Preparation and Management of Nursery, Rearing and.pptx

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1. Preparation and Management of Nursery, Rearing and grow-out ponds

2. Ponds where spawn are reared to fry stage . In carps it takes about 15-20 days to grow spawn to fry size Nursery ponds

3. These are ponds where fry are grown to fingerling size. In carps it takes about 2-3 months to rear fry to fingerlings size. Rearing ponds

4. In these ponds fingerlings are stocked and grown to harvestable size . Carps grow from fingerlings to marketable size in about 10-12 months. Grow-out ponds

5. The ponds need to be prepared such that the pond environment provides optimum condition for growth of the fish. The pond environment should be free from predators, aquatic weeds, weed fish; it should have optimum water quality parameters and sufficient natural food should be available in semi- intensive culture systems. Pre stocking Management

6. The steps involved in pre-stocking and post-stocking management are similar in the nursery, rearing and grow-out ponds. An additional step in the pre-stocking management in nursery ponds is the eradication of aquatic insects which predate on spawn and fry Contd.

7. The pre-stocking pond management of drainable ponds, which can be dried, is as follows. Draining and drying Ploughing Liming Filling with water and Fertilization Contd.

8. Perennial un-drainable water bodies require the following additional pre-stocking management measures. Control of aquatic weeds Eradication of weed fish and predatory fish and animals . Contd.

9. Pond needs to be drained a dried before culture operations begin Drying facilitates in Oxidation of organic matter Degassing of toxic gases such as ammonia and hydrogen sulphide 1.Draining and drying

10. It kills pathogenic micro organisms It kills predatory and weed fish It kills unwanted aquatic plants Ponds should be dried for 7-10 days till the soil cracks the ponds with clayey soil ; in sandy soils they should be dried till the soil supports a person and foot prints do not form on the soil. Contd.

11. The ponds should be ploughed using wooden ploughs or power tillers or tractors Ploughing helps in mixing up of soil which helps in oxidation of organic matter Proper degassing of soil from toxic gases Mineralization of nutrients . 2.Ploughing

12. The productivity of fish ponds depends on soil qualities such as Texture Water retention pH Organic carbon Available nitrogen Available phosphorous 3.Liming

13. Pond bottom is important for productivity since process of mineralization of organic matter and release of nutrients to the overlying water takes place Liming helps in improving the quality of the pond soil, thus enhancing productivity . It also corrects soil pH ; the desirable pH is 6.5 – 7.00 Contd.

14. A range of liming materials are used such as Agricultural lime or calcite (CaCO 3 ) Dolomite [ Ca Mg (CO 3 )] Calcium hydroxide/slaked line Ca(OH) 2 Calcium oxide/quicklime - CaO Contd.

15. The dose of a particular variety of lime depends on its effectiveness and soil pH Generally 200-500 kg/ha of lime is used for application to pond soil After application, the lime should be mixed with the top soil with light ploughing . Quick lime is preferred for applying to soil Calcite agricultural lime for application to water after stocking of the ponds Contd.

16. Liming helps in Correcting soil pH Mineralization of organic matter Release of soil sound phosphorous to water Disinfection of the pond bottom Contd.

17. Fry and fingerlings of most fish such as carps feed on zooplankton Sustained zooplankton production in ponds depends on good phytoplankton and bacterial base This is maintained through adequate availability of nutrients such as Nitrogen, Phosphorous carbon and micronutrients in ponds. 5.Pond fertilization

18. Natural availability of these nutrients in ponds will be inadequate . Hence they need to be added through external sources for sustaining good plankton growth Nutrients are added to water through organic manures and inorganic fertilizers. Contd.

19. Organic manures are rich in carbon and contain nutrients such as N and P in small amounts. They decompose slowly and release the nutrients slowly They promote the growth of zooplankton through saprophytic food chain Organic manures

20. They promote sustained growth of phytoplankton and zooplankton for longer periods of time Several types of manures such as cow dung, poultry litter, pig dung, horse dung etc., can be used to fertilize fish ponds. Contd.

21. Pig manure Cattle manure Poultry manure Goat and sheep manure Night soil Silkworm dregs Green manure Vermicompost Biogas slurry Organic manure

22. Most common manures used in fish ponds are cow dung and poultry manure Raw cow dung is generally applied at a rate of 5-10 tons/ha 15 days before stocking. It can be also applied in phases; 2/3 of the amount as basal dose and a second dose after a week of stocking Contd.

23. Poultry manure is 2-3 times richer than cow dung in the content of nitrogen and phophorus . Hence half the dose of cow dung is used , when poultry manure is applied to the ponds. Contd.

24. Nutritional elements

25. Biofertilization has been observed to be a potential biotechnological tool improving the contribution of biologically fixed nitrogen to the total nitrogen budget of fish pond ecosystem Azolla is used as a biofertilizer Biofertilizer

26. It is an aquatic fern with wide distribution all over the world having the capacity of assimilating atmospheric nitrogen through cyanobacterium Anabaena azollae , a symbiotic blue green algae present in cavities on the dorsal lobe of the leaf

27. Azolla is a heterosporous fern belonging to the family azollaceae with 7 living and 20 extinct species

28. Composition of A zolla in dry weight present is as follows

29. For long run use of azolla as biofertilizer , it is necessary to go for azolla multiplication

30. These are concentrated forms of nutrients such as N and P Urea or ammonium sulphate is used as a source of N while single or triple super phosphate is used as a source of P Inorganic fertilizers promote the production of phytoplankton on which zooplankton production depends. Inorganic fertilizer

31. Their action is very fast and when used in excess quantities promote blooms of undesirable Blue Green Algae (BGA) Hence they should be used cautiously in fish ponds A combination of organic manure and inorganic fertilizers will promote the growth of phytoplankton quickly which will sustain for a longer period of time because of fertilizing with organic manures. Contd.

32. Large earthen ponds are usually infested with submerged ( Hydrilla , Najas , Ceratophylum and utricularia ) Emergent ( Trapa , Myriophyllum , Vallisneria ), floating ( Azolla , Pistia and Eichhornia ) and marginal weeds ( Typha and phragmites ). Control of Aquatic Weeds

33. Weeds cause several problems in fish ponds They compete for nutrients with phytoplankton thereby reducing the natural productivity for the ponds. Prevent light penetration and suppress the production of phytoplankton Contd.

34. Cause oxygen super saturation during day and oxygen deficiency during night Harbor aquatic insects and predatory fish Hinder free movement of fish and reduce their living space Cause problems during harvesting by hindering netting operations. Contd.

35. Increase siltation in the pond , reducing pond depth over a period of time Therefore growth of aquatic weeds needs to be controlled and their density reduced in fish ponds Contd.

36. Aquatic weeds can be controlled by employing methods such as Manual Mechanical Chemical and Biological Contd.

37. The method selected depends on factors such as Pond size Extent of weed infestation Time available Cost Contd.

38. Human labour is employed with or without the aid of simple implements Emergent and marginal weeds are removed by pulling them with hand or can be kept under check by cutting their floating leaves repeatedly Manual method

39. The floating weeds can be either hand picked or removed by coir, wire or nylon nets Rooted submerged weeds – handpulled bottom rakes, bamboo poles with toothed prongs Contd.

40. Underwater weed cutter Weed harvester Dragging Chaining Dredging Draining Drying Ploughing Raking It involves cutting of weeds followed by secondary operation of collection and disposal Mechanical method

41. Inorganic chemicals – Sodium arsenite Organic chemical – Xylene Auxin type regulators – 2, 4 dichlorophenoxy acetic acid (2,4 D) Algicides – rosin- amine – D acetate These can be sprayed over the foliage, water or in the soil where root penetrates Chemical control

42. Floating weeds @0.02 kg/ha Marginal weed and Emergent weed – Foliar spary of sodium salt 2-4 D @5 kg/ ha and @1.5 kg/ha Submerged weed – Sodium arsenite @5-6 ppm Algal bloom and filamentous algae – Copper sulphate @0.025 to 0.5 ppm Contd.

43. A number of herbivorous fish species are being tested as aquatic weed control agents Fishes that control aquatic weeds are classified as Grazer - Eats stem and foliage Mowers – eats lower part of aquatic plants Roilers and rooters – Stir the bottom sediments for foraging for food and preparing nests Algae feeder – Consumes filamentous algae Planktonic feeders – feeds on filtered microscopic algae Biological control

44. Ctenopharyngodon idella , Puntius gonionotus Osphronemus gorami Tilapia mossambica Common carp Golden carp Gold fish Milk fish Contd.

45. Weed as fertilizer Weed as feed for animal / bird and fish Weed as leaf protein Weed as food crops Weed as a source of energy Weed as wastewater treatment Aquatic weeds for pulp, paper and fiber Other use Control through utilization

46. Predatory fish severely affect survival of fish primarily in nursery and rearing ponds. Weed fish compete with stocked fish for food, space and oxygen and result in reduction in production of desirable fish. Common predatory fish are murrels (Snakeheads), Catfishes such as Wallago attu , Clarias batrachus , Heteropneustis fossilis , Ompak sp . etc.,  Eradication of Predatory and Weed fish

47. Weed fish include Puntius , Barbas Danio , Aplocheilus , Anabas etc., Most predatory and weed fish breed prior to the onset of carp breeding They infest the ponds before carp fry and fingerlings are stocked Contd.

48. Hence their eradication prior to stocking of carps is necessary Dewatering followed by sun drying is most effective way to control weed and predatory fish. In ponds which cannot be dewatered, piscicides are used. Contd.

49. A suitable piscicides should have the following characteristics Effective at low dose Not injurious to people and animals Doesn’t make fish unsuitable for human consumption Gets detoxified quickly Easily available and economical Contd.

50. Following are the three types of piscicides that can be used to eradicate weed fish and predatory fish Plant origin Chemicals Pesticides (Chlorinate hydro carbons and organophosphates) Piscicides of plant origin Types of piscicides

51. Rotenone is the active ingredient It is a contact poison Lethal to other organisms also such as zooplankton, Benthos and insects 1.Derris root powder

52. Dosage is 4-20 ppm (mg/l) The powder is mixed thoroughly with water and sprayed all over the pond It is effective only on sunny days when the temperature is above 25 degree Celsius It is less effective in cold waters Contd.

53. The active ingredient is saponin It causes lysis of the RBC and kills fish, frogs, snakes and turtles Dosage is 250 ppm The cake is soaked in water for 2-3 hrs and applied all over the pond . 2.Mahua oilcake

54. Detoxification takes about 25 days The toxicity can be reduced to 10 days through aeration and application of oxidizing agents. The other less widely use fish toxicants of plant origin are Tea seed cake – 60 ppm Tamarind seed husk – 50-100 ppm Jaggery – 1% Contd.