Oyster Culture. Vanessa Weldon extension

Transcription

1 Oyster Culture Vanessa Weldon extension

2 Overview Biology Lifecycle Hatchery Nursery Grow-out methods Extensive Intensive Advances in culture techniques Issues facing the oyster industry

3 Basic oyster biology Diploid (right) and Triploid (left) Louisiana Crassostrea virgnica

4 Oyster Life Cycle

5 Hatchery Phase Hatcheries are common on the west and northeast coasts Gulf of Mexico there are no commercial hatcheries Hatcheries face many of the same issue that animals in the wild

6 Hatchery Phase - Algae Batch Culture Open air, easily contaminated, labor intensive, one tank may last few days Continuous culture Flow-through, high density production, higher cost, labor intensive in beginning, one bag can last over a month

7 Alga Growth Curve

8 Hatchery Phase - Broodstock Harvest from wild Conditioning Temperature control Water quality Quality diet

9 Hatchery Phase Induced Spawn Ripe broodstock Recircualting spawning tank Fluctuate temperature Typically using ice Can take hours Sacraficing a male can help females spawn Higher quality eggs and sperm Photo courtesy of Horn Point Oyster Hatchery, University of Maryland

10 Hatchery Phase Strip Spawn Shuck Sample gonads Sex determination Egg or sperm quality Scrape gonad into a container Add seawater to hydrate eggs Do not add water to males (starts sperm moving) Screen out debris Collect eggs or sperm, mix

11 Induced vs. Strip Spawn Induced can give better quality eggs Broodstock sacrificed in strip spawn Induced can take much longer Strip spawn allows for control of time of fertilization Ideal for polyploidy culture

12 Hatchery Phase - Larviculture Takes 10 to 20 days until metamophosis Temperature Water quality (toxins or bacteria will lower survival) Food Quality Proper handling

13 Hatchery Phase - Larviculture Days after spawn Table 1. Larviculture parameters (Wallace et al. 2008) Sieve size μm Larval density Larval height (μm) (diagonal) (larvae/ml) Algae density (cells/ml) , (50) , (75) , (75) , (103) 4 50, (103) 4 50, (141) , (166) ,000

14 Hatchery Phase - Setting Pediveliger or eyed larvea final stage Only time in life cycle where the oyster uses its foot Once the oyster sets it s will not move under it s own power A photomicrograph of an eyed oyster larvae. Photo by Michael Congrove, Virginia Institute of Marine Science, The College of William and Mary

15 Setting - Cultch Material oysters set on Chicken scratch Crushed coral Oyster shells Size of Cultch critical Smaller Cultch = individual oyster Oyster with spat Photograph courtesy of Hama Hama Oysters

16 Nursery phase High intensity = high density Flow-through Upwelling keeps oyster in suspension Natural food supply Exposed to weather Solar powered Floating Upweller System (aka FLUPSY). Photo courtesy of Dale Leavitt, Center for Economic and Environmental Development, Roger Williams University

17 Extensive Culture On-bottom leased culture Typically do not obtain seed from hatcheries Obtain seed for managed leases or from public grounds

18 barge sprays off oysters shells to build a reef in Dicks Bay (Photo courtesy of Ken Blevins, Wilmington Star-News).

19 Grow out Extensive

20 Extensive Culture Pros Less investment No hatchery required Several leases throughout the region can reduce impact of major events Cons No control over survival Labor intensive Fouling and disease can be issues Slower growth

21 Intensive Culture: Grow-out Higher density Typically off-bottom Predator exclusion cages, rafts, bags Generally higher survival and faster growth rate

22 Intensive Culture: Grow-out

23 Intensive Culture: Grow-out Tidal bag culture, tidal influx rolls bags giving and ideal shape and exposure to air reduces fouling organisms Photograph courtesy of Hama Hama Oysters

24 Intensive Culture: Grow-out

25 Fouling Control Off-bottom culture not treated for fouling (simulated on-bottom culture) Off-bottom culture exposed at low-tide

26 Intensive Culture: Grow-out Pros Can measure growth and survival rates Stock systems to allow harvest throughout the year Protects the investment of hatchery reared oysters Cons Capital investment Handling fouling issues Environmental impact issues Natural disasters Requires several permits

27 Advances in Oyster Culture Selection and breeding for disease resistance Increased meat yield through polyploidy culture Post-harvest treatment for safer consumption Predator reduction

28 Issue facing Oyster culture industry Increase in Vibrios Harmful to humans Harmful to oysters Ocean Acidification Decreased larval survival Effects on spawning or fertilization rates? Diseases MSX Emerging disease