Aquaculture 2022

February 28 - March 4, 2022

San Diego, California

DESIGNING AND EVALUATING WIRE-BASED STRUCTURES FOR THEIR ABILITY TO RECRUIT OYSTERS Crassostrea virginica AND STABILIZE SHORELINES IN COASTAL SOUTH CAROLINA, USA

 

Graham A. Wagner*, Gary W. Sundin, Greg K. Rothman, and Peter R. Kingsley-Smith

 

Shellfish Research Section

Marine Resources Research Institute

South Carolina Department of Natural Resources (SCDNR)

217 Fort Johnson Road, Charleston, SC 29412

wagnerg@dnr.sc.gov

 



In coastal South Carolina, the wild population of Eastern oysters (C. virginica )  consists primarily of extensive (>5,000 acres) intertidal reefs. This population is characterized as substrate-limited, where levels of natural recruitment are high but the presence of suitable substrate for settlement limits population growth. Since 2001 , the SCDNR has therefore focused its restoration efforts  on  substrate supplementation, primarily by deploying natural oyster shell in the intertidal zone to facilitate  oyster  settlement. In addition to providing habitat to a diversity of other organisms, t hese oyster-based living  shorelines support sediment capture and  the subsequent seaward expansion of  marsh vegetation . As oyster shell becomes increasingly costly and limited in supply, however, researchers continue to  explore alternatives to address the issue of substrate limitations without using natural oyster shell.

In 2011, t he SCDNR began utilizing wire-based structures for oyster restoration and shoreline protection. Initially, these structures took the form of repurposed (e.g., cement-coated)  crab traps (RCTs),  derived from derelict and abandoned traps in the environment,  in part as a solution to marine debris issues related to derelict fishing gear in the environment. In 2016, b ased on the success of RCTs, researchers began developing new approaches to living shoreline installations using purpose-built manufactured wire reefs (MWRs) intended to support high levels of oyster recruitment and  facilitate shoreline stabilization and habitat creation.

Over the past five years, these  MWR  structures have been installed on estuarine intertidal shorelines and monitored for various metrics of  performance  success to quantify their  ability to  provide ecosystem services by serving as living shorelines . Monitoring results presented here will support the abilities of these MWR structures to quickly recruit new oysters (see Figure 1) ,  accumulate landward sediment, and facilitate the expansion of  natural  marsh habitat through  vegetative growth. These findings are helping to support new state of South Carolina science-based regulations for living shorelines with a goal being to broaden their adoption as a shoreline protection strategy.