The authors thank the Director of Agriculture, Fisheries and Conservation for permission to publish this paper, Keith Kei, Alfred Au, Yiu-ming Mak, Peter Yip, King-tai Wo, Homer Chau, Lawrence Leung and Pak-ki Wong for their assistance in the surveys, Kin-Fung Fong for analyzing the photoquadrats, and Yanan Sun for preparing some of the figures.