TAIPEI (Taiwan News) — The Ocean Conservation Administration announced the results of its 2025 monitoring program for Indo-Pacific humpback dolphins along Taiwan’s west coast, identifying four calves with distinguishing features for inclusion in the species registry, per CNA.
The dolphin, also known as the Chinese white dolphin ("Sousa chinensis"), inhabits shallow coastal waters. Its coloration ranges from gray to white and pink.
The species faces threats from habitat loss and is classified as “vulnerable” on the International Union for Conservation of Nature Red List of Threatened Species.
Researchers said the calves demonstrate reproductive progress within the population. The monitoring survey covered a round-trip route from Miaoli County to Tainan, spanning more than 2,500 kilometers and nearly 155 hours of observation.
Scientists noted that dolphins can be identified by their prominent dorsal fins and distinctive markings. This species was once considered a subspecies of the Indian Ocean humpback dolphin, but DNA analysis later confirmed it as a separate species.
By comparing eyewitness reports with marine survey data, researchers identified 30 individual dolphins, including 25 calves, four of which developed distinctive spots and notches during continued observation, leading to identification numbers OCA071 through OCA074.
During the 2025 survey, researchers observed 17 groups of dolphins, including eight groups of mothers accompanied by calves. About 90% of the species migrated across three or more counties or cities, potentially creating environmental pressure across different regions and underscoring the need for coordinated conservation efforts.
To enhance monitoring, the Coast Guard installed two sets of passive underwater recording devices off the coast of Yunlin County to capture echolocation signals from dolphins and other marine life. Officials said acoustic monitoring can supplement visual surveys and provide additional environmental data.
Analysis of the recordings found that dolphin echolocation activity was more detectable at night and occurred more frequently during high tide. Researchers linked this to foraging behavior and fish availability, offering insight into the dolphins’ activity and feeding times.
The Coast Guard said reports from fishermen have expanded monitoring and increased data sources and geographic coverage. By integrating such data, government agencies, regional authorities, and the public can play a more active role in monitoring and habitat management for this vulnerable species.
