Abstract
Fisheries and aquaculture industries worldwide remain reliant on seed supply from wild populations, with their success and sustainability dependent on consistent larval recruitment. Larval dispersal and recruitment in the marine environment are complex processes, influenced by a multitude of physical and biological factors. Biophysical modelling has increasingly been used to investigate dispersal and recruitment dynamics, for optimising management of fisheries and aquaculture resources. In the Fiji Islands, culture of the black-lip pearl oyster (Pinctada margaritifera) is almost exclusively reliant on wild-caught juvenile oysters (spat), through a national spat collection programme. This study used a simple Lagrangian particle dispersal model to investigate current-driven larval dispersal patterns, identify potential larval settlement areas and compare simulated with physical spat-fall, to inform targeted spat collection efforts. Simulations successfully identified country-wide patterns of potential larval dispersal and settlement from 2012–2015, with east-west variations between bi-annual spawning peaks and circulation associated with El Niño Southern Oscillation. Localised regions of larval aggregation were also identified and compared to physical spat-fall recorded at 28 spat collector deployment locations. Significant and positive correlations at these sites across three separate spawning seasons (r(26) = 0.435; r(26) = 0.438; r(26) = 0.428 respectively, p = 0.02), suggest high utility of the model despite its simplicity, for informing future spat collector deployment. Simulation results will further optimise black-lip pearl oyster spat collection activity in Fiji by informing targeted collector deployments, while the model provides a versatile and highly informative toolset for the fishery management and aquaculture of other marine taxa with similar life histories.
Highlights
Ocean currents are a key physical feature of the marine environment, influencing species’ diversity, distribution, reproduction and abundance [1]
This study utilised hydrodynamic particle dispersal modelling to simulate the dispersal of black-lip pearl oyster larvae within the Fiji Islands over four years, and compared the results obtained with numbers of spat harvested from collectors during a previous study by Kishore et al [22]
While the dispersal model used during this study has provided unique insights into the potential larval dispersal patterns of P. margaritifera in the Fiji Islands, there remains substantial room for refinement of the model and simulation parameters
Summary
Ocean currents are a key physical feature of the marine environment, influencing species’ diversity, distribution, reproduction and abundance [1]. Larval dispersal and recruitment dynamics in the marine environment are complex, and governed by a multitude of physical, biological and behavioural variables including, but not limited to, source and sink location bathymetry, gamete release locations (pelagic vs benthic species), passive dispersal vs active larval swimming behaviour, pelagic larval duration (PLD), fecundity, larval survival, prevailing current regimes and larval homing abilities [7,9,10,11] Due to these factors, measuring larval dispersal, development and settlement during field studies presents many challenges, and the development of biophysical models has become increasingly important to understand larval transport and settlement pathways [11]
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