The Population Sizes of Indo-Pacific Humpback Dolphins (Sousa chinensis) Around Sukon and Sarai Islands, Thailand Estimated Using Photo-Identification Technique

Abstract

The population sizes of Indo-Pacific humpback dolphins (Sousa chinensis) around Sukon Island, Trang Province and Sarai Island, Satun Province on the Andaman coast of Thailand, were estimated using photo-identification technique. The field survey was conducted during November, 2010 – December, 2011. The survey effort at Sukon Island amounted to 11 days, totaling 59.09 hours of observation, while at Sarai Island the survey effort amounted to 15 days and totaled 57.11 hours. A total of 23 dolphins were identified at Sukon Island and a further 24 identified at Sarai Island via photoidentification. Estimation of dolphin population sizes with the Chapman- modified Peterson's mark and recapture model, showed that there were 56±21.5 and 29±4.2 individuals around Sukon and Sarai Islands respectively. Combining the results of photo-identification from the previous and present surveys, the total number of animals was found to be very similar to the estimated population's size predicted using Chapman's equation.