Water Pollution from Fish Farms

Abstract In 2014, global aquacultural production of fish for human consumption surpassed that of fisheries, amounting to c. 50 million tons annually. Freshwater aquaculture dominates, accounting for 87% of this total, with the remaining 6.3 million tons produced in marine systems. Water pollution from fish farms takes a variety of forms, from feed‐derived wastes to therapeutics, pesticides and other chemicals to pathogens/parasites and escaped fish. Recipient water bodies can also be significantly affected by the biomass for farmed fish, for example receiving water with low oxygen and high carbon dioxide levels. Depending on the type and intensity and type of production systems in use and in particular the kind of effluent treatment in place, the waste load per ton of fish production fluctuates strongly. In general, open systems such as floating net cages pose a larger local threat to the environment than land‐based closed systems, but the latter might have higher ecological cost on a global scale. Recirculating (RAS) and integrated (IMTA) aquaculture systems have been developed to minimize water consumption and effluent load, and the large‐scale implementation of such systems in the pond farms of China and other Asian countries, which dominate global aquaculture, reflects a significant effort to reduce negative local impacts on recipient water bodies. The potential for alternative added‐value usage of wastes generated in fish farms, for example as fertilizer or in biogas production is currently underexploited.