Both groups say the plant will cause irreparable damage to the ecosystem, seen as having tourism potential.

"Installing an aluminum reduction plant in Aysen will have devastating consequences for the Chilean salmon farming industry," Victor Hugo Puchi, president of the Salmon and Trout Producers Association, told reporters at a news conference.

Solid and liquid waste, air pollution and the noise level of the plant would all harm the salmon, which are raised in pens in nearby bays, he said.

The salmon farmers said they would present their complaint to Chilean environmental authorities and may take legal action.

Noranda's project, called Alumysa, would produce 440,000 tonnes of aluminum annually and involve construction of three hydro-electric dams and a port facility.

Alumysa Chief Executive Robert Biehl called the salmon producers' arguments "unacceptable" and accused them of lax environmental standards themselves.

He said the multinational would impose strict environmental controls over the entire affected region, which would likely force other industries in the area to adopt similar standards.

"We believe that the reason the salmon industry is so concerned is because currently a high level of environmental control does not exist and the serious inadequacies of the salmon industry in that respect are widely known," he said in a written statement.

Biehl said Noranda's environmental impact study meets Chilean and international standards and will create 8,000 jobs during its five-year construction.