Mismatch between shape changes, early growth, and condition for a temperate reef fish from an oceanic island

Abstract

Settlement is a key process in the life history of marine fish, when shape and ecological changes occur during the transition from a pelagic larva to a benthic juvenile. We studied the covariation of shape changes, condition, and pre- and post-settlement growth of settlers (17–30 mm) of the wrasse, Pseudolabrus gayi, from the Robinson Crusoe island, south-eastern Pacific. Specimens were collected during late March 2018 from four locations at 20 m depth and from a large, natural intertidal pool. The morphospace and the allometry were characterised by landmark-based geometric morphometrics, size and growth were estimated using sagittae otolith microstructure analysis, and condition was determined using the Fulton index. The settler’s phenotype varied from a robust shape with ventrally oriented mouth opening, to slender specimens with frontally oriented mouth, with similar body morphospace among sites. The mean pelagic larval duration was 44.8 ± 4.6 days, settling at 19 ± 2 mm SL. The mean post-settlement growth rate was low (0.09 mm day−1), showing low static allometry (3%). Differences among locations occurred in terms of settler’s condition and growth prior and after settlement, suggesting effects of the microhabitat and potential predators. Therefore, the variability in the settler’s morphospace was decoupled of pre- and post-settlement growth and condition during the transition from pelagic to benthic habitat. Finally, this study highlights the dynamic nature of the settlement–transition period for a temperate reef fish in a period when phenotype variations in body shape and early life-history traits vary asynchronously.