Waste on the Ocean Floor
Often described as a flow-through feedlot, the industrial open net-cages used to farm salmon rely on the “free services” of ocean currents to ‘clean up’ their waste. This practice impacts the ecosystem and the future of coastal communities who live near these farms.
According to industry sources, a typical BC salmon farm holds 720,000 fish with an average weight of 5 kg when they reach market size. The combined biomass of all those fish is equal to 360 Indian bull elephants.
On a provincial scale, 78,000 metric tonnes of farmed salmon went to market from BC salmon farms in 2006. Visualized in terms of elephants, that’s 15,600 Indian bull elephants – more than the entire elephant population in India.
The waste from all of these fish can build up under the pens smothering portions of the ocean bottom, contaminating the marine ecosystem and depriving species of oxygen. Or the bulk of waste may be carried away from the farm site by ocean currents, but this too ends up collecting in another place and causing localized pollution. For more on this, read the backgrounder from the Lenfest Ocean Program: Dilution cannot be assumed the solution for aquaculture pollution.
Clam beaches used by First Nations in the Broughton Archipelago (the area with the highest concentration of salmon farms in BC) have been destroyed by the accumulation of black muck and sludge that has been attributed to salmon farm waste.
The contaminants from salmon farms have also been linked to elevated levels of mercury in rockfish and parasites, tumors and lesions on ground fish harvested near salmon farms, impacting a traditional food source still used by coastal communities.
The chemicals and antibiotics used in farmed salmon production—from the toxic copper coating used as antifoulant on nets to the pesticide/paraciticide used to treat sea lice—all have impacts on the marine environment.
Closed containment systems offer a promising solution to the problems posed by open net-cages.