Labor and grow-out gear are major expenses for commercial off-bottom oyster farms, making their efficient use critical for staying in business. Routine husbandry practices, such as splitting or thinning oysters into lower densities, must balance labor demands with effective gear utilization. While low stocking densities are shown to improve growth, tradeoffs with labor and gear are often overlooked. Additionally, research has not considered the potentially differing effects of initial stocking density from the density that triggers splitting. This farm-scale study standardized initial stocking density (10%) and evaluated the impacts of three different trigger densities (25%, 50%, and 75%) on time-to-market, growth metrics, survival, labor requirements, and gear utilization.
In April 2023, 27 FlipFarm baskets were stocked with ~25 mm oysters and deployed across three lines on the VIMS Research Farm in the York River, Chesapeake Bay (9 baskets per line). Baskets were haphazardly assigned to one of three trigger densities and monitored for growth, split once a treatment level reached the trigger volume, and restocked at 10% by size class, creating additional baskets as needed. By June 2024, the 25% trigger density had a 15.1% (± 3.95%) higher mean percent-to-market than the 75% trigger density (Fig 1). Surprisingly, percent survival did not differ between treatments. Market-sized oysters from the 75% trigger density had a 2.8mm (± 1.04) greater shell height but a 1.5% (± 0.06%) smaller cup ratio than those from the 25% density. In contrast, condition index and dry tissue weight did not differ between treatments. Regarding labor needed and gear use throughout the study, the 25% trigger density used 224 baskets and required 133.5 hours of labor, the 50% density used 185 baskets and 112 hours, and the 75% density used 63 baskets and 58 hours (Fig 2). For farmers, a lower trigger density could offer faster returns but comes at a higher labor cost, while a higher trigger density could reduce labor expenses but delay market-ready yields. These findings highlight the critical tradeoffs in strategies for this ubiquitous husbandry practice, encouraging off-bottom farmers to reevaluate their splitting techniques to maximize profitability and ensure long-term financial stability.