NANJING -- East China's Jiangsu province saw a steep rise last year in fish varieties in the local section of the Yangtze River, the latest survey and monitoring data on biodiversity of the river section showed Saturday.

The data, jointly released by the provincial environmental monitoring center and Nanjing University showed that compared with the total 70 varieties of fish recorded in 2018, Jiangsu registered 81 fish varieties in 2020 along the waterway, an increase of about 15.7 percent, suggesting an improving ecological environment in the waters.

Statistics have shown that the initial fish varieties in the Jiangsu section of the Yangtze River, China's longest waterway, reached 161 based on previous historical records. However, the number tapered off over the years to 108 between 2001 and 2006 as a result of the overexploitation of the river resources.

In 2018, mere 70 fish varieties were spotted in the provincial section of the Yangtze River, with an inordinate number of the low age groups and small fish. Several endangered species in the Yangtze River also dwindled away, as only three out of the province's total 28 monitoring sites spotted the river's iconic finless porpoise.

Starting from July 2020, Jiangsu imposed a fishing ban along the mainstream of the Yangtze River. In 2020, eight out of the 28 monitoring sites reported the appearance of the Yangtze River finless porpoise. The species is the only freshwater subspecies of the finless porpoise family, which can only be found in the middle and lower main streams of the Yangtze River.

In the meanwhile, the province also spotted Huso dauricus, also known as Kaluga sturgeon, a critically endangered species listed on the International Union for Conservation of Nature Red List of Threatened Species in 2010.

Stretching over 6,300 km, the Yangtze boasts rich biodiversity and mineral and water resources in its basin. But overfishing and pollution have long threatened its aquatic life and depleted its fish stocks. China has launched a complete 10-year fishing ban in the key waters of the Yangtze since the beginning of 2021.