Aquaculture Systems Operation & Maintenance David Crisostomo DC Aquatic Systems Cooperative Extension Service University of Guam

Operation Understanding Water Quality Water quality is critical for successful culture of aquatic organisms Water quality is critical for successful culture of aquatic organisms All parameters interact with each other very quickly. All parameters interact with each other very quickly. Some can be controlled, others are subject to the outside environment….such as temperature and rainfall. Some can be controlled, others are subject to the outside environment….such as temperature and rainfall.

Water Quality Parameters Dissolved Oxygen - Enters water from 3 main sources… Dissolved Oxygen - Enters water from 3 main sources… Diffuse through the surface of the water- natural Diffuse through the surface of the water- natural From agitation or aeration-mechanical From agitation or aeration-mechanical From submerged aquatic plants….not floating plants-biological From submerged aquatic plants….not floating plants-biological

Dissolved Oxygen Cycle Level of DO is function of light, water quality and nutrient level. Level of DO is function of light, water quality and nutrient level. Natural diurnal fluctuation Natural diurnal fluctuation

Process of O2 transfer Oxygen molecules are diffused into the water at the air/water interface. This interface occurs around an air bubble and/or around a droplet of water. Oxygen molecules are diffused into the water at the air/water interface. This interface occurs around an air bubble and/or around a droplet of water. More O2 is transferred with smaller bubbles or water droplets per unit of energy. More O2 is transferred with smaller bubbles or water droplets per unit of energy. More transfer happens if partial pressure differentials are high. More transfer happens if partial pressure differentials are high.

Dissolved Oxygen Several factors affect the solubility of oxygen in water…elevation, temperature and barometric pressure. Higher temp and higher elevation decrease oxygen solubility (amount of O2 the water can hold). You can predict the solubility with the D.O. calculator at this site Several factors affect the solubility of oxygen in water…elevation, temperature and barometric pressure. Higher temp and higher elevation decrease oxygen solubility (amount of O2 the water can hold). You can predict the solubility with the D.O. calculator at this site lutions/faq/predicting-DO.shtml

Water Quality Parameters Temperature - acts to regulate metabolism. Fish are cold blooded, meaning their metabolism is determined by external temperatures. Temperature - acts to regulate metabolism. Fish are cold blooded, meaning their metabolism is determined by external temperatures. Influences the holding capacity of gases in the water (including oxygen). The greater the temperature, the less oxygen can be carried in the water. Influences the holding capacity of gases in the water (including oxygen). The greater the temperature, the less oxygen can be carried in the water. Influences the form of nitrogen present in the water. Higher temperatures shifts nitrogen compounds to the more toxic unionized form..ammonia (NH3) Influences the form of nitrogen present in the water. Higher temperatures shifts nitrogen compounds to the more toxic unionized form..ammonia (NH3)

Nitrogen Cycle Nitrogen is present in 3 major forms in water. Nitrogen is present in 3 major forms in water. Ammonia is present primarily as a result of excretion of the fish. This is the most toxic form. Ammonia is present primarily as a result of excretion of the fish. This is the most toxic form. Ammonia shifts between the un-ionized form (NH3) and ionized form (ammonium - NH4-) Ammonia shifts between the un-ionized form (NH3) and ionized form (ammonium - NH4-) Important because NH3 is more toxic to fish and plants. Important because NH3 is more toxic to fish and plants. Time Tot/NH 3 -N (mg/L Temp  C pH UI/NH 3 -N (mg/L) 0400 hr 1600 hr 0400 hr 1600 hr

Nitrogen toxicity Ammonia is broken down in 2 steps by aerobic bacteria..the first step is to a less toxic form called nitrite (NO2). Still toxic and can cause brown blood disease Ammonia is broken down in 2 steps by aerobic bacteria..the first step is to a less toxic form called nitrite (NO2). Still toxic and can cause brown blood disease NO2 attaches to hemoglobin, preventing O2 from being carried by the hemoglobin. Blood turn brown and eventually fish can die. NO2 attaches to hemoglobin, preventing O2 from being carried by the hemoglobin. Blood turn brown and eventually fish can die. The process is carried out by a group of bacteria known as Nitrosomonas. They are aerobic…requiring oxygen to survive. The process is carried out by a group of bacteria known as Nitrosomonas. They are aerobic…requiring oxygen to survive.

Nitrogen Cycle Nitrite (NO2) is utilized by another group of bacteria…called Nitrobacter. These aerobic bacteria use nitrite and convert it to a form called nitrate (NO3). Nitrite (NO2) is utilized by another group of bacteria…called Nitrobacter. These aerobic bacteria use nitrite and convert it to a form called nitrate (NO3). Nitrate is relatively non- toxic. It is also the most preferred form of nitrogen for plants. Nitrate is relatively non- toxic. It is also the most preferred form of nitrogen for plants. Temperature and pH influence the survival and productivity of these bacteria (pH ) Temperature and pH influence the survival and productivity of these bacteria (pH )

pH pH is a measure of the acidity of the water. pH is a measure of the acidity of the water. It is given as a number from It is given as a number from A reading less than 7 is called acidic. A reading less than 7 is called acidic. A reading over 7 is alkaline or basic A reading over 7 is alkaline or basic A reading of 7 is neutral. A reading of 7 is neutral. Most food fish prefer water between 6.5 and 8.5 Most food fish prefer water between 6.5 and 8.5 Many ornamental fish prefer pH levels from Many ornamental fish prefer pH levels from

pH Why does pH shift? Why does pH shift? Natural processes like photosynthesis and respiration remove and add carbon from the system. During photosynthesis, carbon is removed. Adding carbonates (CO3) provides a supply of carbon to keep the pH from shifting drastically. Natural processes like photosynthesis and respiration remove and add carbon from the system. During photosynthesis, carbon is removed. Adding carbonates (CO3) provides a supply of carbon to keep the pH from shifting drastically. 6CO 2 + 6H 2 O + Energy  C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O + Energy  C 6 H 12 O 6 + 6O 2

pH A natural daily event is to see pH rise during daylight hours and drop during night. This fluctuation should be minimized for health of the fish A natural daily event is to see pH rise during daylight hours and drop during night. This fluctuation should be minimized for health of the fish

Hardness A measure of the amount of Calcium and Magnesium in water. It influences the pH by providing a buffer, so there are no sudden shifts in pH. It is measured in ppm CaCO3. The calcium is also used by fish and crustaceans for shell, scale, teeth and bone formation. The pH must be acidic to break the Ca-CO3 bond A measure of the amount of Calcium and Magnesium in water. It influences the pH by providing a buffer, so there are no sudden shifts in pH. It is measured in ppm CaCO3. The calcium is also used by fish and crustaceans for shell, scale, teeth and bone formation. The pH must be acidic to break the Ca-CO3 bond Free calcium in the water helps with osmoregulation Free calcium in the water helps with osmoregulation

Alkalinity Alkalinity is a measure of the amount of CO3 and HCO3- (carbonates and bicarbonates). These have a quicker reaction and stabilizing effect on pH. Gypsum and commercial lime are sources of carbonates. Alkalinity is a measure of the amount of CO3 and HCO3- (carbonates and bicarbonates). These have a quicker reaction and stabilizing effect on pH. Gypsum and commercial lime are sources of carbonates.

Alkalinity The most important components of alkalinity are carbonates and bicarbonates. The total alkalinity concentration should be no lower than 20 mg/L CaCO 3 in production ponds. Pond pH can swing widely during the day, measuring from 6 to 10, when alkalinity concentrations are below this level. Preferred range is mg/l The most important components of alkalinity are carbonates and bicarbonates. The total alkalinity concentration should be no lower than 20 mg/L CaCO 3 in production ponds. Pond pH can swing widely during the day, measuring from 6 to 10, when alkalinity concentrations are below this level. Preferred range is mg/l

Salinity A fish must maintain osmotic levels in its body A fish must maintain osmotic levels in its body They must keep water in or out of the body, depending on salinity of the environment. They must keep water in or out of the body, depending on salinity of the environment. They do this by Osmoregulation They do this by Osmoregulation Osmoregulation is controlling internal solutes Osmoregulation is controlling internal solutes Involves energetic cost of active transport Involves energetic cost of active transport In bony fishes this can be 5% of metabolic rate In bony fishes this can be 5% of metabolic rate

Solute regulation Transport solutes across the body surface Transport solutes across the body surface

Saving energy Salinity is increased in aquacultutre of freshwater fish to help reduce stress and can improve growth by reducing the energy needed for osmoregulation. Salinity is increased in aquacultutre of freshwater fish to help reduce stress and can improve growth by reducing the energy needed for osmoregulation. This savings in energy can be redirected towards other functions, such as growth or reproduction. This savings in energy can be redirected towards other functions, such as growth or reproduction.

Aeration The process of increasing dissolved oxygen to water. The process of increasing dissolved oxygen to water. Aerators designed for efficient O2 transfer. Aerators designed for efficient O2 transfer. Types of commercial aerators Types of commercial aerators Blowers Blowers Diaphragm pumps Diaphragm pumps Aspirating aerators Aspirating aerators Paddlewheels Paddlewheels

Types of aerators Blowers - high volume, low pressure. Long lasting, durable. Blowers - high volume, low pressure. Long lasting, durable. Cost - higher than diaphragm pump of same operating power, but with more air. Cost - higher than diaphragm pump of same operating power, but with more air.

Diaphragm pump Higher pressure, but lower volume than blower. Durable and can change diaphragm when necessary. Higher pressure, but lower volume than blower. Durable and can change diaphragm when necessary.

Aspirating aerator Most efficient aerator. Propeller spins rapidly, drawing air down the shaft. Most efficient aerator. Propeller spins rapidly, drawing air down the shaft. Blower assisted aspirator increases the volume of air injected into the water. Blower assisted aspirator increases the volume of air injected into the water.

Paddlewheels Agitate water and move water around pond. Efficient and durable. Electric or PTO driven Agitate water and move water around pond. Efficient and durable. Electric or PTO driven

Testing for D.O. Secchi Disc - most valuable when used to compare week-week or month-month. A reading of 12” -18” is best for aquaculture Secchi Disc - most valuable when used to compare week-week or month-month. A reading of 12” -18” is best for aquaculture

Waste Management Removal of solid waste is crucial. Removal of solid waste is crucial. Prevents less ammonia from being released. Prevents less ammonia from being released. Improves clarity for light penetration..good for algae production. Improves clarity for light penetration..good for algae production. Keep fish in good health. Keep fish in good health.

Environmental factors Attention to the affect of aquaculture to the environment can reduce problems, improve profitability, and maintain social responsibility. Attention to the affect of aquaculture to the environment can reduce problems, improve profitability, and maintain social responsibility. Aquaculture can be bad for the environment if not planned properly. Aquaculture can be bad for the environment if not planned properly. Recycling opportunities are available in all aspects of aquaculture. Recycling opportunities are available in all aspects of aquaculture.

Growth Factors  Feed – nutrients, digestibility, cost, availability  Temperature  Dissolved oxygen and stress  Water quality  Crowding  Males vs females  Disease

Integration with plants & Animals Use of freshwater effluent to irrigate plants is a god way to recycle waste products. Use of freshwater effluent to irrigate plants is a god way to recycle waste products. Irrigation to garden plot Irrigation to garden plot Aquaponics (Aquaculture / Hydroponics) system Aquaponics (Aquaculture / Hydroponics) system

2 Crops per Drop Each drop of water used can go towards growing fish and a plant crop in standard garden plot Each drop of water used can go towards growing fish and a plant crop in standard garden plot

Aquaponics Fish and plants share the same water in the system as it recirculates through each component. Fish and plants share the same water in the system as it recirculates through each component.