Humpback dolphins in Hong Kong and the Pearl River Delta: Status, threats, and conservation challenges

Abstract

In coastal waters of the Pearl River Delta (PRD) region, the Indo-Pacific humpback dolphin (Sousa chinensis) is thought to number approximately 2,500 individuals. Given these figures, the putative PRD population may appear strong enough to resist demographic stochasticity and environmental pressures. However, living in close proximity of the world’s busiest seaport/airport and several densely populated urban centres with major costal 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 is given any form of protection. All current MPAs 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 restructuring of the fundamental approach to conservation management is urgently needed.