To a great extent water quality determines the success or failure of a fish farming operation

WATER IN AQUACULTURE SYSTEMS

Fish perform allbodily functions in water

• Eat

• Breathe

•

•

• Take in and lose salts

WATER IN AQUACULTURE SYSTEMS

Water Balance in Freshwater Fish

Salts

Large quantitiesof dilute urine

Ammonia

Water

Water Balance in Saltwater Fish

Small quantities ofconcentrated urine

Ammonia

Water

Drinkssea water

Water Resources

• Water quality

• Water quantity

• Water sources

Inadequate water quality causes more Inadequate water quality causes more losses than any other problem!losses than any other problem!

WATER IN AQUACULTURE SYSTEMS

Physical

Temperature

• •

Chemical (“No effect” limits)

Physical Characteristicsof Water

•

• “Universal solvent”

–

WATER IN AQUACULTURE SYSTEMS

Dissolved Oxygen

• Importance– highest cause of mortality

• Solubility– variables

•

•

•

• Safe levels– > 5mg/l

7

6

5

4

3

2

1

05 pm 10 pm 5 am

Measured values

Projected values

mg/l

Projected Dissolved Oxygen Levels for Ponds

Uniform dissolved O in pond2

Decomposingmaterials

Low dissolvedoxygen (cool)

High dissolvedoxygen (warm)

Low dissolved oxygen - possible fish kill

TurnoverTurnover

Relationships

Temperature (F) (pH) 7.0 8.09.0

50 0.19 1.8315.7

68 0.40 3.8228.4

86 0.80 7.4644.6

Percent Ammonia

Percent of Total Ammoniain the Un-Ionized Form at

Various Temperatures and pH

Nitrification

NONO33-- NHNH33

1½ O1½ O22

nitrosomonas nitrosomonas nitrobacter nitrobacter

1½ O1½ O22 NONO22

--

• Requires 3 moles oxygen to convert one mole of ammonia to nitrate

•

Dissolved Gasses

• Problem gasses– Nitrogen (primarily)

•

• Problem sources – Wells and Springs

–

– leaky pipeleaky pipe

Popeye/exophthalmiaPopeye/exophthalmia

dorsal viewdorsal view

WATER IN AQUACULTURE SYSTEMS

Water quantity parameters 

• Requirements are based on temperature-dependent 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•   •  

Pre-Use treatment

Sediment removal•  Settling basin/pond –

•  Filtration –

Gas stabilization (O2 and/or N2)•  Slatted inflow boards• • 

WATER IN AQUACULTURE SYSTEMS

Pre-Use treatmentSterilization

•  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 IN AQUACULTURE SYSTEMS

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 filtersduring harvesting–

–

0.8

0.6

0.4

0.2

0.02 6 10 14 18 22

8

6

4

2

0

Ammonia(mg/l)

Nitrites &Nitrates(mg/l)

NHNO

NO

23

3

Time in Days

Time Requiredfor Bio-Filter to Mature