Tidal migrations of juvenile Sillago spp. in a subtropical intertidal nursery seascape

Abstract

Context: Subtropical intertidal pools on depositional shores are important nursery habitats for smaller juveniles (10 to 25-mm total length, TL) of commercially important smelt whiting (Sillago spp.), whereas larger juveniles >25 mm TL occupy shallow subtidal habitats at low tide. Aims: We investigated the connectivity between lower and upper shore habitats in Moreton Bay. Methods: We used funnel camera traps to assess tidal movements of juvenile whiting and compared harpacticoid copepod genera in small juvenile whiting guts caught post-foraging with those sampled from nearby sediments to infer patterns of foraging. Key results: Smaller juveniles transited sandy upper-shore habitat at depths from 1.5 to <10 cm and avoided vegetated habitats, whereas larger juveniles moved into mangroves at depths of 15-30 cm on the rising tide. Coullana spp. harpacticoids were found in greater proportions in whiting guts of small juveniles than in the sampled habitats, but were abundant in intertidal pool and mangrove sediments. Conclusions: Intertidal sandy habitats are seemingly an important high-tide habitat for smaller juvenile whiting, where they preferentially forage on Coullana spp. Implications: Given the broad distribution of smelt whiting in the Indo-Pacific, the protection of such habitats must be addressed by fishery and habitat management agencies for species with similar early nursery requirements.