Oyster reef restoration projects often focus on planting cultch and occasionally seeding of hatchery-reared spat on shell requiring large-scale logistical efforts. Traditional methods frequently include seeding of fresh set spat to restoration locations. Consequently, high mortality has been observed due to predation and sedimentation. The Auburn University Shellfish Lab (AUSL) is conducting a three-year oyster reef restoration in Little Dauphin Bay (LDB), AL utilizing aquaculture techniques to improve survival and remove logistical concerns by using smaller setting material.
Six paired plots (750m2) were cultched with oyster shell in LDB followed by seeding of spat clusters on one plot per pair (shell height=25mm). Spat clusters are produced by setting pediveliger oyster larvae on small shell at the AUSL hatchery and then moved to an AUSL oyster farm. At the farm, aquaculture gear is used to accelerate growth and protect spat from predation prior to planting seed on plots. Three sets of paired plots are trapped for oyster drills to analyze predator mitigation. Plots are assessed semi-annually for differences in oyster populations between seeded and non-seeded plots and predator mitigation effects.
At the project midpoint (October 2022), 897,600 oysters were planted with deployments continuing through Fall 2023. Sampling indicates a bi-modal distribution of oysters suggesting two recruitment classes, but no significant population difference is currently observed between seeded and non-seeded plots. Oyster drills appeared on reefs in March 2022 with trapping efforts showing little effect on oyster populations. Sampling of plots through Spring 2024 will determine overall interaction of seeding and trapping in enhancement of restored oyster populations.