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

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 optimising 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 1,002 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..., Harrison HB, Drane L, Berumen ML, Cresswell BJ, Evans RD, Galbraith GF, Srinivasan M, Taylor BM, Williamson DH, Jones GP. 2023 Ageing of juvenile coral grouper (Plectropomus maculatus) reveals year-round spawning and recruitment: implications for seasonal closures. Proc Roy Soc B.
Otolith preparation and age determination
The sagittal otoliths were extracted from a subset of individuals from each collection period (Table S1) to estimate age and age-length relationships of juvenile P. maculatus. The preparation of otoliths followed the methods described in (Taylor et al 2016) and is consistent with previous studies of early life history growth in P. maculatus from the southern GBR (Mannering et al. 2008; Harrison et al. 2012, 2020; Williamson et al. 2016). Briefly, one otolith from each juvenile fish was affixed to a glass microscope slide using thermoplastic glue (Crystalbond 509), with the primordium (nucleus) on the inside edge of the slide and sulcus ridge perpendicular to the slide ..., Please see the README document (\"README.md\") and the accompanying published article: Harrison HB, Drane L, Berumen ML, Cresswell BJ, Evans RD, Galbraith GF, Srinivasan M, Taylor BM, Williamson DH, Jones GP. 2023 Data from Ageing of juvenile coral grouper (Plectropomus maculatus) reveals year-round spawning and recruitment: implications for seasonal closures. Proc Roy Soc B, Accepted DOI: https://doi.org/10.1098/rspb.2023.0584,