Developing strategies to optimize shell growth performance and quality of near market size oysters
The aim of this project is to increase the state of knowledge with regards to the management of near market-size oysters grown in suspended culture in order to improve net productivity and economic viability. The overall objective of this study is to document the annual shell growth of various size classes of near market-size oysters and evaluate strategies to augment the proportion of saleable product.
The first objective is to document the annual shell growth of near market-size oysters in the St-Simon Bay area. Two locations will be selected and triplicate groups of 15 labeled oysters belonging to four size classes (49-51 mm; 54-56 mm; 59-61 mm; 64-66 mm) will be measured and deployed in floating bags and on oyster tables on May 1 2007. Shell height, length, depth and weight will be measured initially and at the end of the year. Shell height will be measured every two weeks until July 1 and every month thereafter until November 1. This work will be replicated in 2008 as a means of understanding the shell growth patterns of the various size classes.
The second objective will be to evaluate the effectiveness of brine dipping for liminating various fouling organisms including oyster spat, barnacles, and mussels. At present, most growers deal with these organisms during the annual grading or classification of their near market-size product. Mussels are typically removed either by hand or mechanically during the grading process, whereas barnacles and oyster spat must be removed by hand-scraping individual oysters. As a final step, many growers now dip their oyster stock in a saturated brine solution to eliminate boring sponge (Cliona celata) infection. It is possible that the same brine solution, if employed at the appropriate time, might serve to eliminate young oyster, mussel and barnacle settlement.
The third objective will be to evaluate different commercial grow-out strategies to augment the annual production of market-size oysters. At present most growers either hand-grade or mechanically grade all their stock at some point in the growing season. Although the timing of this activity may not be critical for <50-mm oysters, anecdotal observations suggest that larger individuals may require a more sophisticated handling protocol to maximize their net shell growth. This study will compare the yield of market-size product over a 2-y grow-out period using the existing strategy versus two alternative strategies. Existing strategy: Spring/summer grading - >50-mm oysters are mechanically graded in June-July and transferred to clean bags in order to ensure access to food resources. Optional strategy:
- No grading - >50-mm oysters are left in the bags and fouling organisms are eliminated via bag flipping and brine dipping. Optional strategy
- Fall grading - >50-mm oysters are treated for fouling organisms during the summer and then mechanically graded in early September.
2007 - 2009
Atlantic: Gulf of Maine, Scotian Shelf
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