Ageing of juvenile coral grouper (Plectropomus maculatus) reveals year-round spawning and recruitment: implications for seasonal closures

Harrison, H.B., Drane, L., Cresswell, B.J., Evans, R.D., Galbraith, G.F., Srinivasan, M., Taylor, B.M., Williamson, D.H., and Jones, G.P. (2023) Ageing of juvenile coral grouper (Plectropomus maculatus) reveals year-round spawning and recruitment: implications for seasonal closures. Proceedings of the Royal Society of London Series B, Biological Sciences, 290. 20230584.

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Temporal patterns in spawning and juvenile recruitment can have major effects on population size and the demographic structure of coral reef fishes. For harvested species, these patterns are crucial in determining stock size and optimizing management strategies such as seasonal closures. For the commercially important coral grouper (Plectropomus spp.) on the Great Barrier Reef, histological studies indicate peak spawning around the summer new moons. Here we examine the timing of spawning activity for P. maculatus in the southern Great Barrier Reef by deriving age in days for 761 juvenile fish collected between 2007 and 2022, and back-calculating settlement and spawning dates. Age-length relationships were used to estimate spawning and settlement times for a further 1002 juveniles collected over this period. Unexpectedly, our findings indicate year-round spawning activity generates distinct recruitment cohorts that span several weeks to months. Peak spawning varied between years with no clear association with environmental cues, and little to no alignment with existing seasonal fisheries closures around the new moon. Given the variability and uncertainty in peak spawning times, this fishery may benefit from additional and longer seasonal closures, or alternative fisheries management strategies, to maximize the recruitment contribution from periods of greatest reproductive success.

Item ID: 80430
Item Type: Article (Research - C1)
ISSN: 1471-2954
Keywords: Fisheries management, marine conservation, Coral trout, spawning, recruitment
Copyright Information: © 2023 The Authors. Published by the Royal Society under the terms of the Creative Commons Attribution License, which permits unrestricted use, provided the original author and source are credited.
Funders: Australian Research Council (ARC), ARC Centre of Excellence for Coral Reef Studies
Projects and Grants: ARC DP190103056
Date Deposited: 13 Sep 2023 02:38
FoR Codes: 31 BIOLOGICAL SCIENCES > 3103 Ecology > 310305 Marine and estuarine ecology (incl. marine ichthyology) @ 10%
31 BIOLOGICAL SCIENCES > 3103 Ecology > 310307 Population ecology @ 30%
41 ENVIRONMENTAL SCIENCES > 4104 Environmental management > 410401 Conservation and biodiversity @ 60%
SEO Codes: 18 ENVIRONMENTAL MANAGEMENT > 1805 Marine systems and management > 180599 Marine systems and management not elsewhere classified @ 100%
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