Population and Conservation Status of Iirawaddy Dolphins (Orcaella brevirostris) in Trat Bay, Trat Province, Thailand

Abstract

Trat Bay is an important area for fishing activities along the Eastern coast of the Gulf of Thailand. The Irrawaddy dolphin (Orcaella brevirostris) is the dominant species in this area. They are currently listed as an endangered species in Thailand. The distribution and behavior of Irrawaddy dolphins in Trat Bay, were investigated between 2010-2012. The photo identification technique was used to estimate density of Irrawaddy dolphins. We also conducted interviews with small-scale fishers, and collected information on dolphin stranding. Photo identification results indicated that Irrawaddy dolphins inhabit the coast of Trat Province all year round and could be observed with calves mainly between December and February. Group sizes observed ranged from 5 to 20 individuals. The minimum population was estimated as 171±73.18 individuals. Many dolphins were observed around fishing boats, area closed by used fishing gears and artificial reefs. As the results of fishing gear mapping, the most common fishing gears used by the fishery communities in Trat Bay are gill nets and crab traps (54% and 25% respectively), especially during the spring tide. Five Irrawaddy dolphins were found entangled in fishing gears during this research. The high density of fishing gears is likely the major threat to dolphins in this area. These obtained data could contribute to management and strategies for dolphin conservation based on integration of local community agreement.