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Questions and Answers
Raceways consist of rectangular basins or canals constructed of ______.
concrete
A continuous water flow-through in raceways provides the required level of water ______.
quality
Raceways are usually used for some marine species that need a constant water flow, such as juvenile ______.
salmon
Water flow through raceways typically provides three or more exchanges per ______.
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Solid wastes that accumulate at the raceway bottom can be removed by ______.
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Oxygen levels in the water can be kept high if the raceway units are placed one after the other with intermediate drops over ______.
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Raceway ponds are used in the cultivation of ______.
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The smallest raceway ponds have been used for the production of fish ______.
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Earthen raceways are cost-effective but cleaning them is difficult because their ______ linings are fragile.
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The inlets in reinforced concrete raceways circulate the water in the system, allowing solid wastes to be removed through the outlet located in the ______ of the silo.
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Study Notes
Raceways
- A flow-through aquaculture system
- Usually rectangular basins or canals made of concrete
- Allows for higher densities of fish (10-15 fish per cubic foot)
- Used for marine species like juvenile salmon, sea bass, and seabream
- Dimensions of 50-100 ft long, 10-30 ft wide, and 3-6 ft deep
- Require 3 or more water exchanges per hour
- Water velocity must be at least 0.1 ft/sec
Water Sources
- Streams
- Springs
- Reservoirs
- Deep wells
Monitoring Water Quality
- Water flow rate
- pH levels
- Temperature
- Dissolved oxygen levels
- Suspended and solid waste material
Water Flow
- Must be high enough to meet the respiratory needs of the fish
- Replaces existing water with new water
- Solid wastes removed using pumps
- Oxygen levels maintained by placing raceways sequentially with drops over weirs
- Water should be replaced roughly every hour
- Flow rate can change throughout the year
Types of Raceways
- Raceway ponds: shallow ponds used to cultivate algae, divided into a rectangular grid, with each rectangle containing an oval-shaped channel and a paddle wheel to circulate water
- Earthen raceways with plastic liners: inexpensive and easy to build, but difficult to clean and disinfect
- Reinforced concrete/concrete silo: water is circulated using inlets, solid waste is removed using an outlet in the center of the silo
- Raceway tanks: can be built from polyester resin, have smooth walls, mobile and easy to service, limited to a small size (5 cubic meters)
Technologies for Removal of Solid Waste
- Microscreens
- Dual-drain tanks
- Swirl separators
- Plate separators
- Baffles
- Media filters
- Air flotation
- Foam fractionation
- Chemical flocculation
- Constructed wetlands
- Sedimentation (settling)
System of Operation
- Aeration: dissolved oxygen can be increased using aerating machines, including pumps, agitators, compressors, and blowers
- Removal of solid waste: accumulated waste spoils water quality, can be removed by pumping or increasing water flow, lowering water level to 30 cm deep makes removal more effective
- Productivity: productivity is linked to water exchange rate, improved productivity allows businesses to meet obligations and improve market competitiveness
- Wastewater Treatment: critical component of raceway operation, improper treatment can lead to red tide outbreaks
Advantages of Raceways
- Higher stocking densities
- Improved water quality
- Reduced manpower needs
- Ease of feeding
- Ease of grading
- Ease of harvest
- Reduced off-flavor
- Easier disease detection
- Easier disease treatment
- Closer monitoring of growth and mortality
- Easier management inputs like size grading
Disadvantages of Raceways
- Finding and securing a proper water supply is crucial
- Large constant flows of high-quality water are needed
- Commercial viability often requires gravity flow between raceways
- Suitable topography and elevation of water source are required
- Higher densities can lead to faster disease spread and less reaction time
- Culture density is dependent on water flow
- Water sources are often colder than lakes/rivers
- Frequent cleaning is required
- Poaching is a concern
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Description
This quiz provides insights into raceway systems in aquaculture, focusing on their construction, water sources, and monitoring water quality. Learn about the critical factors affecting fish health and growth in these systems. Perfect for students and professionals in aquaculture and environmental science.
