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Growth, morphometrics and nutrient content of farmed eastern oysters, Crassostrea virginica (Gmelin), in New Hampshire, USA
Grizzle, R., K. Ward, C. Peter, M. Cantwell, D. Katz, AND J. Sullivan. Growth, morphometrics and nutrient content of farmed eastern oysters, Crassostrea virginica (Gmelin), in New Hampshire, USA. Aquaculture Research. John Wiley & Sons, Inc., Hoboken, NJ, 48(4):1525-1537, (2017).
This study increases the geographical range of research on the nutrient content of farmed oysters to northern New England. Data are now available from Alabama in the Gulf of Mexico to New Hampshire. Focusing on N content of farmed oysters, the following conclusions seem reasonable based on research to date. Considering all studies to date, the N content of farmed oysters may be expected to vary widely around the average values, and is likely affected by environmental conditions, oyster age/size, and physiological changes in the oyster that occur seasonally. Based mainly on this study, %N content was highest in oysters grown in water that likely had the highest average dissolved inorganic N concentrations. These findings suggest several areas for future research. More studies are needed on how oyster nutrient content is affected by ambient environmental conditions, different farming methods, different sizes of oysters, and oysters harvested at different times of the year.
When harvested, oysters represent a removal from the ecosystem of nutrients such as nitrogen (N)and carbon (C). A number of factors potentially affect nutrient content, but a quantitative understanding across the geographical range of the eastern oysters is lacking. This study was designed to quantify the relationships among various metrics of farmed eastern oysters near its northern geographical range focusing on nutrient content. Hatchery-reared oysters were deployed in polyethylene bags at six sites, and were measured on multiple occasions from 2010 to 2012. Aquadratic polynomial fit to the combined datasets for shell height indicated that on average a ‘cocktail’size oyster (63 mm shell height) would be reached after 2 year, and ‘regular’ size (76 mm) would require 3 year. There were significant differences in growth rates and oyster nutrient content among the sites; means for %N in soft tissue ranged from 6.9 to 8.6, and 0.07 to 0.18 in shell. Percent N in soft tissue and shell were highest at two sites at the mouths of rivers with elevated dissolved inorganic N concentrations in the water. Grand means (all sites, seasons and years combined) of soft tissue N and C for regular size oysters were 7.3% and 38.5%, respectively; and for shell N and C were 0.13% and 12.0% respectively. Our study extends the range of data on nutrient content of the eastern oyster to northern New England, and indicates that oyster size, seasonality,and nutrient concentration in ambient water potentially affect %N and %C content of oysters.