Abstract
Studying the larval dispersal of bottom-dwelling species is necessary to understand their population dynamics and optimize their management. The black-lip pearl oyster (Pinctada margaritifera) is cultured extensively to produce black pearls, especially in French Polynesia's atoll lagoons. This aquaculture relies on spat collection, a process that can be optimized by understanding which factors influence larval dispersal. Here, we investigate the sensitivity of P. margaritifera larval dispersal kernel to both physical and biological factors in the lagoon of Ahe atoll. Specifically, using a validated 3D larval dispersal model, the variability of lagoon-scale connectivity is investigated against wind forcing, depth and location of larval release, destination location, vertical swimming behavior and pelagic larval duration (PLD) factors. The potential connectivity was spatially weighted according to both the natural and cultivated broodstock densities to provide a realistic view of connectivity. We found that the mean pattern of potential connectivity was driven by the southwest and northeast main barotropic circulation structures, with high retention levels in both. Destination locations, spawning sites and PLD were the main drivers of potential connectivity, explaining respectively 26%, 59% and 5% of the variance. Differences between potential and realistic connectivity showed the significant contribution of the pearl oyster broodstock location to its own dynamics. Realistic connectivity showed larger larval supply in the western destination locations, which are preferentially used by farmers for spat collection. In addition, larval supply in the same sectors was enhanced during summer wind conditions. These results provide new cues to understanding the dynamics of bottom-dwelling populations in atoll lagoons, and show how to take advantage of numerical models for pearl oyster management.
Highlights
Understanding the population connectivity of marine species is necessary to fully comprehend population dynamics, community dynamics and structure, genetic diversity, and the resilience of natural populations to human exploitation [1]
Wind regimes Twelve wind regimes (WR) of 30 days each were identified with the clustering (Table 4)
The overall frequencies of each WR are between 4.9% (WR 12) and 13.3% (WR 8)
Summary
Understanding the population connectivity of marine species is necessary to fully comprehend population dynamics, community dynamics and structure, genetic diversity, and the resilience of natural populations to human exploitation [1]. Population connectivity is driven by interactions between organism physiology, morphology and behavior, and the biological and physical environments [2,3,4]. The main factors explaining spatial and temporal variability in recruitment are: (1) the larval supply, dependent on broodstock density, fecundity and spawning seasonality [5], (2) the larval dispersal, driven by the currents and organism behavior [6], (3) the larval development, primarily controlled by temperature and trophic resources availability [7], (4) the larval mortality, as a consequence of predation, physiological stress (e.g., temperatures, salinity or oxygen stress), disease and parasites [8], (5) the habitat suitability [9] and (6) postsettlement survival, which depends on delay of metamorphosis, biological and physical disturbances, hydrodynamics, physiological stress, predation, and competition [10]. Very few studies have used good validation and forcing data
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