Direct Setting of Eastern Oyster (Crassostrea virginica) Larvae Confirmed with Calcein, a Fluorochrome Dye

Ongoing efforts to restore eastern oyster (Crassostrea virginica) populations in regions of low natural recruitment rely on stocking juveniles (spat shell) rebuild populations. Often, remote setting is used, entailing releasing hatchery-produced larvae into recirculating tanks filled with shells. Other restoration methods that C. virginica directly onto the shell situ, called “direct setting,” have shown promise but were unable definitively prove larval origin without use enclosures. The objective this study was determine if tagging calcein, a fluorochrome dye, could be viable method for confirming studies direct Chesapeake Bay. To do so, conditioned water from adult marked calcein and released by divers three 3.6-m2 research sites constructed bags during July 2019 September recovered after 7 days. All moved flow-through land spat subsample valves counted each bag 8–12 days deployment. Spat remaining 42 46 post A total 119,020 found 84 two deployments initial settlement counts conducted just recovered. viewed under blue light excitation (n = 84) contained tag, indicating these derived over reefs. Initial efficiencies ranged 0.1 3.4% September, respectively. salinities experienced below average may contributed reduced survival compared September. Shell zero 90 per shell. greatest closest where (87% 12% bags; high-count clustered around release locations). Overall, 6 out 190 deployed had estimates similar (hatchery) targets (10–20 values higher than hatchery targets. presence mark confirmed origin, together observed suggests there developing as stock enhancement technique. However, more work needed understand limitations technique, including its efficaciousness at larger scale.