FISH FARMING (PISCICULTURE)
Fish farming, also known as Pisciculture, is the business of raising fish in large quantity, usually for food. Fish farming is the principal form of aquaculture.
SYSTEMS OF FISH FARMING
1. Cage system
Cage system of fish farming utilises existing water resources but encloses the fish in a cage or basket which allows water to pass freely between the fish and the pond. The method is also called “off-shore cultivation”.
Advantages of Cage System of Fish Farming
- Many types of waters can be used (rivers, lakes, filled quarries, etc.),
- Many types of fish can be raised
- Fish farming can co-exist with sport fishing and other water uses
Disadvantages of Cage System of Fish Farming
- Concerns of disease, poaching, poor water quality, etc., lead some to believe that in general, pond systems are easier to manage and simpler to start.
- Past occurrences of cage-failures leading to escapes, have raised concern regarding the culture of non-native fish species in dam or open-water cages.
- Even though the cage-industry has made numerous technological advances in cage construction in recent years, storms will always make the concern for escapes valid.
2. Irrigation ditch or pond system of fish farming
This involves using ponds or irrigation ditches to raise fish. Using this method, one can store one’s water allotment in ponds or ditches, usually lined with bentonite clay. In small systems the fish are often fed commercial fish food, and their waste products can help fertilise the fields. In larger ponds, the pond grows water plants and algae as fish food.
Control of water quality is crucial. Fertilizing, clarifying and pH control of the water can increase yields substantially, as long as eutrophication is prevented and oxygen levels stay high. Yields can be low if the fish grow ill from electrolyte stress.
3. Raceway Fish Farming
A raceway, also known as a flow-through system, is an artificial channel used in aquaculture to culture aquatic organisms. Raceway systems are among the earliest methods used for inland aquaculture. A raceway usually consists of rectangular basins or canals constructed of concrete and equipped with an inlet and outlet. A continuous water flow-through is maintained to provide the required level of water quality, which allows animals to be cultured at higher densities within the raceway
Freshwater species such as trout, catfish and tilapia are commonly cultured in raceways. Raceways are also used for some marine species which need a constant water flow, such as juvenile salmon, brackish water sea bass and sea bream and marine invertebrates such as abalone.
4. Tank System of Fish Farming
Tank system of fish farming is another artificial channel used in the business of fish farming. With a properly designed inlet system, the oxygen rich water will provide just the right current for good muscle tone while distributing new water evenly throughout the tank.
Copper alloys in aquaculture
Recently, copper alloys have become important netting materials in aquaculture. Copper alloys are antimicrobial, that is, they destroy bacteria, viruses, fungi, algae, and other microbes. In the marine environment, the antimicrobial/algaecidal properties of copper alloys prevent biofouling, which can briefly be described as the undesirable accumulation, adhesion, and growth of microorganisms, plants, algae, tube worms, barnacles, mollusks, and other organisms.