Growth, morphometrics, and nutrient content of farmed eastern oysters, Crassostrea virginica (Gmelin), in New Hampshire, USA.

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 geographic range of the eastern oysters is lacking. The present study was designed to quantify the relationships among various metrics of farmed eastern oysters near its northern geographic range focusing on nutrient content. Hatchery-reared oysters were deployed in polyethylene bags at six sites, and were measured on multiple occasions from 2010-2012. A quadratic 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 yr, and 'regular' size (76 mm) would require 3 yr. 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.

Long-term seafloor monitoring at an open ocean aquaculture site in the western Gulf of Maine, USA: development of an adaptive protocol.

The seafloor at an open ocean finfish aquaculture facility in the western Gulf of Maine, USA was monitored from 1999 to 2008 by sampling sites inside a predicted impact area modeled by oceanographic conditions and fecal and food settling characteristics, and nearby reference sites. Univariate and multivariate analyses of benthic community measures from box core samples indicated minimal or no significant differences between impact and reference areas. These findings resulted in development of an adaptive monitoring protocol involving initial low-cost methods that required more intensive and costly efforts only when negative impacts were initially indicated. The continued growth of marine aquaculture is dependent on further development of farming methods that minimize negative environmental impacts, as well as effective monitoring protocols. Adaptive monitoring protocols, such as the one described herein, coupled with mathematical modeling approaches, have the potential to provide effective protection of the environment while minimize monitoring effort and costs.