ANS18-10-L17-OYST-CULT

ANS18-10-L17-OYST-CULT - Veterans Day holiday Thursday,...

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Unformatted text preview: Veterans Day holiday Thursday, Nov. 11 • No discussion – Thursday Nov. 11 or Friday Nov. 12 • Read for the fun of it “Clamelot” Oysters Oysters ANS - 18 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 • Oysters = 4,164,000 mt (10% animal aquaculture) • Other mollusks = 1,690,000 mt including – (22,000 mt pearl oysters) & (247,000 mt freshwater mollusks) Oysters Oysters ANS - 18 2 – Japanese oyster* = 4,034,000 mt (97%) OYSTER AQUACULTURE Oysters Oysters ANS - 18 3 Aquaculture systems classification Extensive “animals/area” few many Intensive Extractive nature Oysters Oysters ANS - 18 Input-dependent “food source” man 4 Oysters Of all the oysters produced 4,400,000 mt or 97 % are a single species – the Japanese oyster (Crassotrea gigas) Why is this? Oysters Oysters ANS - 18 5 CALIFORNIA OYSTER INDUSTRY Oysters Oysters ANS - 18 6 THE WORLD RUSHES IN Middle of 1848 ~ 14,000 7500 Californians 6500 Americans End of 1849 ~100,000 Oysters Oysters ANS - 18 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 Oysters Oysters ANS - 18 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 Oysters Oysters ANS - 18 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 Oysters Oysters ANS - 18 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 Oysters Oysters ANS - 18 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) Oysters Oysters ANS - 18 12 Crassostrea gigas the Japanese or Pacific oyster C. gigas Native oyster Ostea conchaphila Oysters Oysters ANS - 18 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 Oysters Oysters ANS - 18 14 Bottom Culture of Spat on Cultch Extensive culture – minimal care Oysters Oysters ANS - 18 15 Development of Hatcheries U.S. West Coast – 1980’s 1. Cost of Japanese spat was rising 2. Infrequent natural spawning of C. gigas Oysters Oysters ANS - 18 16 Lots and lots of algae Oysters Oysters ANS - 18 17 • Broodstock is conditioned for 2 - 6 weeks flow• • • • Broodstock 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 Oysters Oysters ANS - 18 18 Oyster Life Cycle “D-stage” veliger larvae Oysters Oysters ANS - 18 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 Oysters Oysters ANS - 18 20 IMPACT OF HATCHERIES “remote setting” Oysters Oysters ANS - 18 21 I. Growout of Spat on Cultch Extensive culture – minimal care Either on-bottom or off-bottom culture (stake) Oysters Oysters ANS - 18 22 II. Cultchless spat spat settled on crushed oyster shell (micro-cultch) Oysters Oysters ANS - 18 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 Oysters Oysters ANS - 18 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 Oysters Oysters Oyster density, size, and shape as well as predators and fouling are controlled. ANS - 18 25 Triploid Oysters 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 Oysters Oysters ANS - 18 26 Oyster Harvest Off-bottom Oysters cultured in bags, trays and on ropes are often harvested mechanically because of their weight. Oysters Oysters ANS - 18 27 HARVEST OF OYSTERS Bottom – culture (3 years) Oysters Oysters ANS - 18 28 Off-bottom culture in California 4" oyster in 13 - 18 months Oysters Oysters ANS - 18 29 Review of oyster industry - intensive phase Oysters Oysters ANS - 18 30 Review of oyster industry – extensive phase Oysters Oysters ANS - 18 31 Oyster stake culture - Oysters Oysters ANS - 18 32 Cultchless (rack & bag) Oysters Oysters ANS - 18 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) Oysters Oysters ANS - 18 34 Live Shucked (live) Meat is ~ 15% of the whole Pacific oyster weight Fresh on half shell (live) Frozen on the half shell Canned Oysters Oysters ANS - 18 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. Oysters Oysters ANS - 18 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 ANS - 18 Oysters Oysters 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 Oysters Oysters ANS - 18 38 • Approved areas – highest water quality, allowing harvest at all times Classification of Growing Areas • 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 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 marinas, industrial effluent discharge areas or other potential sources of contamination ANS - 18 39 • Restricted area – where fecal coliforms levels are • Prohibited - areas in proximity to sewer outfalls, Oysters Oysters 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 ANS - 18 Oysters Oysters 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 Oysters Oysters ANS - 18 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 Oysters Oysters ANS - 18 42 Local Oyster Companies http://drakesbayfamilyfarms.com/ http://tomalesbayoysters.com/ http://www.hogislandoysters.com/ Oysters Oysters ANS - 18 43 ...
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This note was uploaded on 03/26/2011 for the course ANS 18 taught by Professor Mchenry during the Spring '11 term at UC Davis.

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