Interdisciplinary analysis of larval dispersal for a coral reef fish: opening the black box

Cww Counsell,Ma Mcmanus,Mj Donahue,Ss Lal,Bw Bowen,Ab Neuheimer,Rr Coleman,Rj Toonen,Ec Franklin,Ma Hixon,Bs Powell

doi:10.3354/meps13971

Abstract

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.

Highlights

Many coastal fish species have complex life cycles wherein reef-associated adults produce pelagic larvae that are dispersed by oceanographic processes (Leis & McCormick 2002) before returning to near-Publisher: Inter-Research · www.int-res.comMar Ecol Prog Ser 684: 117–132, 2022 and connectivity between local populations are governed by the interplay of oceanographic dynamics, geographic features, larval behavior, and life history traits that influence patterns of larval dispersal (e.g. Hjort 1914, Caley et al 1996, Schweigert et al 2010, Peck et al 2012)
Depending on the species and environment, larval dispersal distances range anywhere from self-recruitment back to the same reef where spawned (Schultz & Cowen 1994, Taylor & Hellberg 2003, Jones et al 2005, Cowen et al 2006, Gerlach et al 2007, Almany et al 2017) to 100s of km (Kinlan & Gaines 2003, Christie et al 2010), with combinations of patterns observed (Williamson et al 2016, Johnson et al 2018). Some of this variation in distance traveled is a result of temporal variability in the pelagic larval stage (Selkoe & Toonen 2011), with pelagic larval duration (PLD) ranging from 7−94 d across reef fish species and intraspecific variability in PLD ranging from 3−56 d (Green et al 2015)
Larvae released in regions outside of Kāne‘ohe Bay had lower probabilities of settlement than larvae released in regions inside the bay: North Coast (2%), Mid Coast (6%), Mokapu (11%), and South Coast (1%)

Summary

Introduction

Many coastal fish species have complex life cycles wherein reef-associated adults produce pelagic larvae that are dispersed by oceanographic processes (Leis & McCormick 2002) before returning to near-Publisher: Inter-Research · www.int-res.comMar Ecol Prog Ser 684: 117–132, 2022 and connectivity between local populations are governed by the interplay of oceanographic dynamics, geographic features, larval behavior, and life history traits that influence patterns of larval dispersal (e.g. Hjort 1914, Caley et al 1996, Schweigert et al 2010, Peck et al 2012). Depending on the species and environment, larval dispersal distances range anywhere from self-recruitment back to the same reef where spawned (Schultz & Cowen 1994, Taylor & Hellberg 2003, Jones et al 2005, Cowen et al 2006, Gerlach et al 2007, Almany et al 2017) to 100s of km (Kinlan & Gaines 2003, Christie et al 2010), with combinations of patterns observed (Williamson et al 2016, Johnson et al 2018). Larval movement has long been regarded as one of the great ‘black boxes’ in marine ecology (Caley et al 1996, Grosberg & Levitan 1992), yet multidisciplinary approaches hold great promise for illuminating this enigmatic part of the marine life cycle (Petitgas et al 2012, Williamson et al 2016, Johnson et al 2018, Hixon et al 2022)

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Conclusion