Chinese researchers have revealed that one of the world's oldest unchanged aquatic species is at risk of extinction as pollution in the Yangtze River has affected the fish's reproduction cycle.

The Chinese sturgeon is part of a family of fishes that scientists say may have been in existence up to 200 million years ago. The adaptability of this animal has enabled it survive several changes in its habitat throughout this period.

However, the Chinese Academy of Fisheries Sciences has revealed that due to overly high pollution levels in the Yangtze River, sturgeons were unable to reproduce naturally last year. Researchers from the academy say neither sturgeon eggs nor hatchlings were discovered in the river last year.

Many species of sturgeon, including the Chinese sturgeon, are classed as critically endangered by the International Union for the Protection of Nature and Natural Resources. The scale-less fish takes a long time to reach maturity and does not reproduce at a rapid rate. Reports indicate that the population of Chinese sturgeons has gradually dwindled to just 100 in the world today. Although up to nine million young sturgeons were introduced into the Yangtze River between 1983 and 2007, experts say thousands of these bony fishes have also been killed as a result of illegal fishing practices.

The revelation of the Chinese fisheries sciences academy has sparked many criticisms of the increasing pollution of water bodies in the country. Conservationists say the damming of rivers, overfishing and poaching have also contributed to the depletion of the population of aquatic animals in the country.

The population of many other aquatic animals, including dolphins and crocodiles, has allegedly also plummeted over the past decade. Pundits say the destruction of the habitat of some of these animals is one of the negative consequences of the country's rapid economic expansion.