Integrating a Rapid Assessment Protocol (RAP) into monitoring of subtidal oyster reefs

Abstract

Accurate and efficient monitoring of oyster reefs is critical for fisheries management and restoration. However, monitoring subtidal reefs requires labor-intensive methods, such as sampling by SCUBA divers. A new Rapid Assessment Protocol (RAP) based on the collection of underwater imagery from random replicate points across a reef expands the toolkit for oyster reef monitoring. This study tests how the qualitative RAP compares to existing quantitative monitoring tools to inform approaches that combine methods and improve monitoring. We surveyed paired unrestored harvested reefs and restored sanctuary oyster reefs in the upper, middle, and lower Chesapeake Bay (United States) to compare the RAP to diver-collected oyster metrics across management types and salinities. At each site, we compared the RAP's categorical habitat scores (based on percent cover and relative reef height in images) with physical metrics from synchronous diver collections, including live oyster density and biomass, on the same reef quadrats (n=64). High RAP scores successfully captured high oyster density, biomass, reef height, rugosity, and multiple size classes. At lower RAP scores, the physical metrics often differed between RAP scores on unrestored harvested reefs, but not restored sanctuary reefs. This study highlights the value of underwater video in increasing monitoring efficiency with respect to time investment, while providing different habitat data than physical metrics. We describe how the RAP can be used in combination with more intensive, physical monitoring tools for restoration and fisheries management. The results of the RAP can inform oyster management in Chesapeake Bay and can be adapted for use worldwide.