Shallow patch reefs as alternative habitats for early juveniles of some mangrove/seagrass-associated fish species in Bermuda

Abstract

Various coral reef fish species are highly associated with putative nursery habitats like mangroves and seagrass beds during their juvenile life stage (i.e., 'nursery species'). Little is known, however, of the degree to which they can use other habitat types as juvenile habitat. In this study we investigated whether some nursery species can utilise alternative juvenile habitats when mangroves and seagrass habitats are not readily available. Visual census surveys were carried out in six different coastal habitat types on the Western Atlantic island of Bermuda, and densities of early juveniles (<4 cm) were quantified for four nursery species and compared to that of four non-nursery species. Early juveniles of the nursery species Haemulon flavolineatum and Scarus iserti were observed in a variety of habitat types, consisting of their common juvenile habitats (mangroves, seagrass beds and undercut notches in large boulders) as well as of non-typical juvenile habitats (shelf patch reefs). Two other nursery species, Haenudon schirus and Lityanus griseus, were only present in the mangroves, seagrass and boulder habitats. All non-nursery species were only observed on the shelf patch reefs. Our findings suggest that some nursery species are flexible in their choice of early juvenile habitat, while other nursery species are more dependent on mangroves and seagrass beds even when these habitats are locally scarce.