Ponds, ponds, ponds...Lecture 5Dr. Craig S. KasperFAS 1012C: Introduction to Aquaculture

AcknowledgementAppreciation and sincere thanks are given to Dr. Joe Fox (TAMUCC) who kindly donated material for this presentation!!

Please visit his website!(http://www.sci.tamucc.edu/pals/maric/Index/WEBPAGE/mari1.htm)

IntroductionPonds were used as one of the first forms of aquaculture.Dates back to ancient China.Already had the water...just add fish, feed, and presto!Pond production has come along way since then!

POND DESIGN CRITERIA (Ideal)Screened inflow gates at shallow end of pondScreened harvest gates at deep endSlope to harvest basin (0.5-1.0%)Water depth 1.25 2.00 MFeeding tray piersRounded or square corners, steps or ramps for entryPrimary dikes (levees) wide enough to accommodate vehicles

GENERAL DESIGN, INTENSIVE POND

Pond LeveeworkCONSTRUCTION CRITERIALevees are typically constructed by D6- (Catepillar) sized bulldozers

Construction is first undertaken on ponds nearest the sedimentation basins and pump station

Bulldozers push earth up to create general form of the levee walls

Follow stakes set along the length of the pond

Smaller dozers used to put on finishing touches

Pond LeveeworkDESIGN CRITERIAHeights determined by pond bottom elevation, tidal amplitude

Perimeter levee often required for protection in flood areas

Levees trapezoidal with slopes 1:2 for high clay, 1:3-4 low clay

Levee crown width varies with use

Width of crown: 5 m (driving), 3m (walking)

Crown is sloped to reduce puddles on levee top

Once formed, levees are sprigged with grass to reduce erosion

Pond LeveeworkCONSTRUCTION CRITERIAErosion is the main problem in maintaining levee slopes

Source: both rainfall and wave action

Solution: plants and vegetation (local grasses or Salicornia sp.) as soon as possible

Pond sides receiving wind could be reinforced with rocks (contracted service)

Tops of levees definitely need layer of rocks, especially if high clay content

Typical Cross-section of Pond LeveeWIDTH=4 TO 5 MPOND SIDE4.0CANAL SIDE2.0M1.5MCUT-OFF TRENCH2.0M3.0

Preventing LeaksMinimize amount of loss due to seepage - Proper compaction - Core trenching - Vertical plastic membranes - Vegetative coverageRemove burrowing animals (turtles, muskrat) (.243 Winchester works great!)Optimal clay contentConstruction during dry season

Pond BottomCONSTRUCTION CRITERIAIf detailed pond bottom slopes are required, usually accomplished by scrapersSmall 4-6 m3 earthmovers towed by 4X4 tractors, laser-guided Bottom slope from upper end to lower end of pond usually 1m:250-500m or 0.4-0.2% for large pondsIn simple ponds, follows natural slope to estuaryMust insure at least 20 cm height of harvest gate above high tide elevation (varies considerably by site)

POND BOTTOM DESIGNScrowncanalcanalcanalcanalplateauplateau

POND BOTTOM ELEVATIONPrimary design criterionBased upon tidal amplitude (or drainage)Above the freshwater tableAbove mean high tideDetermines canal/levee heightPond should be drainable at all times

Pond Bottom vs. TideWHERE SHOULD YOU BE????

WATER CONTROL STRUCTURESINFLOW GATESUsed for control of pond water exchangeConcrete structures with screen/bag filters on both sides of LeveeDual primary screens for pre-filtration (1/4" to 1/2)Secondary filtration screen bag eliminates potentialpredators (250-500 M)Flashboards for controlling flow rate of water entering pondMultiple gates in larger ponds

CONCRETE APRONPRIMARY FILTERLevee CROWNLevee SLOPELevee SLOPEFLASH BOARDSWING WALLBAG FILTERCORRUGATED PLASTIC TUBESPLAN VIEW OF TYPICAL INFLOW GATE

TOP OF LeveeCANAL SIDEPOND SIDEBAG FILTERATTACHMENT SLOTFLASHBOARDSFILTER SLOTPRIMARY FILTERCULVERT PIPECROSS SECTION OF TYPICAL INFLOW GATE

WATER CONTROL STRUCTURESHARVEST GATEConcrete w/harvest basin in pondNumber/size of gates depends on speed of harvest requiredScreen to retain shrimp, mesh according to size Use of flashboardsCanal side often modified for harvest pump

Levee CROWNLevee SLOPELevee SLOPEHARVEST BASINWING WALLFILTER SCREENFLASH BOARDCULVERT TUBESPUMP BOXNET SLOTDRAINAGE CANALPLAN VIEW OF HARVEST GATE

Harvest Gate: inflow

Harvest Gate: outflow

Harvest Gates: outflow

Harvest Gates: multiple

Gate Construction

POND AERATION/OXYGENATIONlevel determined by oxygen demandpumping vs. artificial aerationused for oxygenation and solids mobilizationefficiency of devices variespaddlewheels: 2.13 kg O2/kwhpropeller/aspirator: 1.58diffusors: 0.97

Typical Aeratorsair injectorpaddlewheel

Multiple Aeration Units

Estimating Oxygen RequirementDuring paddlewheel aeration and high density culture O2 requirement usually estimated on the basis of feed application to pond

1 kg of feed = 0.2 kg O2 consumed via respiration300 kg feed = 60 kg O2 consumed/day

Caveat: Some O2 consumed by shrimp/fish, but more by primary productivity

Estimating Paddlewheel Requirements

Additional Paddlewheel GuidelinesUse high quality switch boxes and adequate guage wire

Orient paddlewheels to reduce dead spots in ponds (locate in corners); dont change orientation during a run

More paddlewheels (e.g., 1.0 hp units) = fewer dead spots but more $$$ (units & parts)

Stainless steel = less corrosion!

Pay attention to electrical demand and quality of electricity (less motor repair)

ELECTRICAL SUPPLYMore tecnology = more demand!

Semi-intensive ponds need electricity for ice production, living accomodations, perimeter lighting, laboratory, fry acclimation facility

Usually provided by diesel generators (more dependable and, therefore, cheaper in the long run)

Intensive and super-intensive operations have large energy demand (aeration is about 90% of demand)

Electrical DistributionDistribution via high tension line with 20-50 kVA step-down transformers situated throughout the farm

Demand could be as high as 50 kVA per ha

300 ha intensive farm could have 3,000 one hp paddlewheels = 2.5 megawatt demand

Electrical distribution system could cost well over $1 million

ARTIFICIAL SUBSTRATES(POND LINERS)Used in areas where soil quality is poor (percolation/toxicity)Also used to reduce effluent solids via erosion of pond bottom and drainage canalCost now $0.25/m2Long-term viability and uv resistanceUse at least 30 mil thicknessDont install yourself!!(unless very good at it!)

Soil-Cement LinersMade from 1:6-8 mixture of cement and sandPond raked down to 3Cement added to achieve ratioWatered and smoothed via 3,000 lb roller compactorRate: 1ha/wk

Stocking DensitiesSpecies dependent:-catfish (3500-5000 fish/acre w/aeration)-tilapia... similar-prawn-start with 16,000/acre if substraight present-flounder-not density, but bottom coverage, usually tolerate 200% bottom coverage if adequate water flow.