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Many marine animals have a biphasic life cycle in which demersal adults spawn pelagic larvae with high dispersal potential. An understanding of the spatial and temporal patterns of larval dispersal is critical for describing connectivity and local retention. Existing tools in oceanography, genetics, and ecology can each reveal only part of the overall pattern of larval dispersal. We combined insights from a coupled physical-biological model, parentage analyses, and field surveys to span larval dispersal pathways, endpoints, and recruitment of the convict surgeonfish Acanthurus triostegus . Our primary study region was the windward coast of O‘ahu, Hawai‘i. A high abundance of juvenile A . triostegus occurred along the windward coast, with the highest abundance inside Kāne‘ohe Bay. The output from our numerical model showed that larval release location accounted for most of the variation in simulated settlement. Seasonal variation in settlement probability was apparent, and patterns observed in model simulations aligned with in situ observations of recruitment. The bay acted as a partial retention zone, with larvae that were released within or entering the bay having a much higher probability of settlement. Genetic parentage analyses aligned with larval transport modeling results, indicating self-recruitment of A . triostegus within the bay as well as recruitment into the bay from sites outside. We conclude that Kāne‘ohe Bay retains reef fish larvae and promotes settlement based on concordant results from numerical models, parentage analyses, and field observations. Such interdisciplinary approaches provide details of larval dispersal and recruitment heretofore only partially revealed.
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Key sensitivities for long-distance dispersal models in the North Central Pacific Ocean
Biophysical Lagrangian particle tracking models used to predict larval transport and dispersal are potentially sensitive to input parameters. Here we test the effects of four common input parameters (release interval, number of particles, diffusion, and release depth) for a 2D particle tracking model in the North Central Pacific Ocean. We evaluated the effects on modeled larval transport (particle movement) and dispersal (import) into the Hawaiian Archipelago from eight different regions for a shallow reef organism. Model results were sensitive to all input parameters to varying degrees across the planktonic larval duration/settlement windows and output metrics (transport vs. dispersal) tested. Variation in larval transport pathways 180 days after release was only evident when evaluating depth of release. In contrast, larval transport at 30 days post release did not vary when testing depth of release. Larval dispersal was not different for shorter settlement windows (30 days) regardless of the parameter tested. Occasional connections between distant archipelagos (e.g., Kiritimati, Okinawa, Wake) only occurred when larval duration was at its maximum (180 days), but these long- distance connections were also variable with depth of release. Out of the four parameters tested, changes in release depth resulted in the most significant differences for larval transport and had inconsistent connections for larval dispersal. These outcomes emphasize the importance of choosing a depth layer in future modeling studies. Because factors that affect larval depth distribution, such as spawning depth, buoyancy changes, and swimming behavior, are typically unknown for many taxa, future research should focus on field sampling to determine these in situ behaviors for better parameterization of models.
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- Award ID(s):
- 2049673
- PAR ID:
- 10590081
- Publisher / Repository:
- NOAA Technical Memorandum NMFS-PIFSC
- Date Published:
- Journal Name:
- NOAA Technical Memorandum NMFS-PIFSC
- ISSN:
- 2377-5165
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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