Comparison of Visual Surveys Versus Dredging for Monitoring Bay Scallops (Argopecten irradians) in Seagrass Beds

Patterns and Processes Underlying Spatiotemporal Variation in Bay Scallop (Argopecten irradians concentricus) Density and Size Structure within Three North Carolina Sounds

“…Bay scallop densities and sizes in seagrass beds in southern Core Sound, Back Sound, and Bogue Sound, NC, were assessed with visual search methods using snorkel along 5 min transects and were adapted from Lyon et al (2021).…”

“…Bay scallops, Argopecten irradians irradians (Lamarck 1819) and Argopecten irradians concentricus (Say 1822), were once abundant throughout the coastal eastern United States and were a profitable commercial and recreational fishery (MacKenzie 2008, Shumway & Parsons 2016). Adult and juvenile bay scallops prefer to live within seagrass habitats (Carroll et al 2010, 2012, Hernández Cordero et al 2012, Lyon et al 2021 and references therein). Bay scallops in North Carolina (NC) ( Argopecten irradians concentricus ) live for approximately 1–2 y and spawn primarily from August to January, with a second shorter spawning period during March through May (Shumway & Parsons 2016).…”

“…Dredges, although often the most efficient method for sampling shallow marine habitats, can be detrimental to and disturb benthic habitats by uprooting seagrass, displacing juvenile bay scallops, as well as collecting accidental bycatch of other species, such as juvenile fish and crabs (Bradshaw et al 2001, Bishop et al 2005). Visual survey methods by divers on snorkel and SCUBA have been used in other studies for monitoring the abundance of bay scallops in lieu of using a dredge (Stephenson & Geiger 2010, Tettelbach et al 2011, Lyon et al 2021). There is a significant need for updated information on the distribution and abundance of bay scallops in NC to better inform potential fishery harvests in areas where scallops may be recovering, as well as to help design annual population sampling programs, and potential stock-enhancement restoration efforts (NCDEQ 2017).…”

“…In a recent study, the efficacy of visual surveys for quantifying bay scallop density and distribution in seagrass beds in Back Sound, NC was compared among three different visual search time periods using snorkel transects (5, 10, and 20 min), as well as compared with dredging (Lyon et al 2021). There was no significant difference in scallop density and the catch-per-unit-effort (CPUE) among visual survey time treatments.…”

“…There was no significant difference in scallop density and the catch-per-unit-effort (CPUE) among visual survey time treatments. Scallop densities observed during visual surveys were three times higher than densities using a scallop dredge, and scallop CPUE was five times higher using a scallop dredge compared with visual surveys (Lyon et al 2021). If visual surveys indicate the true natural density of bay scallops in this study system, then the dredge sampling efficiency for evaluating bay scallop density was 33%.…”