Re ECF Project: 2010-28

Project Title: Assessment survey of non-native marine species in Hong Kong

Applicant: Dr. Clement P. DUMONT of The University of Hong Kong

Total Approved Grant: $500,000

Duration: 1/4/2011 to 31/7/2012

Project Status/Remarks: Completed

The project aims to define the current spatiotemporal distribution of reported non native marine species in Hong Kong and improve public awareness of their threats to the Hong Kong marine communities.

Summary of the Findings/Outcomes:
Among the 31 sites surveyed only four of the target non-native species were recorded, the sessile tunicate Ciona intestinalis, the slipper limpet Crepidula onyx, the mussel Mytilopsis sallei and the mobile isopod Sphaeroma walkery. According to wet and dry season monitoring (field observation, photo-quadrats and destructive quadrats) the distribution of the sessile non-native species did not seem to be affected by the oceanic zones. The assemblages of the main taxa on fouling communities were influenced by the site but not by the oceanic zones. The cryptogenic species Bugula neritina, Hidroides elegans and Styela plicata were common on fouling communities, while sessile non-native species were restricted mainly to Hong Kong Island and Victoria Harbour. Their abundances were very low, except for Victoria Harbour, which was the only site where all the non-native species recorded were present and in high abundances. On the other hand, the isopod S. walkery was a common species of fouling communities at most of the sites, with the highest abundance recorded at the aquaculture site in Tolo Harbour.

The assemblage compositions of main taxa and the abundances of non-native species are apparently related to seawater quality. Kwun Tong was the site with the lowest water quality and also with the highest abundance of non-native species. Further, the abundance of S. walkery was significantly correlated with a decrease of the water quality.

Non-native species did not appear on permanent quadrats during the one-year monitoring period, which suggests that these species are not a common component of the fouling communities. On monthly recruitment panels, only one small individual C. intestinalis appeared on a panel in Joss House Bay. However, few individuals of C. intestinalis were observed inside of exclusion predation cages (preliminary study), which suggest that the presence of C. intestinalis and probably other introduced species on fouling communities, could be restricted by predation.