NCCOS scientists have recovered tagged oyster “spat” (juvenile oysters that have attached to a surface, such as other oyster shells) from a temporary test scale oyster reef in the adjacent waters to the Cooperative Oxford Laboratory, in Oxford, MD. Late-stage tagged oyster larvae were cued to settle and directly released by divers onto oyster shell bags. Recovered shell bags contained spat on shell, positively confirmed to be from the larvae released.
The project research team consists of leader Jason Spires (NCCOS), Stephanie Westby (NOAA Restoration Center), Cecily Steppe (U.S. Naval Academy), and James Dumhart (Piney Point Aquaculture Center).
In restoring oyster beds, oyster shell are sometimes seeded with larvae in enclosed tanks before returning the seeded shell to their natural habitat. A research team led by NCCOS has been working for more than a year to develop an experiment to study the feasibility of directly releasing oyster larvae onto unenclosed, open water, oyster reefs as a seeding mechanism as an alternative to the current restoration process.
One challenge is to determine definitively that spat found on the test-scale reef are actually the result of the released larvae—and not from naturally occurring larvae in the water column. NCCOS scientist Jason Spires recently developed a mechanism to mark late stage oyster larvae by placing them in a calcein (fluorescent dye) bath prior to release. The calcein dye mark fluoresces under certain light lengths, and can persist for several months as the larvae sets and grows into a juvenile oyster.
To test the calcein dye technique, Spires, with significant help from NOAA intern Sierra Hildebrandt, deployed three arrays of 32 shell bags in mid-July 2019 onto a Chesapeake Bay oyster sanctuary adjacent to Cooperative Oxford Laboratory, in Oxford, MD. Divers released 0.6 million hatchery- produced, marked oyster larvae onto the center of each array. The arrays were recovered a week later and moved ashore to flow-through holding tanks so any spat could be quantified and the calcein mark identified.
Did the research team find any marked spat? Yes! Continued analysis is under way, but early estimates are that the experiment produced thousands of oyster spat. All spat sampled showed calcein marks.
Shell bags near the center of each array, where the larvae were deployed, produced far more spat than bags further from the center. A replicate experiment is currently under way, with early results being even more encouraging then the July deployment. Although settlement results are promising, additional studies are warranted to investigate the scalability and applicability for large scale oyster restoration and aquaculture.
This project is in support of a request from the NOAA Restoration Center to investigate alternative oyster restoration strategies. Tagging methods utilized for larval origin confirmation build on methods developed in the NCCOS funded Oyster Marking Methodology Study.
For more information, contact Jason Spires.