Fish waste and excess feed from growing carnivorous fish, like salmon, can cause rapid algae growth that pollutes the water surrounding aquaculture pens. In severe cases, this creates a dead zone where the oxygen normally dissolved in the water is exhausted, killing fish and other animals and leaving a murky, foul-smelling mess.
While there are many other contributors to nutrient pollution worldwide, on a local scale aquaculture can be the primary nutrient polluter.
According to 2009 data from the Yendegaya Foundation, a salmon farm with approximately 3.5 million fish releases the same amount of waste as the sewage from a city of about 169,000 people. This waste collects under net pen operations, altering the seafloor and surrounding waters.
A wide range of chemicals are typically used in aquaculture, including antibiotics, parasiticides, pesticides, growth hormones, anesthetics and dyes. These chemicals are used regularly in aquaculture despite the potential for harm to human health and ocean ecosystems.
In net pen aquaculture operations, the containment of chemicals is non-existent, allowing chemical pollution to disperse into the marine environment where it may impact or accumulate in other species.
Furthermore, the pesticides used in aquaculture operations lack specificity, potentially impacting a wide range of organisms when released into the marine environment.