WATER QUALITY IN AQUACULTURE Introduction Part 1

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

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

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

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 From where? underground surface

Source well reservoir spring How much? irrigation canal stream

Source quality pasture Red tide unpopulated forested underground

Water Quality Clear water During culture Fertile water Turbid water

Water Quality Discharge Catfish pond Shrimp pond

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

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

Water temperature = active z z z = z z z inactive

Fertilization organic inorganic

Feed Marine shrimp Common carp Rainbow trout Channel catfish

Aeration Aspirator Defused air paddlewheel Pond aeration

Water exchange Salmon cages Catfish raceways Trout raceways Carp cages

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

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

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.

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

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

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

Nitrite/Nitrate feces NH4+ +1.5 O2 + Nitrosomonas NO2- + 0.5 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

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

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

Alkalinity and Hardness Alkalinity buffers against diurnal variations in pH.

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

End of Introduction Part 1 Good Water Quality = Good Harvest

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.

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.

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 32-35 ppt (parts per thousand). Brackishwater is usually water were an average human can start to taste the salt.

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.

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.

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

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

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.

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.

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.

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

Extensive management Marine shrimp

Semi-intensive management Chemical fertilizer Supplemental feeds Animal manures

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

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.

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

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

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.