Juvenile fish communities in coastal soft-bottom and shallow water habitats at the Tolo Harbour and Channel in Hong Kong, South China

Coastal soft-bottom and shallow water habitats are often key nursery grounds for marine fishes, which are important not only in supporting a rich biodiversity, but also of social-economic importance in terms of ecosystem services and fishery resources provided by these habitats. Tolo Harbour and Channel (the Tolo Area) at north-eastern Hong Kong in South China has been previously recognised as a nursery ground of marine fish species, including those that are commercially important. However, marine biodiversity and fisheries resources in this area have been jeopardized by various anthropogenic threats such as coastal development and pollution. This study aimed at providing up-to-date ecological information of juvenile marine fishes in the Tolo Area, and identifying locations with a high conservation priority. A three-year study, using beach and purse seining, was carried out to assess the current status of the juvenile fish community in coastal soft-bottom and shallow water habitats throughout the Tolo Area. A total of 171 species/taxa were recorded, including the IUCN-red-listed vulnerable species of seahorse Hippocampus kuda. Juvenile individuals were found in 155 of the recorded species/taxa. Juvenile fishes were dominated by small and/or fast-growing species. Significant spatial and seasonal variations in juvenile fish assemblages were recorded in the Tolo Area. Diel differences in juvenile fish assemblages were also recorded in sites where additional night-time surveys were conducted. Species richness was generally higher in outer Tolo Harbour and inner Tolo Channel, and priority should be given to the coastal soft-bottom and shallow water habitats in these areas to protect the species diversity and fishery resources. The results of this systematic study provide an ecological baseline of juvenile fishes in the Tolo Area for future monitoring and conservation of the marine fish communities. •171 species/taxa were recorded by beach seining and purse seining in the Tolo Area.•Juveniles were recorded in 155 species/taxa, including commercially important species.•Juvenile fish communities in nearshore soft-bottom and shallow water habitats showed spatial and temporal patterns.•Juveniles of Hippocampus kuda, an IUCN-red-listed vulnerable species of seahorse, were recorded in the Tolo Area.•Priority areas for conservation of nearshore soft-bottom and shallow water habitats were identified.