NEET Biology Strategies for Enhancement in Food Production / खाद्य उत्पादन में वृद्धि के लिए रणनीतियाँ Fisheries

Fisheries

Fishes are a valuable and easily accessible source of food, rich in protein, highly nutritious and easily digestible. By the aquatic animals, they are abundantly available from sea, rivers, lakes, ponds and marshes.

Aquaculture is the production of useful aquatic plants and animals such as fishes, prawns, shrimps, lobsters, crabs, molluscs by the proper utilization of small and large bodies of water. Pisciculture is the production and breeding of fishes by man in ponds.

India has abundant marine and inland fish resources. It has a cost line extending to 4667 Km long and a continental shelf of 2,59,00 square Km offering good scope for fish production. The fish production has increased many folds since India got independence. During 1990-91 the annual fish production of our country has been 38.22 lakh tons. The per capita consumption of fish in India is estimated at 1.51 Kg/year. India is at present the 6^th foremost seafood producing nations in the world.

(i) History: From pre-historic period, fishes have used as protein rich diet for human beings. The popularity of fishes has been mentioned in our religious books like Ramayana and Mahabharata also.

In west Bengal, Bihar and Orissa, the fish industry is about 1,500 years old. In Bengal every family traditionally has at least one pond for fishes.

 Classification of cultivable fish species:

(ii) Culture method: The success in fish culture and the high production of table - size fish through carp culture depends largely on the designing and construction of ponds. The basic principles involved in designing and construction of carp culture ponds are of very specialized nature and vary form region to region depending upon several factors like topography, soil types, water supply etc. The requirements with regard to the designing and construction of fish farm are entirely different from those attributed to agriculture and animal husbandry farms.

(iii) Types of Ponds: Ponds for carp culture may be broadly classified into three types: (a) the nursery ponds, (b) the rearing ponds and (c) the stocking ponds. The ponds which are small and shallow are used for raising fry from spawn (4-5 mm to 25-30 mm) may be termed as Nursery ponds or Nurseries. Ponds used for rearing fry up to fingerling stage (50 mm and above) are known as Rearing ponds. The rearing ponds are slightly larger but not proportionately deep and are used for rearing fry up to fingerling (50 mm & above) stage. While ponds which are used for stocking fry/fingerlings to obtain table-size fish may be called as stocking ponds. The stocking ponds are still larger and deeper (0.2 to 2.0 ha in size and 2 m to 2.5 m in depth).

(iv) Species Composition and Species Densities: Rearing of dietetically compatible species is one of the fundamental principles in fish culture. The divergent feeding habits of the Indian major carps and of the exotic Chinese carps are therefore taken advantage of in mixed culture. This divergence of feeding habits develop, as stated earlier, from advance fry stage and yet limited over- lapping in feeding habits is but to be expected. In view of this, trials were made with two, three. Four and six species compositions, within which variation in species densities or ratios were also attempted. Some of the combinations tried were as follows:

Silver carp + Grass carp                                                                 ::          1:1

            Catla + Rohu + mrigal                                                          ::         2:4:4

            Silver carp + grass carp+ common carp                          ::         4:3:3

            Catla + Rohu + Mrigal + common carp                              ::          3:4:1:2

            Catla + Rohu + mrigal + Grass carp                                     ::          8:3:1:4

            Silver Carp + grass carp + common Carp + Rohu             ::          2.4:1.2:2:2.4

            Catla + Rohu + Mrigal + Silver Carp + Common Carp      ::          2.4:4.8:1.0:2.4:2.4

(v) Types of Breeding

(a) Natural Breeding Habits: Major carps are essentially river fishes. They normally do not breed in confined waters Major carps breed in rivers throughout monsoon month's i.e. June to August. Major carps exhibit local migration in monsoon months. After travelling some distance against current in flowing waters, they enter shallow marginal inundated waters, where they breed. These fishes do not exhibit any parental care. Ova are small, numerous and fertilization is external. Females lay eggs and the males sprinkle its milt over the eggs which are fertilized by inter-mixing of water, Milt or seminal fluid milky white non-sticky and non-granular. Milt consists of innumerable microscopic structures called spermatozoa. These spermatozoa have small head. During the period of their existance, they are extremely active inhabiting a constant jerking motion.

There is sexual dimorphism in major carps. Females are generally larger than males Following factors are important which influence spawning of major carps.

(1) Right stage maturity of fish                         

(2) Heavy monsoon floods

(3) Extensive shallow spawning grounds    

(4) Current and flow of water

(5) Optimum temperature            

(6) High dissolved oxygen

(7) Increased pH                                    

(8) Turbidity

(9) Mineral solution and in suspension.      

(10) Instinct and physiological effect on fish.

(11) Endocrine secretion

Optimum temperature seem to be essential for breeding but major carp have known to breed over a wide range of temperature between . Some have suggested that excessive dissolved oxygen is essential but carps have bred in water where the dissolved oxygen was actually reduced due to mixture of pollutants after the floods. pH from 7.5 to 8.3 are recorded to be suitable for spawning. Turbidity do not seem to be essential for breeding of major carps. Fish spawning induced by lightning and thunder is also doubtful. Cloudy day, however, seemed favorable for breeding of carps. Endocrine and sex stimulating hormone of pituitary gland and series of subsequent physiological changes are important for spawning

(b) Bundh Breeding of Indian Major Carps: Indian major carps i.e. catla catla, Labeo rohita and Cirhinus mrigala do not naturally breed in confined waters though they attain sexual maturity in these environments. Their natural breeding takes place in rivers, certain reservoirs and in artificially constructed bundh type tanks where. Favourable conditions stimulate than for spawning Bundhs breeding contribute a lot to induce breeding of major carp fish.

The history of establishment of bundhs, as a source of major carp seed production is not clear. This type of bundh breeding appears to have originated from west bengal State , especially from the districts of Midnapore and Bankura with the expansion of fish culture industry in India, the bundhs have been established in several other States namely Madhya pradesh, Bihar, Uttar Pradesh, Andhra Pradesh, Rajasthan, Haryana and Punjab. The bundhs are of two types viz., Wet bundh and dry bundh.

(1) Dry Bundh: A dry bundh is a shallow depression enclosed by earthen walls, (locally known as bundh) on three sides and an extensive catchment area on the fourth. Bundhs get flooded during the south-west monsoon, but remain completely dry for a considerable period during the remaining part of the year.

The topography of the land has a great role to play in the location and distribution of the dry bundhs. In bankura district of west Bengal, most of the dry bundhs, are fed with water from storage tanks, constructed in the upland area.

(2) Wet Bundh: The wet bundh is a perennial pond located on the slope of a vast catchment area of undulating terrain, with proper embankments having an inlet facing towards the upland and an outlet towards the opposite lower ends. During summer, the deeper portion of the pond retains water containing breeders. The remaining portion is dry and is used for agriculture.

(c) Induced breeding: One of the dependable source of quality seed supply is by inducing major carps to breed in ponds by the use of pituitary hormone injections. Pituitary extract for inducing fish to breed is used extensively in many countries. Use of fish pituitary extracts for stimulating spawning of Indian Major carp is met with considerable success in recent years. The cost of seed production by induced breeding is very low as compared to the collection made from natural resources.

(vi) Hormone Injection: Major carps do not breed in ponds due to the fact that the environmental factors which are responsible for spawning in natural habitats are absent in confined waters. Sex stimulating hormones of the pituitary gland play an important role in the maturation of gonads and spawning in fishes.

The pituitary extract can be kept effectively and utilized successfully in inducing spewing of major carps through injection.

            The method of injection of pituitary extract are following types.

            (i) Intramuscular (ii) Intra paritonial           (iii) Intracranial

            (vii) Economic importance of fishes

• (a) Oils: Fish oils are employed in leather industry for chamoising.

Fish body oils are also employed in the manufacture of candles, lubricants, cutting oils etc. Liver oil is a valuable source of vitamin A and Liver oils are of medicinal use.

(b) Fish protein: It is used for edible and industrial purposes.

(c) Fish Meal: Waste products of fish are utilized for preparing feed for poultry, pigs and Cattle.

(d) Fish glue: It is a product mainly of tail regions of fishes such as cod, Haddock, pollack, Hake etc.

(e) Icing glasses (It is use for Comb, Purse, Riben and forming of wine.

(f) Shark fins.

(g) Fertilizers

(h) Controller of Diseases.

(i) Scavengers.