Modelling regional and local-scale larval seeding strategies for abalone (H. midae) ranching in South Africa

Understanding connectivity between abalone populations and residence times for pelagic larvae within suitable settlement habitats is critical sustainable management of wild stocks ranching schemes. In the Eastern Cape region South Africa, poaching has severely depleted Haliotis midae populations. Rebuilding stock through larval seeding being considered as a potentially viable method, though hampered by limited understanding habitat dispersal, both at regional local scale. To address this shortcoming, we apply multi-scale approach to investigate potential dispersal along coastline Cape, examining intra- inter-site connectivity, with primary focus nearshore scale (< 40 m water depth) where surf zone processes have strong influence. Delft3D applied (400-km domain) XBeach used (5-km model known Recife high-resolution (5-m cell size). Models were validated using field observations. Complex topo-bathymetry data local-scale domain around obtained state-of-the-art low-cost multi-method surveying approach. At scale, sites be connected across distances 50–100 km. However, large sandy embayment (Algoa Bay; 100-km arc length) likely present an obstacle transport in all but most extreme sustained wind wave forcing conditions. The central area act either self-seeding or meta-population site, depending on Recife, shallow gullies, under lower-energy waves, was determined optimal release point maximise residency preferred rocky, subtidal H. midae. Competent released are predicted order magnitude greater than randomly seeded larvae. This study provides site-specific time information fishery, more generally it novel method aid planning managing enhancement programs that could other locations.