Presenter: Amanda Pysher (Old Dominion University)

Description:
Alternative substrates are increasingly used for oyster reef restoration. Our objective was to asses eastern oyster recruitment and size on the alternative substrates Oyster Castles (OC) and Grow Tiles (GT). Measures of success included high oyster recruitment, large size, and high benefit-cost ratios (BCR). We looked at four sites around the Chesapeake Bay in Virginia: Cherrystone, Mockhorn Bay, Lynnhaven, and Elizabeth. At each site, ten OC and ten GT were randomly interspersed in a line in the intertidal zone. All sites were sampled in October 2019, July 2020, and June 2021. The June 2021 and combined data (2019-2021) were analyzed using combinations of response variables and the factors year, site, and substrate type. Overall, OC had greater success than GT for recruitment and BCR. The live recruitment was greater on OC in June 2021 and combined across years, with mean densities of 518.82/m² to 599.55/m². Mean oyster heights were typically greater on GT for both data sets, both substrates had multiple cohorts, and growth was approximately 60-70 mm over the three years. Each year, because OCs are much less expensive than GT, the BCR was ten times greater on OC than GT, but the ratio did not include transportation, labor, or management costs. Many response variables were significantly different by site, with Mockhorn having the highest densities. Overall, both substrate types were successful in recruiting oysters and growing them to adult size. Further research on artificial substrates could be extended to analyze the substrates over a longer period of time, consistent sampling times, or and to examine mechanisms behind variations among sites.