Aquaculture can refer to many different methods for raising aquatic species.
Several methods are used in fish farming, with the use of culture tanks as the most common. Large, plastic tanks can be used to raise fish from small fry to adult maturity. Competent water recirculation systems are required to ensure optimum water quality, in terms of temperature and contamination. Depending on the species and system, the fish can either be fed high protein fish meal products or allowed to consume algae grown in the tanks. Manmade or natural ponds are common in fish farming as well. Lastly, some aquatic species are grown in raceways that employ extensive water treatment and recirculation systems
Where fish farming refers to freshwater operations, mariculture occurs in saltwater conditions.
The major United States mariculture industry is for Atlantic salmon, with minor amounts of mollusks and shrimp. But Asia has extremely significant amounts of mollusk and shrimp mariculture production, with China and Japan the major players.
There are many methods to mariculture. One of the oldest, but probably least efficient is to raise fry or fingerlings n a hatchery and then release them into their wild settings. Mollusks can be grown on ropes suspended beneath rafts in coastal areas. Ponds are the most common form of mariculture for fish and shrimp. After raising the fish and shrimp to the fingerling developmental stage, they are transferred to a pond that has been filled with saltwater from nearby natural sources.
Other fish, particularly salmon, are raised in floating cages in saltwater estuaries and coastal areas off the coast of Nova Scotia, Newfoundland and the northeastern United States.
Each aquaculture method offers has its pros and cons. Issues with farmed fish center on controlling disease or damage to the fish themselves. Regardless of the species, farmed fish live in much higher concentrations than what they would naturally. Their close quarters allow for diseases or sea lice to spread easier than in the wild conditions. In addition, their higher concentrations bring more actual physical contact between fish, which can result in bruising and damage to their outer surfaces. While mariculture fish may be in less physical concentrations than farmed fish, they still are in higher numbers per acre than their wild cousins. This can result in higher concentrations of their waste products, which can have an impact on the habitat for wild fish if the mariculture occurs in pens in coastal saltwater areas. Another side effect of mariculture is the higher risk of fish escaping their pens or ponds to live naturally, either causing competition or genetic dilution complications for the wild populations.