1. WATER QUALITY IN AQUACULTURE Introduction
Part 1

2. Aquaculture and Seafood
Capture from the oceans is maximized.
Aquaculture is growing as a source of the world’s seafood supply.

3. Benefits of Aquaculture
Asian fresh seafood market
Ability to bring fresh, or even live, seafood to market at a specific time and quantity.
US seafood market

4. Aquaculture is based on water
The key to the successful culture of aquatic organisms is maintenance of water quality.
Poor water quality = poor harvest.
Fish ponds in China

5. 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

6. Source
From where?
underground
surface

7. Source
well
reservoir
spring
How much?
irrigation canal
stream

8. Source quality pasture Red tide unpopulated forested underground

9. Water Quality
Clear water
During culture
Fertile water
Turbid water

10. Water Quality
Discharge
Catfish pond
Shrimp pond

11. Factors that influence water quality
Photosynthesis/Respiration
Water temperature
Fertilization
Feeds
Aeration
Water exchange

12. Photosynthesis/Respiration
6CO2 + 6H2O + light energy  C6H12O6 + 6O2
respiration
C6H12O6 + 6O2  6CO H2O + heat energy

13. Water temperature =
active z z z = z z z
inactive

14. Fertilization
organic
inorganic

15. Feed
Marine shrimp
Common carp
Rainbow trout
Channel catfish

16. Aeration
Aspirator
Defused air
paddlewheel
Pond aeration

17. Water exchange
Salmon cages
Catfish raceways
Trout raceways
Carp cages

18. Testing Water Quality Water quality parameters often tested are:
Dissolved oxygen
Water temperature pH
Total Ammonia Nitrogen
Nitrite/Nitrate
Alkalinity/Hardness
Salinity
Water test kit

19. How water quality values are expressed
Parameter
Value
Dissolved oxygen
mg/L O2
Water temperature
C (Celsius) pH
Total ammonia nitrogen
mg/L N
Nitrite
mg/L NO2-
Nitrate
mg/L NO3-
Alkalinity/Hardness
mg/L CaCO3
Salinity
g/L salt

20. Dissolved oxygen and water temperature
Oxygen meter
dissolved oxygen and water temperature usually vary over a 24 hour cycle.
Surface dissolved oxygen, mg/L
Surface water temperature, C 15 31 29 10
summer 27 5 25
6 a.m.
noon
6 p.m.
midnight
6 a.m.

21. Dissolved oxygen and water temperature
Stratification can cause dissolved oxygen and temperature to vary at different depths in the same system.
Epilimnion
Thermocline
Hypolimnion
High temperature
High dissolved oxygen
Low dissolved oxygen
Low temperature

22. pH
pH is a measure of acidity (hydrogen ion concentration) in water or soil.
pH = - log [ H+ ] 1 2 3 4 5 6 7 8 9 10 11 12 13 14
neutral
acid
alkaline

23. Total Ammonia Nitrogen
Total ammonia nitrogen ( TAN ) is a measure of the ammonia (NH3) and ammonium levels (NH4+) in the water
The ratio of ammonia and ammonium varies in an equilibrium determined by pH and water temperature.
Ammonia as a % of total ammonia nitrogen

24. Nitrite/Nitrate
feces
NH O2 + Nitrosomonas NO O2 + Nitrobacter NO3-
Nitrites and nitrates are produced by an aerobic bacterial nitrification process of ammonia by Nitrosomonas and Nitrobacter respectively.
Nitrites are toxic to aquatic organisms, usually by being actively transported across the gills to bind with hemoglobin (making methemoglobin) which is incapable of transporting oxygen. (note: nitrites are usually not a problem in salt water systems)
Nitrates are usually not toxic unless in very high concentrations.
Bacterial
decomposition

25. Alkalinity and Hardness
Total titratable bases
Total divalent salts
HCO3-
bicarbonate
CO23-
carbonate
calcium
magnesium
Ca2+
Mg2+
Calcium bicarbonate
Calcium carbonate
CaCO3
Magnesium
bicarbonate
Mg( HCO3 )2
Magnesium
carbonate
Mg CO3
Ca( HCO3 )2

26. Alkalinity and Hardness
The form alkalinity takes is linked to pH of the system.

27. Alkalinity and Hardness
Alkalinity buffers against diurnal variations in pH.

28. Salinity NaCl Brackish water is 2 g/L to 34 g/L
Freshwater is less than 2 g/L
Sea water is more than 34 g/L
NaCl

29. End of Introduction Part 1
Good Water Quality = Good Harvest

30. WATER QUALITY IN AQUACULTURE Introduction
Part 2: Applications
This is the second “basics” unit for the water quality course. The first unit gave an overview of what water quality is and how it can be measured. This unit gives a preliminary description of how aquaculture systems are classified, how this related to water quality and other issues related to water quality and aquaculture.

31. Classification of aquaculture systems
Salinity of culture water.
Producer/consumer relationship.
Type of culture unit.
Species
Management intensity
The expected water quality parameters are greatly influenced by the classification the culture system falls in to. Each of these major points is discussed in more detail in the following slides.

32. Salinity
Freshwater has a low ionic concentration (i.e. streams, rivers, ponds and lakes).
Saltwater has a high ionic concentration (ocean waters).
Brackishwater has an ionic concentration between freshwater and saltwater ( mangroves ).
Fresh water and salt water are usually easy to identify, with brackishwater falling in between (and is difficult to define as a specific level of salt). Fresh waters may have a salinity level, but usually one so low that it would take a chemical test to identify it. Full strength seawater usually falls between ppt (parts per thousand). Brackishwater is usually water were an average human can start to taste the salt.

33. Producer/consumer relationship
Commercial
aquaculture
Subsistence
Commercial operations are primarily for sales and not personal consumption. Commercial operators usually do regularly test water quality parameters and take active measures to maintain water quality (aerators, etc.). Subsistence refers to a pond or culture system that is primarily for personal use and does not provide a significant excess sales. Such operations usually do not do any formal water quality checks, although managers may become adept at spotting water quality problems by observing behavior of the cultured organism. Water quality is maintained through use of fertilizers (usually manure), flushing of water and manipulation of feeding regimes. In most cases the definition of a subsistence and commercial size is dependent on where the operations take place. In a poor area, a 1000 meter squared pond might be considered commercial, where in a more prosperous area it would be considered subsistence.

34. Type of culture unit
Many different culture units are used to grow aquatic organisms.
The culture unit selected is based on economic, space and water concerns.
The type and size of the culture unit will determine water quality management.
Following slides will detail some of the different types of culture units. The type of culture unit used is often dictated by water quality concerns. For example, an operation that has a abundant supply of good quality water may use a flow through system (such as raceways), where an operation that has limited supplies may use a static water system (such as a pond). Some operations use natural water bodies (with cage or pen systems) for aquaculture. In cases such as these, managers are more concerned with not degrading water quality unnecessarily, particularly in the area the operation is located.

35. Type of culture unit: Earthen Pond Levee ponds Reservoir Pond
Pond culture is one of the most common ways that aquatic organisms are grown. Pond culture systems may be as simple as a hand excavated earthen pond, to machine excavated large ponds. Most often, particularly in areas with the proper soil type, ponds are unlined. In other areas, commercially available pond liners can be used to prevent seepage. Ponds are most often used in areas where large quantities of a commercially valuable species are grown and land costs are not prohibitive.
Levee ponds
Reservoir Pond

36. Type of culture unit: Cage/Pen
Cages in lake
Cages in ocean
Cage and pen systems are used for intensive culture of aquatic organisms in a general water body. These systems may be used to ease harvest, separate different species in a polyculture environment or share a common water resource (such as culture in natural water bodies). Although each cage or pen unit may not have individual water quality concerns, the water quality of the water body as a whole, or the area around the cage/pen system, may be of concern. (Density of the organism can significantly affect the water quality in the immediate area of the organism i.e. dissolved oxygen.)
Pen

37. Type of culture unit: Tank
Rectangular tank
Circular tank
In areas where space limitations may require high density culture, or in situations such as a hatchery, tanks or silos can be used. This is usually reserved for situations where the organism is highly valuable. In artificial culture systems such as these, water quality management is critical and almost entirely under the control of the manager. Water exchange (where possible) can often be used to correct water quality problems quickly.

38. Trout farms using raceways
Raceway culture
Trout farms using raceways
Raceways are usually reserved for operations that have an abundance of good quality water. Water is usually flowed a single time through the culture system (one use) although it is possible to construct several raceways in series to use the same water. Using raceways in series requires the manager to calculate the degradation of water quality through each system (this requires knowledge of the initial water quality, species and feeding level for proper water quality estimation at each stage). In comparison to pond and cage systems, raceways are fairly expensive to construct, but may be attractive due to the ability to maintain high water quality.

39. Species
The species cultured will determine stocking density, water quality levels desired and the most appropriate system to use.
What is actually going to be grown in an aquaculture operation is important for classification of the aquaculture system and water quality concerns. Fish, crustaceans, molluscs, etc. each have different water quality limitations. The species used will often determine the appropriate system chosen and the type of water quality management needed. For example, tilapia is much more tolerant of poor water quality than shrimp in a hatchery situations.

40. Management intensity
Levels of aquaculture management are closely tied to water quality.
Extensive management – no control of water quality
Semi-intensive management – some control of water
quality
Since water quality is the so important in aquaculture, it is no surprise that specific water quality concerns often help classify management intensity. Different management intensity levels usually hinge on a specific water quality parameter that is affected.
Intensive management – control of water quality

41. Extensive management
Marine shrimp

42. Semi-intensive management
Chemical fertilizer
Supplemental feeds
Animal manures

43. Water exchange in tanks Nutritionally complete
Intensive management
Aeration in ponds
Water exchange in tanks
Nutritionally complete
pelleted feeds

44. Public perceptions of aquaculture
Water quality concerns:
Water pollution
Salinization
Sedimentation
Spread of disease
Other concerns:
Wetland destruction
Wasteful of resources
Biodiversity
Land conversion
Social impacts
There appears to be a clear link between the acceptance of agricultural operations and the public perceptions of how environmentally friendly they are. For example, in pork operations, public reaction to the problems of odor and manure effluent have led to strict restrictions for pork producers in America. The acceptance and growth of aquaculture operations will have to take into account the public and its reactions to real and perceived issues related to aquaculture. Most often laws and regulations are enacted after the public complains to their representatives about a real or perceived problem with an industry. In this case a knowledge of water quality can help prevent problems and allow a manager to address the public’s questions about the effect an aquaculture operation can have on water quality and other issues.
(Some of the common complaints about aquaculture as detailed by Dr.Claude E.Boyd.) These complaints are closely linked to the increased awareness of the protection and quality of the environment. In general, Dr.Boyd has addressed all of these complaints, pointing out that while aquaculture has had environmental issues from time to time, that the nature of aquaculture requires that environmental concerns be addressed promptly. Water quality complaints in particular will be discussed briefly in the following slides, as will other concerns.

45. Water quality concerns
It is good management to keep water quality standards throughout the production cycle, even when water is to be released into the natural environment. Treatment of water prior to discharge (through remediation or conditioning ponds) can be used to reduce problems associated with discharge. In high density operations obtaining water from a common source, untreated effluent from one operation can cause problems for another operation downstream. Even in areas where there are no regulations or laws that mandate effluent standards, maintaining minimum effluent standards is probably a wise choice from a management and public relations standpoint.
Cages in Indonesia
Shrimp pond effluent
in Thailand

46. Preservation of saltwater mangrove Preservation of freshwater wetlands
Other concerns
Preservation of saltwater mangrove
Aquaculture operations, in general, have a lower FCR (Feed conversion rate, or amount of food fed to gain weight in an animal [lower FCR is desirable]) and allow greater density than any land based livestock enterprise (due to the three dimensional nature of aquatic culture). As with any industry, economics plays a large role in determining what type of agriculture a producer will engage in. The aquaculture industry has been increasing worldwide annually due to the increasing demand and reduced wild supply. As culture techniques improve and seafood prices increase, it can be expected that aquaculture will continue to be a growing industry. Just as in any industry, there have been some problems and setbacks, such as the destruction of mangrove forests for shrimp farms (before it was found that these areas were unsuitable for culture), but it can be expected that as knowledge increases problems will be identified and solved. Keeping in mind public reaction to any new aquaculture enterprise before it is started may help a manager prevent problems before they start.
Preservation of freshwater wetlands

47. End
This unit is left intentionally shorter to allow discussion about how water quality concerns might have an effect on the social, political, economic and environmental aspects of aquaculture.