Fish farming
Fish farming or pisciculture involves commercial breeding of fish, most often for food, in fish tanks or artificial enclosures such as fish ponds. It is a particular type of aquaculture, which is the controlled cultivation and harvesting of aquatic animals such as fish, crustaceans, molluscs and so on, in natural or pseudo-natural environments. A facility that releases juvenile fish into the wild for recreational fishing or to supplement a species' natural numbers is generally referred to as a fish hatchery. Worldwide, the most important fish species produced in fish farming are carp, catfish, salmon and tilapia.[1]
Global demand is increasing for dietary fish protein, which has resulted in widespread overfishing in wild fisheries, resulting in significant decrease in fish stocks and even complete depletion in some regions. Fish farming allows establishment of artificial fish colonies that are provided with sufficient feeding, protection from natural predators and competitive threats, access to veterinarian service, and easier harvesting when needed, while being separate from and thus do not usually impact the sustainable yields of wild fish populations. While fish farming is practised worldwide, China alone provides 62% of the world's farmed fish production.[2] As of 2016, more than 50% of seafood was produced by aquaculture.[3] In the last three decades, aquaculture has been the main driver of the increase in fisheries and aquaculture production, with an average growth of 5.3 percent per year in the period 2000–2018, reaching a record 82.1 million tonnes in 2018.[4]
Farming carnivorous fish such as salmon, however, does not always reduce pressure on wild fisheries, such farmed fish are usually fed fishmeal and fish oil extracted from wild forage fish. The 2008 global returns for fish farming recorded by the FAO totaled 33.8 million tonnes worth about US$60 billion.[6]
Although fish farming for food is the most widespread, another major fish farming industry provides living fish for the aquarium trade. The vast majority of freshwater fish in the aquarium trade originate from farms in Eastern and Southern Asia, eastern Europe, Florida and South America that use either indoor tank systems or outdoor pond systems, while farming of fish for the marine aquarium trade happens at a much smaller scale.[7][8]
Indoor fish farming[edit]
Other treatments such as ultraviolet sterilization, ozonation, and oxygen injection are also used to maintain optimal water quality. Through this system, many of the environmental drawbacks of aquaculture are minimized including escaped fish, water usage, and the introduction of pollutants. The practices also increased feed-use efficiency growth by providing optimum water quality.[84]
One of the drawbacks to recirculating aquaculture systems is the need for periodic water exchanges. However, the rate of water exchange can be reduced through aquaponics, such as the incorporation of hydroponically grown plants[85] and denitrification.[86] Both methods reduce the amount of nitrate in the water, and can potentially eliminate the need for water exchanges, closing the aquaculture system from the environment. The amount of interaction between the aquaculture system and the environment can be measured through the cumulative feed burden (CFB kg/M3), which measures the amount of feed that goes into the RAS relative to the amount of water and waste discharged. The environmental impact of larger indoor fish farming system will be linked to the local infrastructure, and water supply. Areas which are more drought-prone, indoor fish farms might flow out wastewater for watering agricultural farms, reducing the water affliction.[87]
From 2011, a team from the University of Waterloo led by Tahbit Chowdhury and Gordon Graff examined vertical RAS aquaculture designs aimed at producing protein-rich fish species.[88][89] However, because of its high capital and operating costs, RAS has generally been restricted to practices such as broodstock maturation, larval rearing, fingerling production, research animal production, specific pathogen-free animal production, and caviar and ornamental fish production. As such, research and design work by Chowdhury and Graff remains difficult to implement. Although the use of RAS for other species is considered by many aquaculturalists to be currently impractical, some limited successful implementation of RAS has occurred with high-value product such as barramundi, sturgeon, and live tilapia in the US,[90][91][92][93][94] eels and catfish in the Netherlands, trout in Denmark[95] and salmon is planned in Scotland[96] and Canada.[97]
Fish farming in the fjords of southern Chile
Transport boats moored at fish processing plant, Mỹ Tho
Fish farm Högtind in Norway with feeding barge
