Juvenile Fish Assemblages in Mangrove and Non-Mangrove Soft-Shore Habitats in Eastern Hong Kong

Conducted in subtropical coastal waters of eastern Hong Kong, this study provides information on species compositions of juvenile fish communities in several mangrove and non-mangrove habitats, and evaluated the influences of water temperature, salinity, turbidity, sediment organic matter (SOM), water depth, and sediment grain size on fish assemblages. In total, 85,427 fish belonging to 76 species from more than 29 families were collected. Fish densities were higher in mangrove mudflats than in non-mangrove habitats, but only a few of the dominant species were significantly more abundant in mangrove than in non-mangrove habitats. Fish assemblages in mangrove and non-mangrove mudflats were quite similar. Fish compositions were influenced by environmental factors including the SOM and water depth, but not by the presence of mangroves. The present study suggests that the nursery function of mangroves is both site- and species-specific. Compared to shallow mudflats with and without mangroves, deep-water sandy beaches may be less suitable for juvenile fish because of their low SOM content and high piscivorous fish abundances. More studies need to be conducted before definitive conclusions can be made on the nursery function of mangroves in Hong Kong and subtropical Asia.