As a flock of seagulls swoops on a salmon farm in New Zealand's Marlborough Sounds, attracted by the thrashing fish within, tour boat operator Peter Beech sighs and says: "I'm not sure this is a fight we can win."
Beech has plied the pristine waters at the top of the South Island all his life but fears plans to increase aquaculture in the Sounds will create an ecological time bomb in the area his family has lived in for six generations.
The New Zealand government has announced the end of a 10-year moratorium on aquaculture in the region, a magnet for tourists who come to marvel at dolphins, seals and whales on eco-tours such as those operated by Beech.
"It has the potential to turn our beautiful Sounds into one great big fish farming area," he said.
The New Zealand King Salmon Company has applied to create more fish farms in the area to double its output to 15,000 tonnes by 2015 as part of a long-term plan to become an NZ$500 million ($410 million) company.
The debate puts the Marlborough Sounds at the centre of debate over whether fish farms can be sustainably developed in environmentally sensitive areas to meet booming world demand for seafood.
Aquaculture accounts for about 46 percent of the seafood consumed annually and the proportion is increasing as wild fish stocks decline, according to a UN Food and Agriculture Organisation report released this year.
The World Wildlife Fund says that, if properly managed, aquaculture has the potential to reduce pressure on wild fish stocks amid rising demand for seafood, particularly from increasingly affluent Asian consumers.
King Salmon says it is acutely aware of its environmental responsibility and there have been no problems at its existing Marlborough Sounds fish farms, which were established before the moratorium.
Chief executive Grant Rosewarne said expanding the industry would also bring much-needed jobs to the area and, with premium smoked salmon fetching up to NZ$250 a kilogram, provide export earnings for New Zealand's flagging economy.
"I don't think there's any other agricultural industry that in such a small amount of space can create such a huge amount of value," he told AFP at the company's processing factory in Nelson.
He points out that even if the expansion plan goes ahead, King Salmon's fish farms will cover only 15 hectares (37 acres) of Marlborough Sounds's waters, about 0.1 percent of its total area.
In addition he says that King Salmon's farms do not have pests such as sea lice that infect similar operations overseas and it is in the company's interests to keep it that way.
But Beech, who has established an environmental group called Guardians of the Sounds, points to the environmental problems created by salmon farms in countries like Scotland and Chile when the industry rapidly expanded.
"The only reason it hasn't happened here is because there are so few of them. But as soon as they start to farm intensively, they'll get diseased, you mark my words, just like they have in every other country in the world."
Beech said the "visual pollution" of fish farms - which are enclosed by large fences around the fish pools - and the threat of disease could undermine New Zealand's "100 percent pure" tourism marketing slogan.
Local farmer Eric Jorgensen, chair of another green group called SoundFish, said his main concern was that the government, with its eye on lucrative export dollars, had declared aquaculture an industry of national significance.
He said this meant responsibility for planning and approvals has been stripped from the regional council and given to the national government in Wellington, stoking fears it was intent on allowing a massive expansion.
The danger, Jorgensen, said, was that in its eagerness to increase aquaculture production, the government would allow in overseas players who did not have a commitment to preserving the Sounds' unique environment.
"There is a place for aquaculture. No problem with that. I don't think anyone today would say that there should be no aquaculture," he said.
"But (we need to determine) what is the optimum amount of aquaculture that can and should occur, without undermining all those other activities that are very important to the community and local businesses."