WATER IN AQUACULTURE SYSTEMS
To a great extent
water quality
determines the
success or failure
of a fish farming
operation
WATER IN AQUACULTURE SYSTEMS
Fish perform all
bodily functions in water
• Eat
• Breathe
•
•
• Take in and lose salts
Water Balance in Freshwater Fish
Water
Salts
Ammonia
Large quantities
of dilute urine
Water Balance in Saltwater Fish
Water
Drinks
sea water
Ammonia
Small quantities of
concentrated urine
Water Resources
• Water quality
• Water quantity
• Water sources
Inadequate water quality causes more
losses than any other problem!
WATER IN AQUACULTURE SYSTEMS
Physical
Temperature
•
•
Chemical (“No effect” limits)
WATER IN AQUACULTURE SYSTEMS
Physical Characteristics
of Water
•
• “Universal solvent”
–
Dissolved Oxygen
• Importance
– highest cause of mortality
• Solubility
– variables
•
•
•
• Safe levels
– > 5mg/l
Projected Dissolved Oxygen
Levels for Ponds
7
Measured values
6
5
mg/l
4
Projected values
3
2
1
0
5 pm
10 pm
5 am
Uniform dissolved O in pond
2
High dissolved
oxygen (warm)
Low dissolved
oxygen (cool)
Decomposing
materials
Turnover
Low dissolved oxygen possible fish kill
Relationships
Percent of Total Ammonia
in the Un-Ionized Form at
Various Temperatures and pH
Percent Ammonia
Temperature (F)
(pH) 7.0
8.0
9.0
50
0.19
1.83
15.7
68
0.40
3.82
28.4
86
0.80
7.46
44.6
Nitrification
NH3
1½ O2
nitrosomonas
NO2-
1½ O2
nitrobacter
NO3-
• Requires 3 moles oxygen to convert one mole of
ammonia to nitrate
•
Dissolved Gasses
• Problem gasses
– Nitrogen (primarily)
dorsal view
•
• Problem sources
– Wells and Springs
–
–
Popeye/exophthalmia
leaky pipe
WATER IN AQUACULTURE SYSTEMS
Water quantity parameters
• Requirements are based on temperaturedependent and size-dependent standard
metabolic rates for fish
•
WATER IN AQUACULTURE SYSTEMS
Water quantity parameters
Suggested replacement times
Linear
• Noncirculating –
• Circulating
Suggested water velocity rates
• Noncirculating –
• Circulating -
WATER IN AQUACULTURE SYSTEMS
Water quantity parameters
Flow measuring techniques
Flow meters
•
•
Pond filling time – not very accurate
WATER IN AQUACULTURE SYSTEMS
Water quantity parameters
Weir gauges
• Sharp-crested – if outfall consists of dam
boards
• V-notch
• Trapezoidal
•
•
WATER IN AQUACULTURE SYSTEMS
Pre-Use treatment
Sediment removal
• Settling basin/pond –
• Filtration –
Gas stabilization (O2 and/or N2)
• Slatted inflow boards
•
•
WATER IN AQUACULTURE SYSTEMS
Pre-Use treatment
Sterilization
• Ultraviolet –
•
• Chlorination-de-chlorination –
•
Temperature control
• Heating
• Chilling
WATER IN AQUACULTURE SYSTEMS
Water utilization
• Open water systems
• Flow-through
-Water enters pond or series of ponds and
exits with/without treatment
-
Water Sources
•
•
• Rivers, lakes and streams
• Surface
•
•
Springs
• Advantages
–
– few or no predators
– no pathogens
• Disadvantages
–
Wells
• Types
–
–
• Advantages
– no predators
– no pathogens
• Disadvantages
–
– low O2
Rivers, Lakes and Streams
• Advantages
– large volumes
– inexpensive
• Disadvantages
–
– excessive nutrients
Surface
• Advantages
– inexpensive
• Disadvantages
– contaminates
–
– 5-7 acre watershed
per surface acre of
water
Groundwater
• Advantages
–
• Disadvantages
– hard to drain
•
• removal of fish
Municipal
• Advantages
–
– no predators
–
• Disadvantages
– disinfectants
•
• chloramines
–
Water Quantity
•
•
•
•
Ponds
Raceways
Cages
Recirculating aquaculture systems
Ponds
• Minimum requirement
– 13 gal/min or 50L/min per
acre
• Rational
–
– to replace evaporation
–
Raceways
• Minimum requirement
– 500 gal/min. or 1900L/min
• Rational
–
–
Recirculating Aquaculture Systems
• Minimum requirement
– varies depending on size
of system
–
• Rational
– needed to backflush filters
during harvesting
–
–
Time Required
for Bio-Filter to Mature
0.8
8
NO 3
0.6
Ammonia
(mg/l)
NO2
NH 3
6
0.4
4
0.2
2
0.0
0
2
6
10
14
Time in Days
18
22
Nitrites &
Nitrates
(mg/l)