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 pasture quality Red tide unpopulated forested underground populated
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 photosynthesis 6CO2 + 6H2O + light energy C6H12O6 + 6O2 respiration C6H12O6 + 6O2 6CO2 + 6H2O + heat energy
Water temperature = active z z z = z z z inactive
Fertilization inorganic organic
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
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 31 15 29 10 summer 27 5 25 0 6 a.m. noon 6 p.m. midnight 6 a.m.
High temperature High dissolved oxygen Epilimnion Thermocline Low dissolved oxygen Low temperature Hypolimnion Dissolved oxygen and water temperature Stratification can cause dissolved oxygen and temperature to vary at different depths in the same system.
pH pH is a measure of acidity (hydrogen ion concentration) in water or soil. pH = - log [ H+ ] 2 6 14 0 1 3 4 5 7 8 9 10 11 12 13 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 NH4++1.5 O2 + Nitrosomonas NO2- + 0.5 O2 + Nitrobacter NO3- feces Bacterial decomposition
bicarbonate carbonate HCO3- CO23- Calcium carbonate Magnesium bicarbonate Magnesium carbonate CaCO3 Mg CO3 Mg( HCO3 )2 Alkalinity and Hardness hardness alkalinity Total titratable bases Total divalent salts calcium magnesium Ca2+ Mg2+ Calciumbicarbonate 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 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 AQUACULTUREIntroduction Part 2: Applications
Classification of aquaculture systems • Salinity of culture water. • Producer/consumer relationship. • Type of culture unit. • Species • Management intensity
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 ).
Producer/consumer relationship • Commercial aquaculture • Subsistence aquaculture
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.
Type of culture unit: Earthen Pond Leveeponds Reservoir Pond
Type of culture unit: Cage/Pen Cages in lake Cages in ocean Pen
Type of culture unit: Tank Rectangular tank Circular tank
Raceway culture Trout farms using raceways
Species • The species cultured will determine stocking density, water quality levels desired and the most appropriate system to use.
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 Intensive management – control of water quality
Extensive management Marine shrimp
Semi-intensive management Chemical fertilizer Supplemental feeds Animal manures
Intensive management Aeration in ponds Water exchange in tanks Nutritionally complete pelleted feeds
Water quality concerns: Water pollution Salinization Sedimentation Spread of disease Other concerns: Wetland destruction Wasteful of resources Biodiversity Land conversion Social impacts Public perceptions of aquaculture
Water quality concerns Cages in Indonesia Shrimp pond effluent in Thailand
Other concerns Preservation of saltwater mangrove Preservation of freshwater wetlands