Ponds, ponds, ponds...

1. Ponds, ponds, ponds... Lecture 5 Dr. Craig S. Kasper FAS 1012C: Introduction to Aquaculture

2. Acknowledgement • Appreciation 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)

3. Introduction • Ponds 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!

4. POND DESIGN CRITERIA (Ideal) • Screened inflow gates at shallow end of pond • Screened harvest gates at deep end • Slope to harvest basin (0.5-1.0%) • Water depth 1.25  2.00 M • Feeding tray piers • Rounded or square corners, steps or ramps for entry • Primary dikes (levees) wide enough to accommodate vehicles

5. Levee Levee SLOPE 1 Levee Levee INFLOWGATE HARVESTBOX FILTERBAG HARVESTBASIN SLOPE 3 HARVESTGATE PRIMARYFILTER SLOPE 2 Levee Levee Levee Levee RECIRC CANAL DISTRIBUTION CANAL PADDLEWHEEL AERATOR GENERAL DESIGN, INTENSIVE POND

6. Pond LeveeworkCONSTRUCTION CRITERIA • Levees 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

7. Pond LeveeworkDESIGN CRITERIA • Heights 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

8. Pond LeveeworkCONSTRUCTION CRITERIA • Erosion 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

9. Typical Cross-section of Pond Levee WIDTH=4 TO 5 M CANALSIDE PONDSIDE 2.0M 2.0M 1.5M 4.0 3.0 CUT-OFFTRENCH

10. Preventing Leaks • Minimize amount of loss due to seepage- Proper compaction- Core trenching- Vertical plastic membranes- Vegetative coverage • Remove burrowing animals (turtles, muskrat) (.243 Winchester works great!) • Optimal clay content • Construction during dry season

11. Pond BottomCONSTRUCTION CRITERIA • If detailed pond bottom slopes are required, usually accomplished by scrapers • Small 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 ponds • In simple ponds, follows natural slope to estuary • Must insure at least 20 cm height of harvest gate above high tide elevation (varies considerably by site)

12. POND BOTTOM DESIGNS canal crown canal canal plateau canal plateau

13. POND BOTTOM ELEVATION • Primary design criterion • Based upon tidal amplitude (or drainage) • Above the freshwater table • Above mean high tide • Determines canal/levee height • Pond should be drainable at all times

14. Pond Bottom vs. Tide WHERE SHOULD YOU BE????

15. WATER CONTROL STRUCTURESINFLOW GATES • Used for control of pond water exchange • Concrete structures with screen/bag filters on both sides of Levee • Dual primary screens for pre-filtration (1/4" to 1/2“) • Secondary filtration screen bag eliminates potential predators (250-500 µM) • Flashboards for controlling flow rate of water entering pond • Multiple gates in larger ponds

16. LeveeCROWN LeveeSLOPE LeveeSLOPE CONCRETEAPRON CORRUGATEDPLASTICTUBES WINGWALL FLASHBOARDS BAGFILTER PRIMARYFILTER PLAN VIEW OF TYPICAL INFLOW GATE

17. CROSS SECTION OF TYPICAL INFLOW GATE CANALSIDE ATTACHMENTSLOT TOP OF Levee PONDSIDE CULVERTPIPE BAGFILTER PRIMARYFILTER FLASHBOARDS FILTER SLOT

20. WATER CONTROL STRUCTURESHARVEST GATE • Concrete w/harvest basin in pond • Number/size of gates depends on speed of harvest required • Screen to retain shrimp, mesh according to size • Use of flashboards • Canal side often modified for harvest pump

21. LeveeSLOPE LeveeCROWN LeveeSLOPE DRAINAGECANAL HARVESTBASIN PUMP BOX CULVERT TUBES NET SLOT FILTERSCREEN FLASHBOARD WINGWALL PLAN VIEW OF HARVEST GATE

25. Harvest Gate:inflow

26. Harvest Gate:outflow

27. Harvest Gates:outflow

28. Harvest Gates:multiple

29. Gate Construction

30. POND AERATION/OXYGENATION • level determined by oxygen demand • pumping vs. artificial aeration • used for oxygenation and solids mobilization • efficiency of devices varies • paddlewheels: 2.13 kg O2/kwh • propeller/aspirator: 1.58 • diffusors: 0.97

31. Typical Aerators paddlewheel air injector

32. Multiple Aeration Units

33. Estimating Oxygen Requirement • During 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 respiration • 300 kg feed = 60 kg O2 consumed/day • Caveat: Some O2 consumed by shrimp/fish, but more by primary productivity

34. Estimating Paddlewheel Requirements

35. Additional Paddlewheel Guidelines • Use high quality switch boxes and adequate guage wire • Orient paddlewheels to reduce “dead” spots in ponds (locate in corners); don’t 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)

36. ELECTRICAL SUPPLY • More 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)

37. Electrical Distribution • Distribution 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

38. 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 canal • Cost now $0.25/m2 • Long-term viability and uv resistance • Use at least 30 mil thickness • Don’t install yourself!! (unless very good at it!)

39. Soil-Cement Liners • Made from 1:6-8 mixture of cement and sand • Pond raked down to 3” • Cement added to achieve ratio • Watered and smoothed via 3,000 lb roller compactor • Rate: 1ha/wk

40. Stocking Densities • Species 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.