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The Qiantang River dolphin?

By on June 6, 2007 in Uncategorized, EDGE Updates, Focal species, Yangtze river dolphin

The Qiantang River is a large river in eastern China that travels through Jiangxi and Zhejiang provinces. Although several hundred miles south of the Yangtze, the Qiantang also contained a population of Yangtze River dolphins or baiji (Lipotes vexillifer) well into the twentieth century. It is not as big as the Yangtze, but is still a large river: it has a total length of 484 km, a drainage basin of 42,000 km2, and an average annual flow of 40.4 billion m3. In the areas where baiji were found, the width of the river was between 500 and 1200 metres. Since the river is situated in a similar climate zone to the Yangtze, it is not surprising that it was able to support baiji, although how they got there in the first place is open to speculation.

Qiantang River

Very little information is available about the former occurrence of baiji in the Qiantang River. During a flood in the 1950s there were reports of seeing about ten baiji in the river between the towns of Tonglu and Fuyang, about 320 kilometres from the river mouth. One of these individuals was killed and collected, and is now on display at the Zhejiang Natural History Museum in Hangzhou – a picture of this specimen can be seen here. This report strongly suggests that these baiji were not just animals occasionally straying from the main population in the Yangtze, but instead represented a resident population. It is not clear what the total baiji population was in the river. However, given that marine biology in China was in its infancy in the 1950s and that no scientific research was carried out during the 1960s because of the Cultural Revolution, the fact that at least ten individuals were reported strongly suggests that there were many more in the river at that time.

Yangtze River dolphin or baiji

Nobody knows exactly why baiji are no longer seen in the Qiantang River. Human impacts along the river are very similar to those in the Yangtze, and the reasons for the disappearance of the species are probably the same in both rivers: destructive fishing practices, dam construction and boat traffic. Of these factors, dam construction is often considered to be the most likely reason, as a large dam was built at Xinanjiang on the Qiantang in the late 1950s, and this coincides with the end of reported sightings of baiji in the river. However, none of these theories have been thoroughly studied, and remain very speculative. It is still (remotely) possible that there are still some baiji hiding out in some remote bend of the Qiantang, as the river has not been surveyed for cetaceans for many years.

Boat on the Qiantang River

How did baiji originally get into the Qiantang River? It is possible that they could have migrated from the Yangtze to the Qiantang when the mouths of the two rivers were closer to each other than they are today. During recorded history, both river mouths have changed location drastically due to the build-up of silt. It is not hard to imagine that in the 20 million year history of the baiji, at one point the two mouths were located close enough for them to easily migrate from one river to the other. However, it is also possible that the Qiantang may have been originally connected to the Yangtze.

The Qiantang River apparently still contains finless porpoises, which are occasionally seen in the river. The last time they were seen as far upstream as Tonglu was in the 1990s, though they are often seen by the river mouth in Hangzhou. However these finless porpoise are not the same subspecies as the one endemic to the Yangtze (Neophocaena phocaenoides asiaeorientalis), but instead represent the subspecies found along the eastern coast of China and in the Sea of Japan (Neophocaena phocaenoides sunameri). The fate of the Qiantang River’s finless porpoises remains uncertain, and continued development and industrialization along the river may mean that they will share the same fate as the river’s former population of baiji.

Alf Hickey