Veterans Day holiday Thursday, Nov. 11 No discussion Thursday Nov. 11 or Friday Nov. 12 Read for the fun of it Clamelot 1
Molluscan Aquaculture 13,093,000 mt = ~ 19% of total aquaculture = ~ 25% of animal aquacult. = ~ 12% of the value of animal aquaculture Clams (carpet shells) = 7,260,000 mt = 4,164,000 mt (10% animal aquaculture) Japanese oyster* = 4,034,000 mt (97%) Other mollusks = 1,690,000 mt including (22,000 mt pearl oysters) & (247,000 mt freshwater mollusks) 2
OYSTER AQUACULTURE 3
Aquaculture systems - classification Extensive few animals/area Intensive many Extractive nature food source Input-dependent man 4
Of all the oysters produced 4,400,000 mt or 97 % are a single species the Japanese oyster (Crassotrea gigas) Why is this? 5
CALIFORNIA OYSTER INDUSTRY 6
THE WORLD RUSHES IN Middle of 1848 ~ 14,000 7500 Californians 6500 Americans End of 1849 ~100,000 7
AVERAGE MINER WAGE $ 10 20/DAY Standard Fare Flour/lb... 25 to 30 cents Dried meat Beef/lb... 40 to 75 cents Salt Pork/lb... 40 to 75 cents Beans/lb... 20 cents Coffee/lb... 20 to 33 cents Sugar/lb... 30 to 50 cents Hangtown fries (oysters, bacon & eggs)...$ 6.00 8
Olympia oyster = Ostrea conchaphila (formerly O. lurida) S.F. oyster beds depleted by 1851 Fresh East Coast oysters arriving by ship in barrels cost $6 apiece 9
1850 1869 Olympia oysters from Shoalwater Bay (Willapa Bay) & Puget Sound, WA 1851 = 5,000 bushels 1860 = 30,000 bushels 1890 = 130,000 bushels 1920 = stocks depleted 10
1875 Transcontinental Railroad Relaying of Eastern oyster (Crassostrea virginica) seed for growout in S.F. Bay 1889 1.5 thousand mt of seed imported 1899 1,100 mt of oyster meat produced 1908 Down to ~ 600 mt of oyster meat 1921 Seed shipments discontinued 1939 Holding of imported stock halted 11
C. virginica on the Pacific Coast Limited natural reproduction spawning temperature ~ 25oC As S.F. Bay becomes polluted growout shifted to Washington 1883 railroad reached Willapa Bay 1897 WWI large Eastern oyster relay industry in Washington 1919 Eastern oyster stocks suffered a massive mortality (unknown cause) 12
Crassostrea gigas the Japanese or Pacific oyster C. gigas Native oyster Ostea conchaphila 13
Crassostrea gigas Japanese or Pacific oyster broadcast spawner > 16 ppt growth 10-30 oc will withstand < 0o C withstands periods of turbid water conditions CA problem - requires temperatures greater than 20o C for spawning 14
Bottom Culture of Spat on Cultch Extensive culture minimal care 15
Development of Hatcheries U.S. West Coast 1980 s 1. Cost of Japanese spat was rising 2. Infrequent natural spawning of C. gigas 16
Lots and lots of algae 17
Broodstock Broodstock is conditioned for 2-6 weeks flow through trays fed algae 30% males (1.5-2 years old); 70% females (2.5 years and older) Female produces millions (60-90) eggs Salinity - above 20 ppt Water temp. - ~ 20oC Spawning Presence of gametes in the water Temperature shock Blender technique 18
Oyster Life Cycle D-stage veliger larvae Late veliger or eyed larvae 19
Eyed Larvae Larvae ready to be set (~ 2 weeks) are placed in tanks with bags of cultch Eyed larvae Bags of cultch 20
IMPACT OF HATCHERIES remote setting 21
I. Growout of Spat on Cultch Extensive culture minimal care Either on-bottom or off-bottom culture (stake) 22
II. Cultchless spat spat settled on crushed oyster shell (micro-cultch) 23
Nursery Spat can be placed in protected intertidal zones to grow and harden for several months. Exposing the spat to the air periodically hardens the shell and reduces predation 24
Cultchless Growout Rack and bag As the oysters grow, they are sieved; reduced in density and moved to larger mesh bags. Typically, a series of five bags with the last bag having a 5/8-inch mesh and holding 200-225 oysters Oyster density, size, and shape as well as predators and fouling are controlled. 25
Triploid Triploid oysters that can not reproduce are produced in a hatchery. Triploid oysters grow faster than normal diploid oysters and have good flavor (high glycogen content) during the summer spawning season. gonad Spawning glycogen cycle glycogen (animal starch) levels build up during the winter glycogen declines as it is used at the raw material for gonadal components in the early spring and summer 26
Oyster Harvest Off-bottom cultured in bags, trays and on ropes are often harvested mechanically because of their weight. 27
HARVEST OF OYSTERS Bottom culture (3 years) 28
Off-bottom culture in California 4" oyster in 13-18 months 29
Review of oyster industry - intensive phase 30
Review of oyster industry extensive phase 31
Oyster stake culture - 32
Cultchless (rack & bag) 33
Production Varies dramatically depending on bay or area being cultivated and exact details of culture process as to how closely the growout units are spaced. Bottom culture = 50 mt/ha (~25 kg/bushel & ~ 2000 bushels/ha) Stake culture = 140 mt/ha (14 kg/m2) 34
Live Meat is ~ 15% of the whole Pacific oyster weight Shucked (live) Canned Fresh on half shell (live) Frozen on the half shell 35
Problems with free food Vibrio vulnificus parasitic bacterium that infest oysters and causes lethal septicemia in individuals with impaired immune systems. 4 deaths in California in 2000. A significant problem in Gulf Coast oysters. FDA is considering pasteurization (cooking) to be required of all Gulf Coast oysters. 36
Problems with free food (cont.) Toxic algae consumption of several species of algae containing toxic algae can lead to high levels of the toxins in oysters. Paralytic shellfish poisoning and amnesic shellfish poisoning are the two most common on the Pacific coast. Monitored by the individual states Department of Health using the mouse assay. Note: cooking does not destroy these algal toxins 37
Shellfish Regulation Food Safety National Shellfish Sanitation Program (NSSP) under the FDA Requires that both farmed and wild harvest growing areas be distinctly demarcated Each growing area tested for pathogens and classified as to water quality as determined by fecal coliform counts 38
Classification of Growing Areas Approved areas highest water quality, allowing harvest at all times Conditionally approved areas where fecal coliforms levels spike above the maximum level during or after storm events, harvest allowed at other times Tomales Bay, CA Restricted area where fecal coliforms levels are routinely higher that the maximum level allowed and requires products to be relayed out to an Approved or Conditional area to purge for several months Prohibited - areas in proximity to sewer outfalls, marinas, industrial effluent discharge areas or other potential sources of contamination 39
Food Safety (cont.) NSSP requires harvesters to use tags on each container of shellfish which lists the company name, harvest location and date Interstate Shellfish Sanitation Conference (ISSC) was formed in 1982 to foster and promote shellfish sanitation through the cooperation of state and federal control agencies, the shellfish industry, and the academic community 40
CDF&G California Department of Fish and Game is the lead agency for aquaculture Each aquaculture facility including oyster growers must submit an annual registration with the department and maintain sales and production records for inspection Leases tidelands to oyster growers $ 2.00/arce plus a privilege tax of $ 0.04/packed gallon of oysters (1 bushel of oysters = 1 gallon of meat) Lease holder has exclusive right to cultivate and harvest aquatic organisms in the lease area 41
State Department of Health California Department of Health Service certification of growing areas; monitoring for the occurrence of biotoxins and approves facilities used for handling, shucking, and marketing shellfish Oregon and Alaska have similar programs 42
Local Oyster Companies http://drakesbayfamilyfarms.com/ http://tomalesbayoysters.com/ http://www.hogislandoysters.com/ 43