Wastewater is pumped through treatment systems that clean and re-filter circulated water before returning it to the fish tanks. These recirculating systems can be built on land, allowing farming to take place all across the country. Compared to other raceways, RAS aquaculture has less wastewater and overall water requirements. This type of farming also eliminates risks associated with environmental harm to ocean habitats. A wide variety of species grows well in these tanks such as arctic char, salmon, trout, bass, and sturgeon.
These pens are situated in coastal waters and allow fish to grow in an open ocean environment. Species such as salmon, trout, and tilapia are farmed using this method as it applies to both saltwater species as well as freshwater species. Nets pens are anchored to the bottom and allows for water to freely flow through them. Pens are typically constructed from welded steel pipes, heavy duty rubber hinges, and mesh/net screens.
These cages differ from open-net pens, as they are submersible cages in deeper water farther off the coast. With stronger oceans currents the farther out you go, water is filtered out and diluted more easily than with open-net pens. Offshore cages are attached to the sea floor and to buoys on the water’s surface. Species such as kanpachi, cobia, sablefish, and bass do well in off-shore cages. These cages are typically stronger than open-net pens, and continually becoming more secure as newer technology develops.
Sometimes referred to as “flow-through” systems, raceways can be inside or outside and are highly advantageous in allowing for easy fish monitoring and feeding. This system consists of long basins with continuous water flow to farm freshwater species like trout and tilapia. Incoming water is maintained at the appropriate temperature and salinity for the species being farmed. Raceways are most often constructed from concrete or pollster resin.
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Different from any other production method, this method combines finfish species, shellfish, and marine plants (seaweed and kelp) boosting the environmental and economic benefits of aquaculture. This farming method is similar to polyculture on terrestrial farms using co-cultivation of different species. The salmon effluent and food waste are able to be absorbed or extracted by mussels and the kelp is able to dissolve other waste products such as nitrogen and phosphorus.