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
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
• 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
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
Source
How much?
reservoir
irrigation canal
stream
spring
well
Sourcequality
populated
Red tide
underground
unpopulated
forested
pasture
Surface vs Ground water
Ground water Surface water• Low turbidityLow turbidity • High turbidityHigh turbidity
• Absent of or less predators & Absent of or less predators & disease vectorsdisease vectors
• More predators & disease More predators & disease vectorsvectors
• Less exposure to contaminantsLess exposure to contaminants • Greater exposure to Greater exposure to contaminantscontaminants
• High mineral contentHigh mineral content • Low mineral contentLow mineral content
• Low or no DOLow or no DO • DO presentDO present
• High iron, Fe contentHigh iron, Fe content • Low iron contentLow iron content
• High hardness (more Ca and Mg)High hardness (more Ca and Mg) • Low hardnessLow hardness
• Higher extraction costHigher extraction cost • Lower extraction costLower extraction cost
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.
Water Quality in AquacultureThe 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 cheapPoor water quality = poor harvest
Water Quality
During culture
Turbid water
Clear water
Fertile water
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
Sources of turbiditySoil erosion
phytoplankton
animals
fish
aerators
deforestation
Advantages of turbidity
Prevents growth
of rooted
aquatic plants
High turbidity
Low turbidity
Pond water with no turbidity
Phytoplankton turbidity provides dissolved oxygen and fish food organisms
Advantages of turbidity
6CO2 + 6H2O + light energy C6H12O6 + 6O2
Lowers predation of cultured species by birds
Advantages of turbidity
High turbidityLow turbidity
Disadvantages of turbidityClay and soil turbidity are sometimes
detrimental to fish.
Overabundance of phytoplankton can be dangerous.
Disadvantages of turbidity
C6H12O6 + 6O2 6CO2 + 6H2O + heat energy
Measuring turbidity
Secchi Disk
30 cm
Secchi Disc Values for AquacultureVisibility 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
Water QualityDischarge Catfish pond
Shrimp pond
• Different animal, different optimum water quality conditions
Water quality
21
Factors that influence water quality
Photosynthesis/Respiration
Water temperature
Fertilization
Feeds
Aeration
Water exchange
Photosynthesis/Respiration
6CO2 + 6H2O + light energy C6H12O6 + 6O2
photosynthesis
respiration
C6H12O6 + 6O2 6CO2 + 6H2O + heat energy
Water temperature
=
=
active
inactive
z z z
zzz
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.
Fertilization
organic inorganic
FeedCommon carp
Marine shrimp
Rainbow trout
Channel catfish
AerationAspirator
Defused air
Pond aeration paddlewheel
Fish mortality dueTo low D. O.
Water exchange
Salmon cages
Carp cages
Catfish raceways
Trout raceways
Testing Water QualityWater quality parametersoften tested are:
Dissolved oxygenWater temperaturepHTotal Ammonia NitrogenNitriteAlkalinity/HardnessSalinity
Water test kit
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
Dissolved oxygen and water temperature
dissolved oxygen and water temperature usually vary over a 24 hour cycle.
6 a.m. 6 a.m.midnight6 p.m.noon
0
15
10
5
Surface dissolved oxygen, mg/L
25
27
29
31
Surface water temperature, C
summer
Oxygen meter
Stratification can cause dissolved oxygen and temperature to vary at different depths in the same pond.
Dissolved oxygen and water temperature
Epilimnion
Thermocline
Hypolimnion
High temperature
High dissolved oxygen
Low dissolved oxygen
Low temperature
Dissolved Oxygen• Oxygen enters an aquatic system through:
1.Diffusion (resapan) – naturally (wind-aided) or through aeration
2.Photosynthesis3.Entry of new water (inflow,
runoff)4.Rain
• 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?
Dissolved oxygen
35
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
Dissolved Oxygen• Biological processes that influence DO
concentration in aquaculture ponds are:
– Photosynthesis by green plants
– Respiration by all aquatic animals
DO consumption & limitsThe 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
DO consumption & limitsImplications:
• 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
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.
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.
Dissolved OxygenHow 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.
Dissolved OxygenHow 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.
pH = - log [ H+ ]
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14
acid alkaline
pH pH is a measure of acidity (hydrogen ion
concentration) in water or soil.
neutral
.
4 5 6 7 8 9 10 11
pH
0.00
0.25
0.50
0.75
1.00
mo
le f
rac
tio
n
H2 CO3 and
free CO2HCO3
-CO3
2-
bicarbonate carbonate
Ca(HCO3 ) 2 CaCO3
Alkalinity and HardnessThe form alkalinity takes is linked to pH of the system.
Alkalinity and HardnessAlkalinity buffers against diurnal variations in pH.
Total Ammonia Nitrogen Total ammonia nitrogen ( TAN ) is a measure of the unionized-ammonia (NH3) and ammonium levels (NH4
+) in the waterThe ratio of ammonia and ammonium varies in an equilibrium determined by pH and water temperature.
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
7
7.4
7.8
8.2
8.6 9
9.4
9.8
pH of water
NH 3
as
% o
f T
AN
at 20C
at30C
Ammonia as a % of total ammonia nitrogen
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.
• 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
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
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
Site Selection
Site SelectionTopography
• 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.
-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
Location
- Cheap & easily available
- Reduce foreign labour
Labour source
- 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)
Environmental Impact
End
Good Water Quality = Good Harvest
Recommended
