Modelling transport of larval New Zealand abalone (Haliotis iris) along an open coast

Abstract

The dispersal and transport of larval New Zealand abalone Haliotis iris was simulated using coupled two-dimensional hydrodynamic and Lagrangian particle-trajectory models. The aim was to estimate pelagic larval dispersal potential along the open coast, as a starting point from which basic management questions can be made for this recreationally and commercially important species. Larval dispersal was simulated from representative spawning sites under a range of representative hydrodynamic conditions, including wave-induced circulation cells. Larval presence over near-shore reef habitat declined as the energy of the flow field and corresponding larval dispersal and transport increased. Thus, spawning during high-energy conditions will promote dispersal and transport but reduce successful recruitment on near-shore reefs. This indicates that seeding of the adjacent coast is likely to be sporadic, with existing populations necessarily being somewhat self-recruiting. Results suggest that an ideal management system would ensure that adult populations were maintained at intervals of 10–30 km along the coast to maintain larval supply to areas in between. Dispersal characteristics were specific to the release site, and the simulations suggest that marine reserves can be positioned to accordingly achieve desired functions: for example, optimal choices can be made for seeding areas, recruitment or self-maintaining areas.