Setting and deploying hatchery-produced spat-on-shell on Louisiana public oyster reefs in Southeast Louisiana for oyster restoration

Emily F. Baukema and Erin L. Olson
Fisheries Research and Development Division, Office of Fisheries, Louisiana Department of Wildlife and Fisheries, Grand Isle, LA. [email protected]; [email protected]

In spring 2019 Louisiana experienced a historically high Mississippi River event, which led to increased volumes of freshwater overwhelming oyster reefs. Prolonged periods of freshwater can cause oyster mortality, resulting in devastating losses for not only the oyster population, but also the industry. In a test effort to restore Louisiana public oyster reefs, the Louisiana Department of Wildlife and Fisheries focused on producing diploid pediveliger larvae for setting on oyster shell, and then deploying the spat-on-shell in bays within Southeast Louisiana. Deploying spatted cultch material may be more beneficial for restoring or enhancing areas rather than deploying plain cultch. A couple goals for planting spat-on-shell on public oyster grounds included creating broodstock sanctuary sites and replenishing public seed grounds with oyster stock. A broodstock sanctuary site is an off-limits site for oysters to mature and produce larvae that will recruit onto a nearby public reef. Methods for spat-on-shell production included bagging 3,787 shellbags with recycled oyster shells, provided through the Coalition to Restore Coastal Louisiana’s oyster shell recycling program. The Michael C. Voisin Oyster Hatchery (Grand Isle, LA) produced approximately 231 million diploid pediveliger larvae for setting onto shell. Setting tanks were located at the Fisheries Research Lab (Grand Isle, LA). After allowing the larvae to set for approximately 72 hours, the spat-on-shell were deployed. An estimated 40 million spat were deployed at nine deployment sites between April and August 2019. Deployment sites included plots within Hackberry Bay, Barataria Bay, and Breton Sound (Figure 1). LDWF staff from Coastal Study Areas 1 and 3 are monitoring the sites for spat growth and survival, final results are pending.