Growth patterns of specialized reef fishes distributed across the Red Sea to Gulf of Aden

Determining how growth rates and body size vary spatially and among reef fish species is important to understanding functional traits and demographic trade-offs. Variability in reef fish growth trajectories may be influenced by intrinsic (e.g., biological, phylogenetic) and extrinsic factors (e.g., environmental), as well as their interaction via ecological processes. To assess interspecific variation in these traits, we estimated age and growth for a guild of butterflyfishes sampled from reefs spanning ~ 10˚ degrees of latitude in the Red Sea to the adjacent Gulf of Aden. This study region was chosen because it spans environmental gradients known to influence fish life history traits and allowed for comparisons between regional versus more widespread butterflyfish species. Across the 10 study species, we found significant interspecific differences in growth. This finding contrasted with almost no intraspecific differences between populations across the study region. Moreover, we found that maximum body size was significantly correlated with the phylogenetic placement of the butterflyfish species. These patterns suggest that intrinsic factors and a high degree of ecological specialization may elicit spatially conservative demographic profiles, even when faced with considerable environmental variation across a region.