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Currents of dissent: critics say that farms in deep water could create ‘dead zones’. Credit: NOAA

Scientists and activists have criticized proposed legislation that would push US fish farms into deep waters, beyond the reach of states' environmental controls.

The bill, introduced on 7 June in the Senate, would allow aquaculture pens between 5.5 and 370 kilometres off the US coast. Federal laws, not state regulations, prevail in this ‘exclusive economic zone’ (EEZ). The United States has the largest EEZ in the world, encompassing about 9 million square kilometres.

Tuna, salmon, halibut and cod could be farmed in the EEZ. The National Oceanic and Atmospheric Administration (NOAA), which drew up the bill, argues that it would create an industry to produce healthy food in an environmentally friendly manner. But others say that deep-sea fish farms could transmit diseases to wild fish and pollute the waters.

Fisheries officials foresee annual fish production worth $5 billion. But this could produce as much nitrogen as 10 million pigs on land, according to the advocacy group Environmental Defense, based in New York City.

Nitrogen pollution can create ‘dead zones’ where few aquatic organisms live. “This can change the biology of the ocean,” says Roz Naylor, an economist at Stanford University, California, who studies aquaculture.

If the bill becomes law, it could also lead to a stand-off between state and federal authorities. Governors would be able to veto aquaculture in waters next to their state. Alaska's governor, Frank Murkowski, has already asked for a five-year moratorium so that more research can be done on the environmental and socioeconomic effects of aquaculture.

Environmentalists advocate more federal controls similar to the state ones proposed in a bill now going through the Californian legislature. The bill, sponsored by state senator Joe Simitian of Palo Alto, would set environmental standards for fish farms in state-controlled waters.

Many observers believe such guidelines are needed. Peter Douglas, executive director of the California Coastal Commission, served on a NOAA scientific advisory panel several years ago that recommended environmental guidelines for fish farms in the EEZ. “As far as I can tell, they blew those off,” says Douglas.

NOAA officials say they will address the issue of environmental standards during the upcoming discussions, and point out that they have done extensive background work. “This bill is ten years in the making,” says Michael Rubino, an economist with NOAA.

The federal bill is being sponsored in the Senate by Democrat Daniel Inouye of Hawaii, where limited fish farming is under way in state waters, and Republican Ted Stevens of Alaska, a state that prohibits aquaculture altogether.