reared at least to the straight hinge stage in 51 sepa- 

 rate cultures during the past year. These larvae, the 

 results of 40 spawning attempts, were used in a vari- 

 ety of rearing and setting experiments. The algal 

 culture facilities can now provide food on a year- 

 round basis and are capable of producing 150 liters of 

 dense algal culture every 24 hr. Research on the 

 feeding of adult oysters in being conducted to show 

 how the oyster utilizes available food energy. Pre- 

 liminary experiements have determined the caloric 

 content of cultured algae and have shown that an 

 oyster can assimilate at least 859f of the energy con- 

 tent in the food that it consumes. Research is also 

 being conducted on the bacteria associated with 

 supplemental feeding of oysters in closed systems. 

 and efforts to produce viable offspring from hybridi- 

 zation of the Eastern (or American) oyster, 

 Crassostrea virginica. and the Pacific oyster, C. 

 gigas. are continuing. 



A pilot-scale oyster hatchery at Newport, Oreg. , is 

 producing seed from Pacific and Kumamoto {C. 

 gigas). Olympid (Ostrea lurichi). and European fO. 

 edulis) oysters on a routine basis. Peak production in 

 the pilot hatchery approaches 1 million juveniles per 

 month. The seed is being raised by growers in 

 Oregon and Alaska, and is being used in a variety of 

 studies by Oregon State University researchers. 



Heritability studies have been completed on the 

 Pacific oyster, and parentage is controlled to selec- 

 tively breed for rapid growth, high meat production, 

 and low mortality. The growth of hatchery seed oys- 

 ters in warmed ocean water from power plant ef- 

 fluents is under evaluation. Successful cryogenic 

 preservation of oyster sperm at -196°C has allowed 

 self-fertilization of the Pacific oyster after natural 

 sex reversal for genetic studies. Improved larval 

 feeding schedules and diets have increased the suc- 

 cess of setting in the hatchery. 



In their program to advance the state-of-the-art in 

 oyster culture, biologists at the Virginia Institute of 

 Marine Sciences have developed two new methods 

 for obtaining free oyster spat (cultchless), one for 

 relatively clear estuarine areas and one for areas 

 which ha\e heavy siltation problems. In the first 

 method, the spat must be removed from the sub- 

 strate before sufficient new shell for permanent at- 

 tachment has been produced. The set takes place in 

 fiber glass salmon-egg hatching trays in complete 

 darkness, using filtered river water. The spat are 

 removed from the tray bottom, to which they have 

 temporarily attached, by a strong stream of river 

 water, yielding cultch-free spat. 



The second method delays the removal of the 

 newly set spat from the substrate for 18-21 days. 

 Setting is induced on Frosted Mylar- or Herculene. 

 A new setting tray was designed to hold the mylar 

 upright. The spat set on the upright mylar sheets, 

 thus avoiding most of the siltation and organic de- 

 tritus. The spat is removed from the mylar sheet by 

 simply shaking it over a container of river water. It is 

 then dipped up and down in the container, washing 

 the loose spat off. 



A team of researchers at the Darling Center. Uni- 

 versity of Maine, is investigating the feasibility of 

 culturing several species of marine organisms in the 

 colder waters of that region. Although research is 

 being conducted on the deep sea scallop and blue 

 mussel, most of the experiments to date in this new 

 program have been with cultchless European and 

 American oysters. Trays of the cultchless oysters 

 have been placed at many different locations in the 

 Damariscotta estuary (24 km long) and at 14 sites 

 along the coastline. These were selected to provide 

 as good a geographic and ecological spread as possi- 

 ble and are being monitored for growth, survival, 

 and presence of fouling organisms. In the first year, 

 growth response of European oysters was excellent 

 (to 10 cm) in even the most exposed coastal 

 locations. The data will be utilized to develop a 

 predictive model allowing assessment of the poten- 

 tial of the Maine coast for economically competitive 

 oyster culture. A cooperative pilot hatchery is being 

 started at Newcastle which may result in the estab- 

 lishment of a commercial operation. 



The Departments of Agricultural and Mechan- 

 ical Engineering of the University of Maine are 

 working on oyster rafting systems which will be 

 adaptable to this environment and compatible with 

 multiple use concepts. A pilot model of a submers- 

 ible raft has been constructed and will be field test- 

 ed in 1972. 



Several problems inherent in the culture of oysters 

 and clams are being investigated at the University of 

 Washington. The optimal horizontal spacing of oys- 

 ter cultches suspended from rafts in relation to 

 growth, mortality, and condition is being determined 

 and the local variation in the degree and type of 

 fouling organisms evaluated. The investigators are 

 also attempting to determine if bacteria are responsi- 

 ble for some of the summer oyster mortalities. They 

 are particularly interested in Vibrio and other types 



-' Reference to irade names does not imply endorsement by the 

 National Marine Fisheries Service. NO.AA. 



45 



