The Biology Topics of ecology involve studying the relationships between living organisms and their environment.
Fish Production – An Overview
Fish is an important aquatic food which is rich in proteins. A large section of the Indian population uses fish as food, particularly those living in coastal areas. It is highly nutritious and easily digestible. Fish can be useful in eradicating the problem of malnutrition. Fish liver oil is rich in vitamins A and D. Out of the total fish obtained from the Indian oceans, 45% is procured by India.
Fisheries are establishments connected with the capture, preservation, exploitation, and utilization of various types of fish, prawns, lobsters, crabs, oysters, other mollusks, etc.
On the basis of product, fisheries are of two types:
- Fin fishery: It is the capture, management, and exploitation of cartilaginous and bony fishes.
- Shell fishery: It is the capture management and exploitation of crustaceans (crabs, prawns, lobsters) and mollusks (oysters, mussels, octopods, etc.).
Depending upon the mode of obtaining fish, fisheries are of two types, capture, and culture.
1. Capture fishery:
The fish is caught in natural waters, both marine and inland. Modern technology is used for capture and storage before marketing. Electronic equipment is used to locate fish in the sea. Mechanized fishing boats and deep sea trawlers are often employed in capture fishery.
2. Culture fishery:
It is cultivating, rearing, and harvesting of fish. Culture fishery is also called fish farming or pisciculture. The growing of various types of aquatic organisms in water bodies is called aquaculture.
Differences between capture fishery and culture fishery
|Capture fishery||Culture fishery|
|1. It is a method of obtaining fish from natural resources.||1. It is a method of obtaining fish from fish farming (water agriculture).|
|2. There is no seeding and raising of fish.||2. The fish is seeded and reared.|
|3. Capture fishery is undertaken in both inland and marine waters.||3. Culture fishery is undertaken mostly inland and near the sea shore.|
In common usage, the term fish has often been used to describe a mixed assortment of water-dwelling animals, we speak of jellyfish, cuttlefish, starfish, and shellfish, knowing fully well that when we use the word “fish” in such combinations, we are not referring to a true fish.
A true fish is a gill-breathing, ectothermic, aquatic vertebrate that possesses fins and skin that is usually covered with scales. The word fish is commonly used both as singular and plural, but a zoologist uses fish to mean more than one kind of fish.
Seventy percent of the Earth is covered with water. Based on the water sources of fish production, the following three types of fisheries can be recognized.
- Marine fisheries: They include capture fisheries of oceans and seas.
- Freshwater fisheries: They include capture and culture fisheries in freshwater systems such as rivers, canals, lakes, reservoirs, tanks, ponds, and paddy fields.
- Brackish water fisheries: They include fishing activities in brackish water (slightly salty) such as estuaries (the last part of the river that gets tidal water from the sea), lagoons (shallow saltwater lakes separated from sea banks, coral reefs, etc.) and mangrove swamps (tropical trees growing in the mud of sea-shore).
Freshwater fisheries and brackish water fisheries are collectively called inland fisheries. With the increase in our population, fish production has increased both for food and as a business activity. Modern technologies are being used both for capturing and culture of fish in marine and freshwater ecosystems. In this section, we will study various methods for increasing the production of fish in all sorts of aquatic ecosystems.
Few Facts about Indian Fisheries (including both capture and culture)
- Total fish production in India – 7th position in the world
- Marine fish production in India – 10th position in the world
- Aquaculture production in India – 2nd in South East Asian countries
- Fish industry contribution – Rs. 400 crores annually as foreign exchange
Kinds of Freshwater Fish Culture Systems:
- Carp culture (composite fish culture)
- Sewage-fed fish culture
- Air-breathing fish culture
- Fish culture in cages
- Paddy-cum-fish culture
- Integrated fish culture
- Fish culture in cold water
- Fish culture in bundhs
- Fish culture in seasonal ponds
- Freshwater pearl culture
Marine Fishery – An Overview
India has a vast scope of marine fishery. Our marine fishery resources include a 7500 kms coastline and extensive deep sea. Marine waters providing profitable fishing are the Arabian Sea, Bay of Bengal, many small bays, gulfs, lagoons, coral reefs, etc. Central Marine Fisheries Research Institute (CMFRI) at Ernakulam, Cochin, Kerala has been set up to explore and utilize the marine resources of the country.
The following 12 marine fishes of India are the most preferred sea fishes or table fishes, i.e., popularly consumed fishes:
- Bombay duck
- Ribbon fish
- Flat fish or sole
- Flying fish
These marine table fishes are caught by fishing nets and gears operated by fishing vessels. A vessel that drags a net behind it is called a fishing trawler; such fishing trawlers fitted with electronic fish locating devices have been put into service for boosting deep-sea fishing. The modern technologies for catching more fish include echo sounders and the use of satellites to fish shoals or schools (assemblages of fish).
What is Aquaculture, and Why Do We Need It?
Aquaculture pertains to the production of useful (i.e., of high economic value) aquatic plants and animals such as fishes, prawns, crayfish, lobsters, crabs, shrimps, mussels, oysters, and seaweeds by proper utilization of available waters in the country. It is an important means of increasing the country’s food output. India has great potential for aquaculture because of its long coastline and numerous inland water spreads.
Aquaculture includes mariculture and freshwater culture fisheries.
Mariculture: The marine fishes cultured in coastal waters of India on a commercial basis include mullets, bhetki, pearl spots, sardines, eel, and milkfish.
Freshwater culture fishery of exotic carp has good prospects in lakes. These carps include the common carp, English carp, tench, and trouts. Trout hatcheries have been established in Kashmir and other places.
It includes (i) riverine fishery; (ii) reservoir fishery; (iii) lake or lacustrine fishery; (iv) pond fishery and (v) estuarine fishery. Inland capture fisheries are rapidly expanding in our country. The introduction of exotic species from abroad and inter-regional transplantation of fish from northern to southern waters have proved to be a great boon. Increasing pollution of water is adversely affecting inland fisheries. The construction of dams has harmed many regional fisheries. Indiscriminate fishing is also causing immense damage to fisheries.
The major share of fish production from inland resources is, however, through aquaculture practices. For table fish production, the common and most advantageous culture system is composite fish culture. Fish culture in an integrated fish culture system is also taken up with agriculture farming including paddy-cum-fish culture.
Some interesting fish culture systems are the following:
- Cage culture: Fish is cultured in large cages, made of bamboo or steel, which are lowered into the river. Generally, carnivorous species are cultured in cages.
- Integrated fish culture: Fish culture is practiced along with some agricultural crops such as paddy, banana, and coconut to give higher yields.
- Fish is also cultured in ponds near the poultry or piggery, and the excreta of these animals is used as food in ponds.
The fish species that can be stocked in paddy fields include Catla catla, Labeo rohita, Cirrhinus mrigala, and Clarias spp. (catfish), Channa spp. (Murrells), Mugil spp., fates calcarifer, etc. These species are able to live in the shallow water of paddy fields and able to tolerate high temperatures or turbidity.
Composite Fish Culture (Polyculture of Fish)
Fish production by culturing a single species in a pond (called monoculture) using old traditional methods gives a low yield; but if several species of fish are stocked together in a pond, the production increases with the same cost. Hence it is necessary to select species having different feeding habits so that all the available food in the pond is effectively utilized. Fast-growing compatible species are selected, so that, there is little competition between them, and all ecological zones are exploited for achieving maximum yield. This method is called composite fish farming or polyculture of fish.
Experiments have shown that Indian major carps (i.e., Catla, rohu, and mrigal) when stocked along with three species of exotic carps (i.e., silver carp, grass carp, and common carp; all three species are transplanted from China), the yield goes up 8-9 times, as compared to monoculture. The food habits of these six species are as follows:
- The silver carp (Hypophthalmichthys molitrix) is a surface feeder and feeds on phytoplankton.
- The catla (Catla catla) is also a surface feeder and it feeds on zooplankton.
- The rohu (Labeo rohita) feeds in the middle zone of the pond, i.e., column feeder, and feeds on decaying plants and detritus.
- The grass carp (Ctenopharyngodon idella) feeds on all macro-vegetation and consumes the aquatic plants/weeds not used by other species in this group.
- The mrigal (Cirrhinus mrigala) is a bottom feeder using decaying plants and detritus.
- The common carp (Cyprinus carpio) is an omnivorous bottom feeder.
These six species have complementary feeding habits and do not harm each other, and constitute a good combination of polyculture.
Important factors to be taken into consideration for fish culture include:
- Topography or location of the pond
- Water resources and quality
- Soil quality, i.e., the composition of particle size as well as nutrients.
The time of stocking also depends on the water temperature. Low water temperature (18-20°C) is most favourable for growth.
Qualitative and Quantitative Improvement of Fish and fish seed. The different fish used in the composite culture do not breed in the pond environment. The carps breed in rivers during monsoon months (July, August). The eggs and seeds collected from riverine water were seldom pure.
Fish seed is a commercial term for
- Spawn (fertilized developing eggs)
- Hatchlings (upto 4-5 mm in size)
- Fingerlings (adult-like fish)
The problem of quality seed and breeding the carp in ponds was solved by Alikunhi (1957) through the technique of induced breeding by injecting fish pituitary hormones (called hypophysation). This technique of induced spawning (release of fertilized developing eggs) in fishes led to the blue revolution through fish culture. Currently, synthetic hormones such as ovaprim, ovatide, and nova are used for induced breeding. This technique ensures the supply of pure seeds of fish in the desired quantity.