Aku3201 l3
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- 1. Site Selection -Site selection is the first and generally most critical step for establishing a sustainable aquaculture facility. -In selecting a site for specific culture system both technical and non technical issues need prime consideration. -For the long term sustainability of aquaculture enterprise it is good investment sense to select an environmentally sound, low risk site at the outset. -Poor site selection can lead to failure
- 2. Site Selection • Water supply reliability and quality • Soil characteristics • Topography • Labor source • Environmental impact Sites that have access to an abundant supply of good quality water is a key to successful aquaculture enterprise
- 3. • Public utilities security • Easy communication system • Protection from natural disasters • Access to the road - Easy access for marketing - Seed supply - Room for expansion 3 Site Selection
- 4. Water Quality • Source • During culture • Discharge “Water quality issues should be taken into account at every point of the aquaculture cycle.” Dr.Claude E. Boyd
- 5. Source How much? reservoir irrigation canal stream spring well
- 6. Source quality populated Red tide underground unpopulated forested pasture
- 7. Surface vs Ground water Ground water Surface water · LLooww ttuurrbbiiddiittyy · HHiigghh ttuurrbbiiddiittyy · AAbbsseenntt ooff oorr lleessss pprreeddaattoorrss && ddiisseeaassee vveeccttoorrss · MMoorree pprreeddaattoorrss && ddiisseeaassee vveeccttoorrss · LLeessss eexxppoossuurree ttoo ccoonnttaammiinnaannttss · GGrreeaatteerr eexxppoossuurree ttoo ccoonnttaammiinnaannttss · HHiigghh mmiinneerraall ccoonntteenntt · LLooww mmiinneerraall ccoonntteenntt · LLooww oorr nnoo DDOO · DDOO pprreesseenntt · HHiigghh iirroonn,, FFee ccoonntteenntt · LLooww iirroonn ccoonntteenntt · HHiigghh hhaarrddnneessss ((mmoorree CCaa aanndd MMgg)) · LLooww hhaarrddnneessss · HHiigghheerr eexxttrraaccttiioonn ccoosstt · LLoowweerr eexxttrraaccttiioonn ccoosstt
- 8. Alternative water sources • Rainwater: free, unpredictable, only a supplement, often acidic, poorly buffered. • Municipal water: limited potential due to cost/unit volume, also contains disinfectants (e.g., chlorine). • Recycled water: conserves water, environmentally friendly, biofiltration required, high pumping cost.
- 9. Water Quality in Aquaculture The key challenge in aquaculture is to maintain high growth rates under high stocking densities without degrading the water quality. Options for gravity flow on a site should be maximized as it is efficient and cheap Poor water quality = poor harvest
- 10. Water Quality During culture Clear water Turbid water Fertile water
- 11. What is turbidity? • Optical property of water that causes light to be scattered or absorbed rather than transmitted through the water in a straight line. • Caused by suspended materials in the water such as soil particles, plankton and organic detritus. Low turbidity High turbidity
- 12. Sources of turbidity Soil erosion phytoplankton animals fish aerators deforestation
- 13. Advantages of turbidity Prevents growth of rooted aquatic plants High turbidity Low turbidity Pond water with no turbidity
- 14. Advantages of turbidity Phytoplankton turbidity provides dissolved oxygen and fish food organisms 6CO2 + 6H2O + light energy C6H12O6 + 6O2
- 15. Advantages of turbidity Lowers predation of cultured species by birds High turbidity Low turbidity
- 16. Disadvantages of turbidity Clay and soil turbidity are sometimes detrimental to fish.
- 17. Disadvantages of turbidity Overabundance of phytoplankton can be dangerous. C6H12O6 + 6O2 6CO2 + 6H2O + heat energy
- 18. Measuring turbidity Secchi Disk 30 cm
- 19. Secchi Disc Values for Aquaculture Visibility Comments < 20 cm Danger of DO problems every night 20-30 cm Plankton becoming too abundant 30-45 cm Ideal 45-60 cm Plankton becoming too scarce > 60 cm Water too clear, inadequate plankton and danger of aquatic weed problem
- 20. Water Quality Discharge Catfish pond Shrimp pond
- 21. Water quality • Different animal, different optimum water quality conditions 21
- 22. Factors that influence water quality Photosynthesis/Respiration Water temperature Fertilization Feeds Aeration Water exchange
- 23. Photosynthesis/Respiration photosynthesis 6CO2 + 6H2O + light energy C6H12O6 + 6O2 respiration C6H12O6 + 6O2 6CO2 + 6H2O + heat energy
- 24. Water temperature = = active inactive z z z z z z
- 25. Temperature • All animals have a temperature range, the ‘biokinetic range’, within which they can survive. • This range is limited by the upper and lower tolerance limit, and beyond these critical temperatures the animals may live briefly but would eventually die. • Species with wide range of tolerance - eurythermal • Species with a narrow range of tolerance – stenothermal • Eurythermal fish – Goldfish, Common Carp • Stenothermal fish – Salmonids - < 20-25°C • Temperature acts as a controlling factor regulating metabolism and thereby growth – important for aquaculturists.
- 27. Feed Common carp Marine shrimp Rainbow trout Channel catfish
- 28. Aeration Aspirator Defused air Fish mortality due To low D. O. Pond aeration paddlewheel
- 29. Water exchange Salmon cages Catfish raceways Carp cages Trout raceways
- 30. Testing Water Quality Water quality parameters often tested are: Dissolved oxygen Water temperature pH Total Ammonia Nitrogen Nitrite Alkalinity/Hardness Salinity Water test kit
- 31. How water quality values are expressed as: Parameter Value Dissolved oxygen mg/L or ppm Water temperature Degrees C or F pH Total ammonia nitrogen mg/L or ppm Nitrite mg/L or ppm Alkalinity/Hardness mg/L or ppm CaC03 Salinity g/L or ppt salt
- 32. Dissolved oxygen and water temperature dissolved oxygen and water temperature usually vary over a 24 hour cycle. Surface dissolved oxygen, mg/L Surface water temperature, C 31 29 27 6 a.m. noon 6 p.m. midnight 6 a.m. 15 10 5 0 25 summer Oxygen meter
- 33. Dissolved oxygen and water temperature Stratification can cause dissolved oxygen and temperature to vary at different depths in the same pond. Epilimnion Thermocline Hypolimnion High temperature High dissolved oxygen Low dissolved oxygen Low temperature
- 34. Dissolved Oxygen • Oxygen enters an aquatic system through: 1.Diffusion (resapan) – naturally (wind-aided) or through aeration 2.Photosynthesis 3.Entry of new water (inflow, runoff) 4.Rain
- 35. Dissolved oxygen • Atmospheric O2 enters to water through diffusion - O2 move from region of high conc. (air) to region of low conc. (water) • Faster through wind (water circulation) - Why? 35
- 36. Dissolved Oxygen (DO) • Dissolved oxygen (DO) is by far, the most important water quality parameter in aquaculture. • Like humans, fish require oxygen for respiration, survival and growth. • Oxygen consumption and DO requirement by fish increase with temperature and food consumption
- 37. Dissolved Oxygen • Biological processes that influence DO concentration in aquaculture ponds are: – Photosynthesis by green plants – Respiration by all aquatic animals
- 38. DO consumption & limits The levels of oxygen required to support life, good health and growth of aquaculture organisms vary, depending on factors such as: – species – body size – water temperature – feeding rates – stress level
- 39. DO consumption & limits Implications: • At a given temperature, smaller fish consume more oxygen per unit of body weight than larger fish - for the same total weight of fish in a tank, smaller fish require more oxygen than larger fish. • Actively swimming fish consume more oxygen than resting fish. In raceways, high exchange rates will increase energy expenditures for swimming, and oxygen consumption. • Generally, minimum DO should be greater than 5 mg/L for growth of warmwater fish and 6 mg/L coldwater fishes at their optimum temperature
- 40. Dissolved Oxygen 40 0 to 2 ppm - small fish may survive a short exposure, but lethal if exposure is prolonged. Lethal to larger fish. 2 to 5 ppm – most fish survive, but growth is slower if prolonged; may be stressful; aeration devices are often used below 3ppm. > 5 ppm to saturation – the desirable range for all.
- 41. Dissolved Oxygen • Too much oxygen – hyperoxia - gas bubble disease. • Too little oxygen – hypoxia - fish surfacing/suffocating. • Total lack of oxygen – anoxia – fish dies. • Most fish stops eating and starts dying below 30% DO saturation. • A good rule of thumb – Maintain DO levels at saturation or at least 4 ppm at all times.
- 42. Dissolved Oxygen How to prevent DO depletion at night? • Run aeration at night • Maintain Secchi disk visibility above 30-50 cm. • Use moderate stocking and feeding rates • Apply fertilizers in moderate amounts and only when needed to promote plankton blooms.
- 43. Dissolved Oxygen How to prevent DO depletion at night? • Select and manage good-quality feeds – less fines (habuk) and wastage • Exchange water • Dry out bottoms between crops and apply lime to enhance organic matter decomposition.
- 44. pH pH is a measure of acidity (hydrogen ion concentration) in water or soil. pH = - log [ H+ ] 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 neutral acid alkaline
- 45. Alkalinity and Hardness The form alkalinity takes is linked to pH of the system. . Ca(HCO3 ) 2 CaCO3 bicarbonate carbonate 4 5 6 7 8 9 10 11 pH 1.00 0.75 0.50 0.25 0.00 mole fraction H2CO3 and free CO2 HCO3 - CO3 2-
- 46. Alkalinity and Hardness Alkalinity buffers against diurnal variations in pH.
- 47. Total Ammonia Nitrogen Total ammonia nitrogen ( TAN ) is a measure of the unionized-ammonia (NH) and ammonium levels 3(NH+) in the water 4 The ratio of ammonia and ammonium varies in an equilibrium determined by pH and water temperature. 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% 7 7.4 7.8 8.2 8.6 9 9.4 9.8 pH of water as % of TAN NH3 at 20C at30C Ammonia as a % of total ammonia nitrogen
- 48. Ammonia, Nitrite, & Nitrate (cont.) • Typical pond has bacteria, which in the presence of DO converts (oxidizes) ammonia to the intermediate form of nitrite and then to nitrate. Nitrite is more toxic to fish than ammonia, however, nitrate is relatively nontoxic.
- 49. • Nitrite + haemoglobin in fish = methaemoglobin • Haemoglobin = chemical that carries oxygen throughout fish body • Methaemoglobin = will not combine with oxygen - Fish will be asphyxiated - Chocolate brown blood 49 Nitrite/Nitrate
- 50. Salinity Fresh water is less than 2 g/L Brackish water is 2 g/L to 34 g/L Sea water is more than 34 g/L NaCl
- 51. Site Selection Soil: • The site must have soils that hold water and can be compacted • Soils should contain no less than 20% clay • Soils with high sand and silt compositions may erode easily • Soil distribution, particle form and composition, uniformity, and layer thickness are equally important • Suitable soils should be close to the surface and extend deep enough that construction, harvest activity or routine pond maintenance will not cut into a water permeable layer
- 52. Site Selection Topography • Large commercial fish farms are typically built on flat land • Topography with slopes of 0-2% is better for pond construction. Extensive earth moving may be required on land with slopes greater than these; increasing construction costs.
- 53. Location -Not flood prone areas (Check 10-20 years background history ) -No earthquake, soil erosion -Far from industrial site (potential pollution- acid rain, underground water contamination) - Close to market (retail/wholesale/hypermarket) - Access to road, near to airport (for export purpose) - Access to services (water & electricity supply) -Access to communication system- telephone, internet
- 54. Labour source - Cheap & easily available - Reduce foreign labour
- 55. Environmental Impact - Consideration on environmental impact of the aquaculture establishment to the surrounding areas - No damaging impact to organism & habitat -No impact to the existing local activities (i.e. farming) (*Aquaculture project > 50 hectare require EIA)
- 56. End Good Water Quality = Good Harvest
Notas del editor
- Factors can influence on all further construction and operational decisions
- Water quality impacts on the ability to farm aquatic animals from the location of our culture facilities to the harvest of our crop. Water used to fill enclosures, ponds, tanks or cages, must be high quality. Water quality during culture must be monitored to ensure that the crop grows fast and remains healthy until harvest. Nutrient rich water discharged from culture enclosures at harvest should be controlled or treated so receiving waters are not polluted.
- The amount of water available is an important consideration when locating an aquaculture facility. Water quantity will determine the management system used to grow the crop and the crop weight that can be harvested per unit area or volume of container.
- Surface waters are usually cheap but may contain harmful nutrients, toxic chemicals or unwanted fish that compete with the farmed animals for space and food and transfer diseases to the crop. Water flowing from animal pastures, farm lands or heavily populated areas will contain more nutrients and chemicals than waters originating from forests or unpopulated areas. Ponds filled by rainfall are managed to take advantage of periods of heavy rainfall but often lack water when needed. Subsurface water pumped from wells is normally free of toxic products or unwanted fish and available on demand. However, pumping water from wells can be expensive.
- Water fertility and transparency must be considered during culture. Clear water of low fertility will provide good water quality and a healthy environment for the crop. However, crop yield per area or volume will be low because little food is available for the crop to eat. Water receiving fertilizers or feeds will be fertile, resulting in the growth of green plants, usually microscopic algae called phytoplankton, giving the water a green color. Water transparency of fertile water is lower than unfertile, clear water. Fertile water has more food for the crop to feed on and yields per area or volume will be higher than in clear water. Suspended soil particles give the water a brown color and reduce water transparency. Water carrying soil particles can enter containers after heavy rainfall. Suspended soil turbidity reduces the amount of sunlight entering the water and restricts phytoplankton growth.
- Most aquaculturists make subjective measurements of pond water appearance: Turbidity. Appearance. Color. These subjective measurements can indicate a lot about the water quality in the pond.
- External: Runoff water input which can bring in suspended soil particles. Runoff from woodland areas can bring humic turbidity. Internal: Erosion of levees. Agitation by fish and benthic animals. Plankton. Resuspension of sediment by aerators. Humic substances from manure and pond weeds.
- Water discharged from enclosures during culture or at harvest can be nutrient rich depending on the management system used. Nutrient rich effluent can increase the fertility of receiving waters, causing harm to natural vertebrate and invertebrate animal populations. Fertile discharge water should be treated before release into the environment.
- Water quality during culture is influenced by rates of photosynthesis and respiration, water temperature, levels of fertilization and feeding, mechanical aeration and the amount of water exchanged in the culture enclosure daily.
- The principal source of dissolved oxygen ( DO ) in water is photosynthesis by green plants. Additional oxygen is obtained from the atmosphere. Oxygen is released into the water as a byproduct of photosynthesis. Aquatic animals “breath” oxygen through their gills. The amount of oxygen released to the water will depend on the abundance of green plants and amount of sunshine, carbon ( CO2 ) and nutrients available for photosynthesis. Dissolved oxygen is stored in the water for use at night as photosynthesis stops in the absence of sunlight. The amount of oxygen stored in freshwater depends on water temperature and atmospheric pressure. Cold water and high atmospheric pressure found at sea level stores more dissolved oxygen than warm water and low atmospheric pressure found at high elevations. Saltwater holds less dissolved oxygen than freshwater at equivalent temperature and atmospheric pressure. All plants and animals respire 24 hours a day. Respiration uses the oxygen generated during photosynthesis and releases carbon dioxide ( CO2 ) into the water. A healthy aquatic environment has a balance between photosynthesis and respiration to maintain enough dissolved oxygen for the respiratory needs of the plants and animals and carbon dioxide for photosynthesis. Sometimes in fertile water with abundant phytoplankton, the amount of oxygen used during respiration by the plants and animals is greater than the amount of oxygen stored in the water. Dissolved oxygen declines to unhealthy concentrations at night and partial or complete mortality of the crop can occur. Learning to maintain adequate levels of dissolved oxygen during culture is important for the farmer that wants a good harvest.
- Fish are cold blooded and their body temperature is determined by water temperature. Fish in warm water are active and grow rapidly with adequate food. Fish in cold water are sluggish and growth slows or stops. The metabolic rate of aquatic plants and animals slows during the winter when water temperatures are cold. Respiration rate declines and the amount of dissolved oxygen required by the plants and animals lowers. During the summer, respiration rates of the plants and animals are high and dissolved oxygen consumption increases. As noted, water holds more dissolved oxygen when water temperature is low. Thus, maintaining good water quality is easier in the winter than in the summer when farmed animals are actively feeding and growing rapidly.
- Fertilizers are added to water to increase the abundance of green plants. Green plants are the base of an aquatic food chain that expands as the abundance of green plants increases. More aquatic foods are available for the farmed animals to consume and harvest is increased. However, excessive fertilization leads to an overabundance of phytoplankton and declining water quality. The amount of fertilizer applied per unit area of enclosure should be controlled to maintain good water quality.
- When natural foods no longer supply enough nutrition for rapid growth of the cultured organisms, feeds are provided to maintain good growth. Feeding the aquatic crop will increase the weight of animals harvested. However, fish wastes and uneaten feed increase water fertility, leading to heavy phytoplankton populations and deteriorating water quality. The amount of feed fed daily per unit area or volume of container must be controlled to ensure good water quality during the culture period.
- Water fertilization and feeding of the animals lead to poor water quality. Low dissolved oxygen ( DO ) is the first sign the water quality is deteriorating. Dissolved oxygen concentration is increased with mechanical aeration of the water. Numerous methods of mechanical aeration are available to aquaculturists. Mechanical aeration introduces atmospheric oxygen into the water, increasing dissolved oxygen levels. Mechanical aeration permits higher daily feeding rates than in unaerated enclosures, leading to increased yields.
- Daily feeding rates can increase to levels that cause water quality to deteriorate even with mechanical aeration. Fish growth will slow or stop due to the stress caused by poor water quality. Exchanging nutrient loaded water with clean water will flush excess nutrients from the enclosure and improve water quality. Concrete tanks ( raceways ) and floating cages with constant water exchange will allow high daily feeding rates and highest yields per unit of enclosure volume of any management system.
- Water quality is monitored on a regular basis. Water quality test kits or battery operated test equipment can be purchased to measure the water quality parameters listed above.
- Dissolved oxygen, total ammonia nitrogen, nitrite, alkalinity and hardness are measured in milligrams per liter or parts per million . Salinity is measured in grams per liter or parts per thousand salt. Water temperature is measured in degrees Celsius or Fahrenheit. pH is given a numerical value between 0 and 14.
- Dissolved oxygen is strongly influenced by photosynthesis. Thus, dissolved oxygen concentrations are highest during the day when photosynthesis is active and drops during the night when photosynthesis stops and consumption by plants and animals continues. Highest dissolved oxygen concentrations are measured in late afternoon and lowest concentrations are found at daybreak. Water Temperature is also strongly influenced by solar radiation and is highest during the day and lowest at night. A dissolved oxygen meter with thermometer is used to quickly measure dissolved oxygen concentration and water temperature.
- Thermal stratification in deep ponds can cause dissolved oxygen and water temperature to vary with depth. Water density increases with decreasing water temperature until 40C ( 390F ). Surface waters absorb heat from the sun during warm summer months. As the surface water warms, the water density decreases and surface water will float above the cooler, deeper, bottom water. The difference in water temperatures between surface and bottom water becomes great enough to stop the surface and bottom water layers from mixing and the pond becomes stratified. The warm surface water layer, Epilimnion, is high in DO due to photosynthetic activity. The cool bottom water layer, Hypolimnion, has little or no DO because little sunlight is available for photosynthesis. The Epilimnion and Hypolimnion are separated by a layer of water with rapidly dropping water temperatures called the Thermocline. The surface water will mix with the bottom water when surface water temperature approaches bottom water temperature due to cooling air temperature, heavy, cool rainfall and/or a strong wind to force mixing. Rapid mixing of surface and bottom water layers is called a “turnover” and can cause surface water DO to drop to concentrations that kill fish.
- Why? Because wind stirs up waves and creates currents that increase both the amount of water surface that is in contact with air Mixes oxygenated water throughout the pond
- pH is a measure of acidity in water and soil. Waters with a pH below 7 have a high hydrogen ion concentration and are termed acid and water with a pH above 7 has a low hydrogen ion concentration and are termed alkaline. Water with a pH between 6.5 and 8 are best for aquaculture. Water with a ph below 5 or above 10 are detrimental to aquaculture.
- Water with a pH of 7 is considered neutral or water that is neither acid nor alkaline. Carbon dioxide is acidic and lowers pH as the amount of carbon dioxide in the water increases. As pH increases from 7, bicarbonate is formed and the water becomes slightly alkaline. At a pH of 8.3, bicarbonate concentration reaches its highest level and free carbon dioxide ( CO2 ) reaches zero. As pH continues to raise, carbonate becomes the dominant source of alkalinity in most waters. pH fluctuates depending on the amount of free carbon dioxide found in the water. pH increases when carbon dioxide is removed from the water by photosynthesis and decreases when carbon dioxide is added to the water by respiration, especially at night when photosynthesis has stopped. Hardness is not influenced by pH.
- Alkalinity buffers against large changes in diurnal pH variation. Photosynthesis activity is strong in fertile aquaculture ponds with a heavy phytoplankton population or bloom. During photosynthesis carbon dioxide is removed from the water and alkalinity will increase. Waters with high concentrations of bicarbonates and carbonates will only have a moderate increase in alkalinity because the bicarbonate and carbonates will disassociate in the absence of free carbon dioxide to produce more carbon dioxide that can be used by plants during photosynthesis. Waters with little alkalinity have low concentrations of bicarbonate and carbonate
- Total ammonia nitrogen is commonly measured in water used for aquaculture. Total ammonia nitrogen is the sum of unionized and ionized ammonia in the water. Unionized-ammonia is very toxic to aquatic animals while ionized ammonia has slight toxicity. Unionized-ammonia ( NH3 ) is a nitrogenous excretory product of most aquatic animals. Fish excrete unionized-ammonia through their gills. Most unionized-ammonia is ionized to ammonium ( NH4+ ) upon contact with water. The amount of unionized-ammonia ionized to ammonium will depend on water pH and temperature. The amount of unionized-ammonia found in water as a percentage of total ammonia nitrogen will increase with increases in pH and water temperature ( graph above ). Thus, warm, high alkalinity water can result in high concentrations of unionized ammonia if total ammonia concentrations are high. As little as 0.05 mg/l unionized ammonia can be toxic to aquatic animals.
- Salinity is the total concentration of all ions in water. Most salinity is attributed to sodium chloride but other ions also contribute to salinity. Fresh water has a salinity of less than 2 g/l ( 2 ppt ) and sea water has a salinity of greater than 34 g/l. Brackish water is a mixing of fresh and sea waters and salinity can range from 2 to 34 g/l. Matching the aquacultured animal to its ideal salinity is important for good growth and survival. Most organisms evolved in fresh water will not survive in seawater and visa versa.
- Understanding water quality and how it impacts on aquatic farming is important for maximizing yields. Poor water quality will reduce crop yields and lower profits. Daily monitoring of water quality provides evidence that the aquatic environment is within the tolerance ranges of the culture animal and a bountiful harvest is expected.