Surfclam Survey Strategies

The Atlantic Surfclam (Spisula solidissima) has been surveyed by the Northeast Fisheries Science Center (NEFSC) since 1965, but many areas remain unexplored due to gear and funding limitations. The NEFSC modified commercial dredge survey samples from Cape Hatteras to Georges Bank, collecting data on the number of clams per tow over a 2.77 km transect. The SMAST video survey collects images of the seafloor, four quadrats per station, on a 2.77-5.56 km grid. These images record the presence of holes of burrowing species, such as surfclams and ocean quahogs (Arctica islandica), but cannot identify species directly. Surfclams and ocean quahogs appear to be separated by a depth contour varying with region and temperature. By identifying and counting holes in the video survey, we examined areas of surfclam and ocean quahog habitat and the contour between them. These data sets were combined into a comprehensive map of surfclam density on Georges Bank. Linking data from different survey designs is difficult but will bring each survey’s strengths to bear on a species’ assessment.