Patterns in abundance, size and space-use of Giant Mud Crab (Scylla serrata) in a temperate marine protected area

Abstract

Marine Protected Areas limit fishing to protect a broad range of species and enhance biodiversity. Consequently, closures may not benefit species equally and species-specific assessments are required to determine the impact of closures. Relative abundance and size of Giant Mud Crab (Scylla serrata) was compared across no-take and fished zones in Port Stephens-Great Lakes Marine Park, on the temperate east coast of Australia (32.45°S). In addition, passive acoustic telemetry was used to estimate daily space-use areas. Similar abundances were observed between no-take and fished zones; however certain no-take sites had higher abundances than others. In addition, crabs were 9.9 mm larger in no-take zones on average. Daily crab space-use varied widely (~4 to 1000 m2), and generally increased with water temperature and conductivity. These patterns indicate that recruitment processes interact with marine park protection to shape crab abundances across estuaries. However no-take zoning appears to primarily limit fishing mortality on legal size crabs (i.e., carapace length >85 mm) resulting in larger crabs within no-take zones. This may mean no-take zones enhance reproductive output of crab populations since larger individuals are likely to be more fecund.