold annually in this country rose from 36,000 metric tons to 133,000 metric tons (live weight). In 2003, that amount climbed to an estimated 182,000 metric tons.
With wild-caught fish becoming scarce and consumers alarmed by recent reports of polychlorinated biphenyls (PCBs) in farmed salmon and mercury contamination in tuna and other wild species, demand for tilapia is expected to rise. The American Tilapia Association predicts that tilapia sales will continue to grow in this country from an estimated $269 million in 2003 to over $1 billion in 2010, and during the same period, from $2 billion to $4 billion worldwide, making tilapia the “most important aquaculture crop in this century.”

Monterey Bay Aquarium’s Seafood Watch, which discourages consumption of species that are overfished or that, like farmed salmon, have negative environmental impacts, recommends tilapia as a good low-impact source of protein. Unlike salmon, a carnivorous species, tilapia are fed mostly grains. Also unlike farmed salmon, which are raised in open coastal waters in net pens and cages, a method that causes nearshore pollution and risks escapes which can lead to genetic mixing with wild salmon, tilapia are farmed in isolated ponds, tanks, and raceways. In the United States, wastewater from these systems is used to irrigate field crops, the effluent serving as fertilizer.

BRETT WILKISON is interning with Coast & Ocean.