A Comparison of Drop Camera and Diver Survey Methods to Monitor Atlantic Sea Scallops (Placopecten magellanicus) in a Small Fishery Closure

Abstract

Large-scale fishing closures are a leading tool in the spatial management of global ocean resources. This is exemplified in the U.S. Atlantic sea scallop (Placopecten magellanicus) fishery which uses a rotational scheme of temporary closed areas in both offshore and nearshore waters. The closed areas are generally hundreds to thousands square kilometers, but a group of inshore commercial scallop harvesters were interested in the effect of closing a much smaller area (3 km2), which had sustained valuable harvest before recent poor yields. To describe changes in scallop abundance and size within and around this closure, two independent surveys, a drop camera and diver transect, were conducted through industry–academic collaboration. In addition, this unusual union of a predominately offshore method, the drop camera, and inshore method, divers, was used to better interpret the results of each method. The drop camera survey results suggested that the closure significantly increased the biomass of exploitable scallops, showing that even closure orders of magnitude smaller than commonly used for scallops can be effective. Although the dive survey did not show this, understanding the uncertainties of each method helped resolve this discrepancy. Drop camera densities were calculated from a broader spatial area more representative of the entire area with increased sample size. By contrast, the dive survey provided an intensive description of scallops at each individual survey site. Combining a drop camera survey with dive stations to collect scallop measurements would provide densities from a spatial scale representative of the study area while improving shell height frequency estimation and providing biological data. In addition, this project demonstrated how stakeholder engagement supported by academic institutions and fishery managers can allow intensive monitoring of small fishery closed areas outside of government assessments.