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Maintenance and Management of Fish Farm, For the effective fish culture or fish rearing the maintenance and management of fish form is very, important aspects. Depending on the construction of pond Suitable species of fishes should be selected, and their culture is practised carefully., ➢ Required procedures for the maintenance of bond are given bellow:, (1) Dike preparation should be property checked. Repairing the broken parts of the dike, cleaning the, screens and overflow drainage system should be watched constantly., (2) There is need to check overcrowding in ponds., ➢ There are some principal measures for the maintenance of pond are described below:, 1. Restoration and Improvement of Pond Bottom:, It is essential for all the ponds drain or dry once in a every year., (i) Draining reduces mineralization of soil particularly when it has grown rich in cellulose contents, owing to accumulation of submerged vegetation., (ii) Pond draining destroy fish parasites, disease causing agents, harmful insects, leeches, etc., (iii) Remove the roots of emergent vegetation lying deep in the soil use up nutrients., (iv) After drying the ponds, the productivity is increases., (v) After drying of pond, it is possible to repairs the pond, which cannot possible when the pond is under, water can be carried out after drying the pond., 2. Liming:, After drying, lime is sprayed over the bottom of the pond which improves its productivity., (i) Liming has an antiparasitic action., (ii) It destroys unwanted algae and aquatic weeds for a short period of time., (iii) It kills harmful aquatic insects and their larvae., (iv) It improves the pH- of Pond soil and is restored to almost normal i.e. between 7.0 to 9.0., (v) Calcium of lime neutralises the harmful action of Mg, Na and K salts., (vi) Cellulose components deposited at the bottom by weeds are decomposed by lime., (vii) Liming brings about the mineralization of organic matters and so prevents spreading of parasites, and the bacterial diseases., (viii) In presence of lime the ammonium compounds are nitrified into nitrites and nitrates., (ix) By neutralising acid, normal alkalinity is restored., (x) Liming conditions the pond and acts like fertilizer as well., The types of limes, their respective doses and the methods of application are determined according to, the physico-chemical and biological properties of the ponds. Liming is done by spreading the lime, uniformly over the pond’s bottom. The spread layer is retained as such for about 2 weeks, during which, all the germs, cysts, etc. are killed. The other exposed sides of ponds are also covered with the lime., The liming rate for different types of lime in the pond soil:, Ground lime stone (CaCO3)-1140 kg per hectare, Hydrated lime [Ca(OH)2]-114 kg per hectare- is cheapest and more concentrated, Quick lime (CaO)-200 kg per hectare, Calcium cynamide (CaCN2)- It is toxic and the toxicity is retained for 20-30 days, Since the rate of application of lime is determined by the pH of soil, the quantity of quicklime, required with respect to pH should be as below:
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3. Pond Fertilization:, Fertilization is necessary in nursery and rearing ponds, for developing natural food and saving artificial, food. Phytoplanktons, the primary producers of pond converting the inorganic components into organic, form required for their propagation and growth. Therefore, the significance of pond fertilization is to, cultivation and propagation of various fish food organisms for the cultured fish. In other words, higher, the utilisation rate of energy, greater is the fish production., Pond Fertilizers:, There are two categories of fertilizers used in fish culture ponds i.e. Organic and Inorganic, (i) Organic fertilizers:, Organic fertilizers are of animal and plant origin. They are added to the pond and the microbes, decompose them to release their K, N, P and C contents, which are then utilised by the phytoplanktons, constituting the food of fishes. Compost fertilizer is applied at the rate of 2000 kg per hectare for three, times with an interval of three months. It is kept at the corners of the pond so that it slowly releases, nutrients in pond water., The manures often used in fish ponds are:, (a) Faeces and urine of livestock and poultry., (b) Green manures., (c) Compost., (d) Silkworm faeces., Nature and Characteristics of Organic Fertilizers (Manure):, (a) Faeces and Urine of Livestock and Poultry:, Pig manure contains much organic matter and other nutritional elements such as N, P and K. Pig manure, is a fine complete manure. Pig faeces are with moisture content from 70-77%, containing more N than, other livestock faeces (C/N, 14 : 1)., (b) Cattle Manure:, The elements of cattle manure are similar to those of pig manure. Cattle manure contains less N than, pig manure (C/N, 25 : 1), cattle urine contains more N than pig urine in the form of hippuric acid., The average daily excreta of a cow of about 500 kg weight is 25 kg in which the ratio of faeces and, urine is about 3:2. Normally the cattle dung consists of about 75-85% moisture, 15-25% organic matter, and 2-5% mineral matter. The organic matter of dung chiefly comprises of 78-90% of total, carbohydrates, 9-18% of crude protein and 2-5% of other extract., (c) Poultry Manure:, It includes the faeces of chicken, ducks and goose. It is rich in both i.e. organic and inorganic matters., Liquid and solid excreta are excreted together hence, there is no urine loss. Poultry manure ferments, quickly and their N2 is mostly in the form of uric acid which cannot be absorbed directly by plants. If, the droppings come from the cages or dropping pits, superphosphate may be added at the rate of 1 kg/, day/100 birds. This improves the fertilising quality. Poultry manures are more effective after, decomposition. The organic fraction of the poultry excreta contains 21.5% crude protein, 1.9% ether, extract, 13.4% crude fibre and 42.9% N2 free extract., (d) Goat and Sheep Manure:
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The droppings of goat and sheep make a very good quality of manure, which is applied in cultivated, lands as common practice by millions of farmers., The chemical composition of their excreta has a dry matter content of 42-48%. The organic fraction of, dung component comprises 52-93%. Sheep and goat manure contain about 3% N, 1% P2O5 and 2%, K2O., (f) Silkworm Dregs:, Silkworm dregs are composed of silkworm faeces, moult residues and mulberry residues. These are rich, in organic matter (87%) and nitrogen (13%). They make good fish food and also used as manure., (g) Green Manure:, All wild grasses, cultivated plants of the composite family with some gramineous and leguminous plants,, which are nutritively rich, less fiberous and are easily putrescible, if used as manure, are termed green, manure. With the rapid development of fish culture vegetable wastes and other non-toxic plants with, soft stems and leaves are also used to fertilize the water., (h) Compost:, Compost manures are the decayed of roots, twigs, leaves, stubble crop residue and allied refuge, which, are decomposed along with animal wastes. Mixing various manures together may easily produce a, fertilizer that is more suitable for fish pond., (ii) Inorganic Manure:, These include various inorganic chemicals such as superphosphates, slag etc. Inorganic manures are, also referred to as chemical fertilizers., They are of four main types:, (a) Phosphorus fertilizers, (b) Potash fertilizers, (c) Nitrogenous fertilizers, (d) Micronutrients., , (a) Phosphorus Fertilizers:, Phosphorus fertilizers are considered indispensable because, the soil is usually poor in the, phosphorus contents. Single super phosphate (SSP), or triple super phosphate (TSP), and slags are used, as additive phosphorus fertilizer in pond culture system. They are most effective for the growth and, multiplication of algae and the algal blooms., The application rates for phosphorus fertilizers is 25-30 kg/hector for basic slag and for SSP-114, kg/hector and for TSP-57 kg/hector. The amount may be decrease or increased on the basis of fertility, of pond soils., (b) Potash Fertilizers:, Potash (a potassium fertilizer) favours the growth of submerged plants and so increases the amount of, natural food in water. Often the potassium fertilizers are mixed with phosphate fertilizers and supplied, to the ponds, particularly when the soil is poor in potassium content and has low alkalinity., (c) Nitrogenous Fertilizers:
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The soils normally have a good amount of nitrogen which varies from 25 mg per 100 gm in less fertile, soil to about 70 mg per gm in highly fertile soil. A pond poor in phosphorus contents, cannot use nitrogen, properly. It is, therefore, advised to apply phosphorus and nitrogen together in a ratio of 1:4. Nitrogen, content in liquid ammonia is 12-16%, in ammonium sulphate 20-21% and in urea 44-46%., Aqueous ammonia is readily volatilised, hence should not be exposed to the air for a long time. It is also, applied in killing the unwanted predators during prestocking management operation. Liquid ammonia, can be used sufficiently 7-8 days before stocking fish seeds and can be used till the culture is going on., In contrast, ammonium sulphate can be used as additive fertilizer during culture period. However, urea, (NH2CONH2) i.e., carbamide does not ionize when dissolved in water. Hence, cannot be absorbed, directly by plants. Only after decomposition they are ionized and made available to plants and, phytoplanktons. Inorganic fertilizer i.e. chemical fertilizers are not required in nursery ponds if manured, with organic fertilizers e.g., mahua oil cake (2000 kg per hectare)., (d) Micronutrients:, Micronutrients are required in traces but have been found beneficial for the growth of cultivable fishes., These are mixed with other fertilizers and supplied to pond., 4. Control of Various Physico- Chemical Factors:, All the physico-chemical parameters of water should be thoroughly checked and corrected, during total period of cultivation. This is necessary because their concentrations may alter depending, upon the environmental conditions. The pH of fish pond water may change in rainy season that causing, acidity, O2 concentration and should be corrected quickly by aeration or by other means., 5. Control of Predatory and Weed Fishes:, The fishes which feed upon cultivable species of carp hatchlings are called predatory fishes., Weed fishes are those which consume the aquatic vegetation and thus, compete with the fishes under, cultivation. Certain predatory fishes breed prior to the breeding of major carps in pond waters and go on, feeding the available planktons with fast increase in their growth and size. The Predatory and Weed, Fishes should be removed from the pond. It is desirable to completely eradicate the predatory and nonpredatory minnows and weed fishes from culturable pond through management., 6. Control of Aquatic Insects:, For maintenance of fish farm, the eradication of aquatic insects is an essential requirement., Eradication of harmful aquatic insects play an important role in increasing fry survival rate., The piercing, cutting and sucking type of mouth parts of harmful aquatic insects cause direct or indirect, death of culturable tiny fishes. However, common insects found in the culturable ponds being smaller, in sizes, cannot make any harm to rather bigger sized fishes including fingerlings and yearlings. Thus,, eradication of insects in the stocking tank is not compulsory., Out of eleven orders of class insecta, three orders namely Hemiptera, Coleoptera and Odonata are, relatively more common in freshwater ponds. Waterbugs of order Hemiptera are relatively more, dangerous. Belostoma, Lithocerus (Giant water bug), Nepa, (water scorpion), Ranatra (water stick, insect), Notonecta (Back swimmers), Geris (water spider) etc., are other harmful insects belonging to, order Hemiptera. Order Coleoptera includes Cybister (water beetles), Dytiscus (diving beetles), Gyrinus, (whirling beetles), Hydrophilus (scavenger beetles), etc. Both larval and adult life complete throughout, in pond water. The death of the fry is due to their strong cutting mandibles. Dragon fly and dumsel fly, are common aquatic insects belonging to order Odonata. The larval forms are aquatic while adult forms, are terrestrial. Their nymphs are provided with sucking type of mouth parts and cause death of culturable, fish fry., 7. Eradication (Control) of Predatory Aquatic Insects:, Effective control of aquatic insects is obtained by using insecticides. Gamaxene when applied, @ 0.6-1 mg/l, can safely eradicate aquatic insects within 1 to 11 hours. Pure gamaisomer of benzene, hexachloride soluble in ethanol can kill aquatic insects within 6 hours at 0.01 mg/l concentration. The, insecticides, however, also affect adversely zooplankton and fish spawn. Therefore, the insecticide
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should be of such type which may affect only insects but not the zooplanktons. Spraying oil to kill the, insects, which come up to the surface water to respire, is well known principle and a routine practice in, malaria control. Emulsion of mustard or coconut oil and cheap washing soap in the ratio of 56:18, kg/hect. has been reported from CIFRI Cuttack to kill pond insects. Kerosene oil is also practiced among, pisciculturists for effective eradication of aquatic insects. To kill water centipedes, quick lime can be, applied before fry stocking. A drug namely dipterex crystal (concentration 90%) can be scattered into, the entire pond in order to kill aquatic centipedes in nursery ponds., 8. Artificial Feeding:, The stocking of nursery pond is best done at the rate of 12 -20 lakhs/hector in late evening. Soon, after stocking, spawns start feeding voraciously on zooplanktons. Till two days of stocking no artificial, food is given to spawns. After this period artificial feed along with natural fond enhances the growth of, spawns. An artificial feed comprising of a mixture of dried, finally powdered and sieved aquatic insects, (back swimmers), small prawns and shrimps and cheap pulses in the ratio of 5:3:3 gives better result in, enhancing the growth of spawns. The use of powdered algae and other aquatic weeds as fish feed has, also been suggested. The artificial feed may be sprayed at a fixed place during specified hours or fed as, a thick paste in small shallow earthen vessel, kept suspended in the pond water. Feeding is done usually, in morning hours., 9. Harvesting:, By draining the pond or by netting, harvesting i.e., fishing is done. By draining, harvesting is, complete and predators can be eliminated. Much less labour is required and the pond can be dried,, cleaned, repaired and soil enriched by applying fertilizers. If the ponds are constructed in row, loss of, water can be avoided and ponds are drained by turns.
