Yangtze finless porpoise is experiencing perhaps irreversible decline



by LORENZO CIOTTI

Yangtze finless porpoise is experiencing perhaps irreversible decline

Yangtze finless porpoise lives only in the catchment area of the middle and lower reaches of the river. In addition to the Yangtze, it is present in the Poyang lake and in the river that crosses it, the Gan Jiang, in the Dongting lake and in its largest tributary, the Xiang Jiang.

In the Yangtze the species ranges up to about 1600 km upstream from its estuary, more or less as far as the city of Yichang. It lives only in fresh waters. After the possible disappearance of the lipote and its rapid population decline, the Chinese government has granted the Yangtze fin porpoise the highest level of protection.

However, in 2012 the situation had become so serious, due to the lack of prey, pollution and naval traffic, that scholars estimated a high probability (86.06%) of extinction within the next 100 years. To the aforementioned threats, we must add the damage caused by underwater noise pollution: when the noises in the water exceed the acoustic threshold of the finless porpoises, their possibility of survival is greatly endangered.

Yangtze finless porpoise is experiencing perhaps irreversible decline

Bycatch by unwary fishermen can pose a serious threat to a species that has become as rare as the Yangtze finless porpoise. Illegal fishing using dangerous gear, such as gillnets, is widely practiced in the Yangtze.

The preferred habitat of the finless porpoise largely overlaps areas where gillnets are most numerous, making the species particularly vulnerable to entanglement and subsequent drowning. The increase in naval traffic, pollution and the continuous degradation of the river environment have contributed to the decline of the population.

In addition to being dangerous for specimens that can die as a result of collisions with the propellers, ships are also harmful because the noise they produce can impair the ability of finless porpoises to communicate with their own kind, as well as hinder their biosonar, making it more difficult foraging and locomotion.

The Yangtze finless porpoise population plummeted by 52% between 1991 and 2006, declining at least 6.4% annually during that period. In 2008, scholars estimated a population of 1,100 to 1,200 individuals in the main river, down to just about 500 individuals by the end of 2012, although a few hundred remained in the interconnected lake systems.

Also in 2012, experts from the World Wildlife Fund estimated that the rate of decline was accelerating by 13.7% per year. By 2017, however, the total number had climbed back to 1,012. Thanks to conservation programs, cetaceans have reappeared in places like Nantong, where sightings had become very rare in recent years. In 2021, almost 500 specimens were identified in Poyang Lake alone.