Averting the baiji syndrome: conserving habitat for critically endangered dolphins in Eastern Taiwan Strait

1.Numbering no more than 100 individuals and facing many threats, the geographically isolated Eastern Taiwan Strait population of Indo-Pacific humpback dolphins (Sousa chinensis) is in peril. The estuarine and coastal waters of central-western Taiwan have historically provided prime habitat for these dolphins, but environmental conditions today bear little resemblance to what they were in the past.2.The humpback dolphins must share their habitat with thousands of fishing vessels and numerous factories built upon thousands of hectares of reclaimed land.3.They are exposed to chemicals and sewage released from adjacent terrestrial activities. Noise and disturbance associated with construction, vessel traffic and military activities are features of everyday life for these animals.4.Measures to slow the pace of habitat deterioration and reduce the many risks to the dolphins are urgently needed. As one practical step in this direction, this paper describes the habitat needs of these small cetaceans so that decision makers will be better equipped to define 'priority habitat' and implement much needed protection measures under the terms of local legislation.5.The preferred habitat of these dolphins in Taiwan consists of shallow (<30 m), near-shore marine waters with regular freshwater inputs.6.For such a small, isolated and threatened population, 'priority habitat' should not be limited to areas of particularly intensive dolphin use or high dolphin density, but rather it should encompass the entire area where the animals have been observed (their current 'habitat'), as well as additional coastal areas with similar bio-physical features ('suitable habitat'). Such a precautionary approach is warranted because the loss of only a few individuals could have serious population-level consequences.7.While conventional socio-economic analysis might suggest that implementing protection measures over an area stretching ~350 km north-south along Taiwan's west coast and ~3 km out to sea would be too 'costly', the loss of this charismatic species from Taiwan's waters would send a troubling message regarding our collective ability to reconcile human activities with environmental sustainability.