Growth strategies across life-history stages and generational turnover of cryptobenthic coral reef fishes of the genus Trimma.

Abstract

Somatic growth influences survival and reproduction, with flow-on effects on population dynamics and energy fluxes within ecosystems. Small-bodied cryptobenthic reef fishes may contribute significantly to productivity due to their life-history traits, including growth rates and rapid generational turnover. However, comprehensive studies on growth that encompass all stages of life are rare. This study aimed to investigate growth patterns across life-history stages and generational turnover rates in three Trimma species that are abundant on coral reefs in the Pacific: Trimma benjamini, Trimma capostriatum and Trimma yanoi. The Trimma species examined exhibited small body sizes of <25 mm and short life spans of <140 days, potentially enabling them to produce over three generations annually. Three growth models were compared (Modified Fry model, Body Proportional Hypothesis, and the Biological Intercept model) to back-calculate growth at ages prior to capture, and the Body Proportional Hypothesis performed the best in each species, indicated by the lowest residual sum of squares and mean squared error of the model. Each species displayed similar growth patterns, with growth rates varying across different life-history stages. Growth was most rapid during the pelagic larval phase, averaging 0.2 mm per day. The size at settlement was small, ranging from 7.6 to 8.4 mm. Growth was initially rapid post-settlement but gradually slowed, averaging 0.16 to 0.17 mm per day during the juvenile stage. In the adult phase, growth was non-asymptotic, averaging approximately 0.15 mm per day, with 31.3%-37.0% of total growth occurring during this stage. Growth decreased by 8.6%-11.7% following maturation, which is minor compared to the patterns observed in larger fish species. These findings support the expanding literature, suggesting cryptobenthic reef fishes exhibit unique life-history traits that could be associated with their small maximum body size.