Further Pollution
Effluent from salmon farms is not captured. Instead it flows directly, untreated, into the marine environment and into contact with wild species.
Waste from fish farms is a
mixture of fish feces, uneaten food pellets, heavy metals (e.g. copper, zinc),
drugs and drug residue, streaming continuously into the waters off B.C.'s
coast.
In the open net-cage systems
now used, the waste spills through the cages, into the surrounding water and
onto the ocean floor below the cages. Some of the benthic waste is eaten by
crabs and other shellfish thereby potentially having impacts on the entire
food-chain (see Introduction of "Therapeautants" into the Marine Environment).
The bulk of the waste is left on the ocean bottom under the farm. There it
decomposes, using up the oxygen in the surrounding water (eutrophication). Even
if the farm is moved, the waste left behind renders the seabed uninhabitable
for other marine life for up to five years after the farm has relocated.[1],[2]
The contaminants from open net-cage salmon farms have also been linked to elevated levels of mercury in rockfish, further affecting a traditional food source still used by coastal communities.[3]
