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April 14, 2013

 

United States

Virginia—Grow Oysters on Shrimp Waste

 

From Abstract: The objective of these experiments was to determine if oysters (Crassostrea virginica) could be grown in a recirculating system containing artificial seawater (made from well water and Crystal Sea synthetic sea salts) and if shrimp waste (feces and uneaten feed) could be used to feed them.

 

The first experiment was a twelve-week growout study.  Approximately 7,000 oysters were stocked in a single layer in four, six-foot diameter tanks partially filled with 3,200 liters of water.  The system was connected to a 4,000-liter storage tank and twelve, 1,000-liter algae culture tanks.  Two species of marine microalgae were grown as oyster feed, a diatom (Chaetoceros spp.) and a dinoflagellate (Isochrysis spp.).  The number of algae cells batch fed daily and ion chemistry were monitored.  Calcium supplementation was required to maintain suitable water conditions.  Overall, oyster survival remained greater than 99% and growth was steady among the 50 oysters that were monitored.  Length, width and thickness gained averaged 1.3, 1.1 and 0.33 mm per week, respectively.

 

The second experiment was a twelve week growout study conducted in nine zero-discharge, recirculating systems (70-liter tanks with a 14-liter, moving bed, nitrification reactor) with synthetic seawater.  Water was pumped from the oyster tank (receiving tank) into the bioreactor, which subsequently drained into the shrimp culture tank.  The system was designed to keep matter in suspension.

 

Treatment A consisted of bivalves only, 12 oysters on an elevated rack in the receiving tank.  They were fed Reed Mariculture shellfish diets.

 

Treatment B consisted of 15 shrimp in the shrimp tank, and the same oyster configuration described in Treatment A.  Shrimp were fed 8 grams of 2.4 mm sinking pellet shrimp feed (Zeigler Brothers) daily; no shellfish feed was included, therefore the only feed for the oysters was shrimp waste.

 

Treatment C combined treatments A and B, utilizing both feeding regimes.

 

Oysters grew twice as fast when fed shrimp waste only, compared to algae only or a blend of algae and shrimp waste.  Oyster survival rates were best when fed algae only.

 

These experiments demonstrated that oysters could be grown in recirculating systems using artificial seawater and shrimp effluent.

 

Source: The Thumb Drive Containing the Abstracts from Aquaculture 2013 (February 21-25, 2013, Nashville, Tennessee, USA).  Information: John Cooksey, World Aquaculture Conference Management, P.O. Box 2302, Valley Center, California 92082 USA (phone 1-760-751-5005, fax 1-760-751-5003, email worldaqua@aol.com).  Culturing Oysters in Zero-Exchange Systems Using Synthetic Seawater, Calcium Supplementation, and Shrimp Waste as Feed.  David Kuhn (email davekuhn@vt.edu, Department of Food Science and Technology, Virginia Tech, Blacksburg, Virginia 24061, USA), Dan Taylor and Matt Angier.  February 2013.

 

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