Salmon Aquaculture

Impacts & Issues: Waste

Fish farm with anti-fouling-treated nets, photo by Barbara WatsonEvery day BC's fish farms produce huge quantities of untreated waste that goes straight into the ocean.

Fish farm waste consists of fish feces, uneaten food pellets, drugs and drug residues, pesticides, fungicides, and feed additives. Fish farm nets are often painted with a highly toxic copper solution in order to prevent naturally occurring marine organisms like barnacles and muscles from growing on the nets. Many of the chemicals used in aquaculture have been adopted from other industries; the impact on marine ecosystems is unknown.

A typical BC salmon farms holds between 500,000 and 1,000,000 farmed salmon, which translates to a significant amount of waste.

Photo by Robert Mountain 

Left: clam harvested next to fish farm
Right: clam taken 20 km away from fish farms

Untreated fish farm waste spills through the cages into the open ocean and onto the ocean floor. It collects at the bottom of the ocean, smothering the sea floor under the farms. As this layer breaks down, it consumes the oxygen vital to shellfish and other bottom-dwelling sea creatures. When this happens, the farm is sometimes moved to a new location. The waste left behind can leave the seabed unlivable for other marine life for up to five years after the farm has relocated.

Many salmon farms have been relocated to areas with tidal currents that flush the farm waste "away". This waste can then accumulate in other locations and cause localized pollution away from beneath the farm. Clam beaches near salmon farms are sometimes found covered with sludge and contaminated with decomposing fish feces and waste food from the farms, leaving the once pink and healthy clams black and inedible. 

Closed containment technology offers a valuable solution to the waste issue and oher impacts from open net-cage salmon farming.

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