First population assessment of the Asian Water Dragon (Physignathus cocincinus Cuvier, 1829) in Thua Thien Hue Province, Vietnam

Abstract

The Asian Water Dragon, Physignathus cocincinus Cuvier, 1829, was originally described from southern Vietnam. Wild populations of this species are strongly affected by harvesting, particularly in central Vietnam, while potential negative impacts are not yet foreseeable. This study provides the first population size estimation using a capture-recapture approach and an evaluation of threats to and trade levels in P. cocincinus in Thua Thien Hue Province, central Vietnam. Field surveys were conducted at 14 sites of known occurrences of the species in Thua Thien Hue during April and June of 2016 and 2017. The estimated population size of the species amongst these sites ranged from 232 to 250 individuals. The mean abundance varied from 1.98–2.64 individuals/100 m along inhabited streams. This study revealed harvest activities for local food consumption and to supply the pet trade. Accordingly, imports of several thousand living individuals per year from Vietnam into the EU were documented. It was further demonstrated that the level of negative impacts on different sub-populations is in accordance with respective abundances and the incidence of adults. This finding indicates that rising harvest levels in concert with decreasing habitat quality, might seriously affect the wild population of P. cocincinus in the future. Thus, the authors herein emphasise the necessity for increased conservation measures and for monitoring of the species as well as its natural habitat in order to warrant a sustainable use of the species in the future.