Humpback Dolphins in Hong Kong and the Pearl River Delta: Status, Threats and Conservation Challenges.

In coastal waters of the Pearl River Delta (PRD) region, the Indo-Pacific humpback dolphin (Sousa chinensis) is thought to number approximately 2500 individuals. Given these figures, the putative PRD population may appear strong enough to resist demographic stochasticity and environmental pressures. However, living in close proximity to the world's busiest seaport/airport and several densely populated urban centres with major coastal infrastructural developments comes with challenges to the long-term survival of these animals. There are few other small cetacean populations that face the range and intensity of human-induced pressures as those present in the PRD and current protection measures are severely inadequate. Recent mark-recapture analyses of the animals in Hong Kong waters indicate that in the past two decades the population parameters have not been well understood, and spatial analyses show that only a very small proportion of the dolphins' key habitats are given any form of protection. All current marine protected areas within the PRD fail to meet a minimum habitat requirement that could facilitate the population's long-term persistence. Demographic models indicate a continuous decline of 2.5% per annum, a rate at which the population is likely to drop below the demographic threshold within two generations and lose 74% of the current numbers within the lifespan of three generations. In Hong Kong, the case of humpback dolphins represents a particularly explicit example of inadequate management where a complete revision of the fundamental approach to conservation management is urgently needed.

Identification of stomatopod larvae (Crustacea: Stomatopoda) from Hong Kong waters using DNA barcodes.

The Stomatopoda (Crustacea: Malacostraca) from the South China Sea region are of commercial importance and although limited studies have been conducted on the adults, no research has ever been attempted on the larval stages because of the lack of identification keys or taxonomic descriptions. In the first study of its kind in the region, DNA barcoding was used successfully to identify unknown stomatopod larvae from plankton samples. Sequences of two mitochondrial genes, namely the cytochrome c oxidase subunit-I (COI) and the large ribosomal subunit (16S) rRNA, were applied as the barcodes to match DNA sequences from unknown larval morphotypes against those of known, locally occurring adult species. Intraspecific variations for the COI and 16S rRNA genes were found to be <2.4% and <2.1% respectively in terms of Kimura 2-Parameter (K2P) divergence of the adults, whereas variations between genera ranged from 13% to 24% and 3% to 11% respectively. These results imply that both genes are suitable for use in species identification of stomatopods; thus 14 of the 16 larval morphotypes (87.5%) obtained in Hong Kong waters can be identified to seven species through DNA barcoding. The findings of this study would also facilitate future research on the larval ecology and phylogenetic relationship of these crustaceans.