Around 475 B.C., Chinese historian Fan Lai described fish farming techniques in his book, "The Classic of Fish Culture." Over the centuries, fish farming has continued to be used around the world to raise fish and other aquatic life. Farm raised fish are mainly used for human consumption, but fish farms also produce ornamental fish, roe, fish oil, bait fish and fish for pet food. Fish farming techniques have evolved to meet the growing global demand for fish and to incorporate technological advancements in fish farming equipment.
Types of Fish Farming
Fish farming can be broken down into two basic categories. With extensive fish farming, fish are held in nets or cages in their native habitat, such as lakes, rivers or oceans. Intensive fish farming refers to the containment of fish in ponds or tanks, where nearly all of their nutrition is provided by the fish farmer.
Feeding the Fish
Fish farming techniques for feeding fish depend on the species of fish being raised. Some fish require vegetation, some require zooplankton and others will only eat smaller fish. In a polyculture operation, where multiple species of aquatic life are raised in the same body of water, a balance must be found that will prevent one species, or one type of food, from overtaking the growing environment.
Monitoring Water Quality
With intensive fish farming, the body of water is a closed ecosystem. If a virus or chemical imbalance occurs, it can spread quickly to the entire system. Fish farming techniques must be used to keep runoff from effecting the water, to insure that harmful chemicals cannot enter the system and that diseases are prevented or held in check. Electronic devices are available that perform constant checks for variations in water quality, oxygen levels and temperature. Some devices will notify the fish farmer if test results fall out of an acceptable range.
Monitoring Oxygen Levels
Different species of fish require different oxygen levels. Farmers use a variety of methods to replenish depleted oxygen in the water such as bubblers, paddle wheels, forced air and oxygen tablets. Weather events or biological conditions in a pond or tank can quickly alter oxygen levels. Fish farmers must react quickly or the entire season's crop can be lost in a matter of hours.
Closed Loop Systems
With a "closed loop" system, fish are generally raised in tanks and the water is circulated through the system using pumps. The functions of the individual components of a closed loop system may vary, depending on how much room, time and money the fish farmer wants to dedicate to the operation. Basically, a closed loop system will provide separate tanks for raising fish, cleaning debris from the water, replenishing oxygen and converting harmful chemicals from waste into beneficial biological organisms. A closed loop system is more expensive to set up and maintain, but fish density may be increased to provide a higher yield to the fish farmer.