Oyster Farming Fundamentals, Class Four, Mississippi

Transcript

1. Oyster Farming Fundamentals OFF/Class of 2018 Mississippi Department of Marine Resources, Auburn University, Alabama Cooperative Extension
2. Class Topics — Class One — Introductions — What is off-bottom oyster farming and why do it? — Oyster Biology and Life Cycle — Understanding Triploidy — Introduction to Business Planning — Field Visit to Hatchery in Pass Christian — Class Two – Starting an Oyster Farm — Site Selection — Gear Options — Introduction to Gear Assembly — Permitting — Field Visit to Oyster Farm
   
   
3. Class Topics — Class Three – Operating an Oyster Farm — Grading & Splitting — Controlling Bio-Fouling — Nursery Options — Class Four – Operating an Oyster Farm — Business Plan – Rusty Grice — Inventory Management — Protecting Public Health — Storm Preparation — Mitigating Hazards — Harvest Requirements – Jason Rider
   
4. Class Topics — Class Five – Making the Most of an Oyster Farm — Best Management Practices — Marketing and Branding — Basics of Distribution — Risk Management — Business Planning – Conclusion — Seed Counting and Taking Delivery
5. Nursery Options for Seed
6. Nursery Stage — Can get seed as small as retained on 0.75 mm mesh — Can raise them at fairly high densities — Very vulnerable to predators or loss due to sloppy handling — For sake of discussion, nursery stage ends when seed are retained on 12 mm mesh (R12) and begin grow-out — (‘pepper flakes’ to ‘quarters’)
7. Nursery Options for Oyster Seed — Upwellers — Very high densities of seed — Rely on forced high flow of seawater usually by a pump — Can get seed as small as 1 mm (retained on 0.75 m) — Field containers/bags/baske ts — Lower densities — Rely on passive flow of seawater — Can get seed as small as R2 OR purchase larger seed from a nursery operation
8. Upwellers — Either above the water line (usually land- based) or in the water (floating upwellers) — Floating are often called FLUPSYs
9. Production in Upwellers — With grading throughout season, can produce ~1 million seed retained on 12 mm mesh (R12) — Cleaning seed and silos regularly — Runs on axial flow pump so relatively low electric costs — High flow is key — Ideally 100 gpm per silo — Purchased turn key $9,000
10. Upwellers above the water line — Upweller silos can be built relatively inexpensively — Still require regular maintenance of seed and silos
11. Upwellers above the water line — Upwellers can also be put indoors/shelter — Can be built out of fiberglass — Note that silo shape varies Photo by @gilliangrice
12. Bottle Nurseries Photo and video by @gilliangrice
13. Upweller tending — All upwellers have water (and food and oxygen) come up and go past the seed — Require frequent tending since seed are at such high density — Personally, I washed my silos & seed at least every other day Photo by @gilliangrice
14. — Construction of ‘Supan Power Silos’ - https://www.youtube.com/watch?v=wcd6m6c51Gg — Paddlewheel floating upweller - https://www.youtube.com/watch?v=z5oDgQG2I74 Upweller Videos
15. Field nursery — Can opt to raise seed in the field in fine mesh bags — Caveats! — Small seed are easy to lose out of even small holes — Fouling is much faster on fine mesh
16. For field nursery, routinely grading and moving to new mesh — For a May 1 spawn, we typically have seed that retain on 2 mm mesh by June 15th or so (6 wks) — These go into a 1.5 mm mesh ‘sleeve’ @ 10,000 seed/sleeve using a floating flippable cage (e.g., OysterGro) — Works with any container system though (e.g., ALS)
17. Those seed get deployed at your field site
18. Two weeks later … — After about two weeks (July 1), the seed will mostly retain on a 4.5 mm mesh and go in a 2 ml bag @ 5,000 seed/bag
19. Two more weeks later … — After about two weeks (July 15), the seed will mostly retain on a 6 mm mesh and go in a 4.5 ml bag @ 2,500 seed/bag — Up to this point, zero maintenance between gradings and re- baggings
20. Splitting and Desiccation — After about 2 more weeks (August 1), seed will have gotten larger, and can split the densities in half, so there are only 1,250 seed/bag — At this point, we begin weekly desiccation of the seed
21. To grow-out — By August 15-30, seed will retain on a 12 mm mesh, so these are put into 9.5 ml bags which can be used through grow-out if properly maintained — Have decision if want to get the R12 seed at final grow- out density (150/bag) or keep them at higher densities (no more than 1,250 and can’t be kept there long)
22. — June 15th – Need 10 1.5 ml bags, and 3 OysterGro minis — July 1 – Need 20 2 ml bags and 2 more OysterGro minis (5 total) — July 15 – Need 40 4.5 ml bags and 5 more OysterGro minis (10 total) — Aug. 1 – Need 40 more 4.5 ml bags (80 total) and 10 more OysterGro minis (20 total) — [~$500-$600 worth of bags, or $5,000-$6,000 of bags for 1 million seed] For every 100,000 oyster seed
23. — By Aug. 15th – If going to final grow-out density (and assuming 96% survival/retention), need 640 9.5 ml bags and 160 OysterGro minis to get these seed to 150/bag (or 600/cage) — (As an aside, with our current permitting in Alabama, that is about 1 acre of cages.) For every 100,000 oyster seed
24. Additional considerations for field nursery — Total time tending seed is approximately 2-2.5 months — Minimal maintenance between gradings — Does require power washing bags after use
25. Comparing growth and survival — Highly variable — Personally, I have seen sites where field nurseries outperform upwellers and other sites where upwellers outperform field nurseries — Differences in handling? — Differences in food in water? — In my opinion, either method can give you very high growth and survival
26. Which option is for you? — Upwellers + Convenient + Can control flow even in low flow environment − Power bill − Need to get upweller moved for storms − Can be expensive to build — Field nursery + No power bill + Keeping an eye on your site + Only periodic maintenance − Multiple bag sizes needed
27. Inventory — How many oysters do you have? — What size are they? — Where are they? — How do different batches perform? — What is the value of my crop right now?
28. Traditional Methods Figure 1. Whiteboard as oyster farm management tool at Hog Island Oyster Company
29. Traditional Methods — Whiteboard — Notebook — Excel (with some modern twists) — Color-coded tags — Memory
30. New Options? — Apps/software — RFID? — GIS packages
31. Inventory Management — Better informed decisions about crop management — Improved production — Higher efficiency — More accurate valuation — Better prediction to market
32. Public Health — Inherent risks with consumption of raw shellfish — Pollution associated with human sewage — Heavy metals and other contaminants — Toxins from harmful algal blooms — Oil spills, chemicals — Vibrios
33. Vibrio and Oysters — Pathogenic bacteria naturally found in marine waters — Two species of Vibrio: — Vibrio parahaemolyticus (Vp) — Vibrio vulnificus (Vv) — Increase in warmer temperatures — Routine handling of oysters on farm can increase levels of Vibrio — Interrupts filter feeding — Exposure to warm air temperatures — Critical to control time at elevated temperatures after harvest
34. Raw Oyster Consumption and Vibrio Risks — 93% of Vibrio infections occur from consuming raw shellfish (Oliver 2013) — Infections can cause: — Rapid septicemia — Acute gasteroenteritis — Death (especially in immune compromised individuals) — Need to consider any increased risk of infection (maintain customer satisfaction!)
35. Vibrio Risk Management — Exposure to warmer temperatures à increased Vibrio levels — To minimize this, must consider the “time- temperature” window — Oysters must be refrigerated within a specified amount of time after harvest — Ex: Summertime harvest in Alabama allows for 1 hour — Why? — Eliminate increased risk of Vibrio infection — Allow oysters to be sold in the raw market
36. Vibrio vulnificus levels in Gulf Oysters 0.1 1 10 100 1000 10000 Log (10) V. vulnificus/g J F M A M J J A S O N D Month Slide from A. DePaola: Motes et al. 1998
37. Effect of Temperature on Vv densities in Gulf Coast oysters 0.01 0.1 1 10 100 1000 10000 100000 1000000 40 50 60 70 80 90 water temperature (F) Vv density in oysters (MPN/g) Motes (averaged replicates) regression fit (MLE) Slide from A. DePaola: Motes et al. 1998
38. How Can a Grower Affect the Risk Before Harvest? — Culture practices that expose oysters to air: — Desiccation — Tumbling — Grading/sorting — Transport from farm to refrigeration — Many states now require specified periods of re- submersion
39. How Can a Grower Affect the Risk After Harvest? — Get the oysters cold as soon as possible — Treat time/temperature windows as the maximum but strive for shorter — Think about the oysters prior to harvest; are they open and filtering right up to harvest? — Keep them cold!
40. In the Cone — Have sense of timeline — Look at multiple forecasts — Evaluate exposure — Take precautionary measures — Tidy up farm — Check lines — Make sure not overstocked — Be ready to implement plan
41. Storm is Coming — Implement plan — Sink cages or lower baskets — Secure land-based operations — Secure boat/vessels
42. After the Storm — Get oysters back off the bottom as soon as feasible — Have supplies on hand to repair — Communicate with customers — Marketing
43. Have a Plan! — Seriously, have a written plan — Consider a tiered approach — Keep inventory of crop, cages, machinery — Keep farm photos or videos — Practice a plan — Remember that it won’t be calm seas when implementing — Time yourself. How much time will it take you to secure all your gear? — Secure your gear in such a way that the oysters can stay alive for 2-3 weeks if the gear remains in that position. — Know what is realistic in a given time — Keep farm managed well prior to a storm