Supplementing Oyster Restoration with Direct Setting

Published: April 24, 2025

Summer of 2024 we generated a lot of buzz over our oyster larvae direct setting project. The project objectives include designing and testing a larval distribution system, demonstrating the efficacy of direct setting, deploying millions of oyster larvae, surveying survival rates and oyster density, and comparing direct setting to spat-on-shell techniques. This project is funded by an Oyster Innovation grant from Chesapeake Bay Trust and the Chesapeake Oyster Alliance. 

Direct setting has the potential to supplement traditional spat-on-shell restoration. It is intended to reduce the cost and effort of restoration because it does not involve transporting large quantities of shell and involves fewer steps of production. This has an added co-benefit in that direct setting produces substantially fewer carbon emissions as it can be done with smaller vehicles/vessels. 

Last year we successfully developed and tested a device to release oyster larvae directly onto a restoration reef, but low salinities throughout the bay caused problems with oyster larvae production, we opted to wait until this summer to deploy the larvae, hoping for better water conditions. Right now salinities in the lower part of the Severn are already in the 9-10 ppt range, which is on the high side for spring, so we are optimistic about being able to deploy this summer. Our goal is to plant at least 13 million larvae.

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The project builds on previous research, including proof of concept studies. We will expose the larvae to L-DOPA (a neurotransmitter that induces oysters to undergo metamorphosis) and safely convey them to the hard substrate of the Peach Orchard restoration reef. A battery-operated pump will intake ambient river water, intake larvae exposed to L-DOPA from on board the boat, and output the larvae at the bottom of the river at the reef. For a cool-sounding twist, we will also collaborate with Chesapeake Bay Foundation to use a kind of underwater loudspeaker (a hydrophone) to play recordings of healthy oyster reefs. Reefs, just like human cities, are actually pretty noisy places with fish and other critters making all kinds of sounds. There is growing evidence that the sound of a healthy reef facilitates oysters “striking” onto their substrates more effectively, and we want to give them every advantage we can.

To verify our success, we will perform scuba diving surveys on the reefs next year, with involvement from SRA staff, volunteer divers, and the Black Girls Dive Foundation. This project aims to accelerate restoration progress, reduce costs, and provide educational opportunities while promoting oyster population replenishment in the Severn River and broader Chesapeake Bay. Stay tuned to our newsletters to see how the work unfolds!