flow-through culture
TRANSCRIPT
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Flow-through Culture(Raceways)
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Production Intensity
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Flow-through Culture
Advantages Disadvantages
Continual flow replaces: Oxygen Temperature
While removing: Nitrogen wastes CO2
Can support higher production levels; up to 1,000x greater than pond.
Lower concentrations of solids & nutrients in effluents.
Easier harvesting, feeding, & grading.
Large volumes of water needed.
Difficulties in cleaning.
Difficulties in removing effluents from:
High volume discharge.
Low concentration discharge.
Fish consume more food
Energy for swimming
DO must be maintained at high level.
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Construction
Traditional: earthen
More recently: concrete, plastic, metal.
Indoors: temperature may be controlled.
Short-term: depuration & holdover.
Based on
Constant, large volume of H2O
100-1,000 gpm
Topography
Discharge
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Site Selection
Water supply
Use large quantities of water (raceways have continual water exchange, often 2 to 10 exchanges/hr).
Gravity springs are most economical
Location
Near water supply
Topography
8-10 percent slope
18-24 inch water drop
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Water Treatment
Prescreening
Aeration & removal of unwanted gases
UV sterilization
Filtration & removal of invasives
Head-water pond (settling of suspended solids)
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Water Discharge
Raceways should flow into settling pond or wetland.
Regulates temperature, nitrogen, DO, escapees, but must also be managed.
Discharge is regulated for:
Solids (excess feed, waste & carcasses)
Eutrophication (N & P)
Temperature
Pesticides
Pharmaceuticals
Escapes
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Solids Capture Systems
• Quiescent zone
• Full-flow settling basin
• Off-line settling basin
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Types of Raceways
Single pass
Parallel – flow through one raceway (channel)
Series – flows through multiple raceways (most common)
Recirculating
Floating
Series
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Single Pass Raceway
Length: width: height ratio
30:3:1 for adults
6:1:1 for fingerlings
3:1:1 for fry
Water depth not to exceed 3-4 ft.
Units are arranged as tiers with 1-2’ drop, which replaces ~50% of O2 from previous section.
Fish are sorted (youngest to oldest)
Water flows via gravity.
Baffles, quiescent zone, levees, splash boards & screening.
Self-cleaning
For Example: 120 ft x 12 ft x 4 ft
120 ft
12 ft
4 ft
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Splash boards
Levee with screening
Quiescent zone
Baffles
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Feeding
Multiple demand feeders or automated feeders.
Feed often (8-10 times/day) so waste does not accumulate.
Offer feed over a large area (crowded fish deplete O2; feeding fish deplete O2).
Neutral or sinking feed is best.
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Aeration
Oxygen not usually a problem unless using recirculated system. Flow influences aeration:
Laminar flow (fast center, slower edges) Turbulent (lightly mixed) flow
As water flows: DO decreases Ammonia & carbon dioxide increase
Packed column Tubes “packed” with screen where water flows over screening; or
oxygen can be injected. Can be used to reduce nitrogen levels.
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Harvest
Grading must be done (grading bars).
Individual growth differs
Hierarchies
Seines and/or nets (crowding to capture)
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Floating Raceway System
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Floating Raceway Schematic
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Single channel view - direction of flow
Air lift intake pipes
Outflow screens
Construction of liner
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Feeder locations Avian predator modifications
Year-round operation
High-density culturing
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Water ExchangeAdjustable water velocity (m/s)
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Growth of Yellow Perch Over Two Years at Cranberry Farm
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Weekly Mortality and Water Temperature
Date (2003)
Jul Jul Aug Aug Sep Sep Oct Oct
Te
mpe
ratu
re °
F
50
55
60
65
70
75
80P
erc
ent W
eekly
Mo
rtality
0
1
2
3
4
5Temperature
Mortality Raceway #1
Mortality Raceway #2
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Startup Investment
Capital investment
3-channel raceway $12,000 ($4,000 per raceway)
Barrels & docks $1,500 ($500 per raceway)
Operating expenses
Fish feed $1,250 / 80,000 perch for 6 months
Electricity $800 / year
Labor $7,000 / year
Yellow perch fingerlings $12,350 / 80,000 perch
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Paddlewheel
Settling chamber
Algae biofilter
Filt
er-f
eed
er
cham
be
r
Cu
ltu
re s
pec
ies
cham
be
r
Partitioned Aquaculture System (PAS)
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Partitioned Aquaculture System
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Factors in PAS
• Waste treatment reservoir must be shallow (30-60 cm)
• Need green algae in constant growth phase
• Solid waste removal
• Predator exclusion
• Winter / freezing
• Ratio of pond sizes:
– Fish production 5% of water treatment
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Split-Pond Culture