Evaluating the influence of cage motion on the growth and shell characteristics of oysters (Crassostrea virginica) among several gear types

An influx of new oyster culture gear provides growers with an expanded ability to grow oysters throughout the water column. Each gear type is exposed to a different regime of physical forces, which is thought to affect oyster production differently; however, there is a poor understanding of the physical conditions inside cages and how they influence the production rate and quality of oysters. A greater understanding of the fundamental relationships between cage motion, oyster growth, and shell shape could help to improve the efficiency of off-bottom oyster production. Such understanding is critical for tailoring gear selection and tuning gear performance to suit grower needs. To address this void, cage motion, internal oyster movement, and oyster growth among three common cultivation methods (Virginia-style bottom cages, Seapa (R) long-line baskets, and floating cages) were monitored over a single growing season to clarify the role of the physical environment on oyster performance (shell and tissue growth). The averages and variance in motion among each cultivation method were noticeably different, which resulted in significant differences in the growth rate and quality of oysters they produced. Movement of the floating cages and long-line baskets could largely be explained by wind waves generated from a single direction in the field (r2 = 0.49, r2 = 0.36, respectively), while bottom cage movement was far less affected by wind waves. The changes in physical conditions inside each cultivation method demonstrated a trade-off between shell growth rate (a metric of time to market) and shell and meat quality (representative of crop value). These results can help inform growers wishing to strategically adopt cultivation methods that are most aligned with their production goals.