Now the clams aren't there as much as they used to be,'' said Bick, who's been digging clams for 15 years to feed himself and five sisters. They're not firm anymore. They're more liquid. In response, fish farmers point out they have been switching from antibiotics to vaccines, developing natural alternatives to laboratory-made pigments, and using sensors to judge when the fish are full so there will be less food waste. In Chile, they're even trying to breed fish that produce less waste, said Eugenio Larrain of Fundacion Chile, which oversees fish farms in the South American nation.
Efficiency can only go so far though.
Even if nothing artificial was put in the fish feed, it would still add nitrogen and phosphorous to the water, disrupting the natural balance, Soto said. But she tries to keep the waste and feed from salmon farms in perspective. In the lakes Soto has studied, salmon farms were responsible for 13 to 15 percent of the change in water quality. Erosion, logging and sewage from nearby towns had a much larger impact. The contamination from salmon farms can be managed, Soto said.