Simulating larval dispersal processes for abalone using a coupled particle-tracking and hydrodynamic model: implications for refugium design

Abstract

A coupled particle-tracking and hydrodynamic model, into which observed current data were assimilated, was used to simulate larval dispersal of large abalone (Haliotis discus discus, H. gigan- tea, and H. madaka) in Sagami Bay, Japan. The aims of this study were to (1) clarify larval dispersal pro- cesses and settlement sites, and (2) evaluate the existing harvest refugium and estimate the suitability of other areas for larval sources, using this model. In the larval dispersal simulations, particles were re- leased at the time of hatching, which was calculated from the estimated time of fertilization/potential spawning and based upon the water temperature. The results of larval dispersal simulations indicate 2 different dispersal patterns: (1) transport toward the coast after dispersal offshore, and (2) gradual dis- persal offshore. The refugium was compared with 3 hypothetical reproductive sources located 1 km north, west, and south of the refugium. During settlement competency, transport success (transport to the area at the depth of adult habitat: ≤ 30 m) of particles released at the refugium was highest (27 to 75%), and suggested that the location of this refugium was more suitable for a larval source than those of the hypothetical reproductive sources. Multiple potential larval settlement sites were identified. These results have important implications for refugium design at the study site. The method and model devel- oped in the present study could be used for evaluating harvest refugia and for identifying effective lo- cations for reproductive sources and potential settlement sites.