Abstract:

Aims: The Yarlung Tsangpo River, one of the ten longest rivers in China, spans two major zoogeographic regions of the world: The Palearctic and the Oriental realms. While previous papers have focused on small portions of the river, a basin-wide-scale study to catalog its fish composition, diversity patterns, and species fluctuation is lacking. This study synthesized empirical data from field studies over the past two decades on fish diversity in the Yarlung Tsangpo River, compiled a list of fish diversity in the Yarlung Tsangpo River Basin in China, and analyzed the status of the fish diversity and the main threats to its diversity. The findings provide a scientific foundation for management and conservation of fish diversity in the Yarlung Tsangpo River Basin.

Methods: In total, 66 sections were included in this study. Of them, 58 were actually surveyed in the field, and 8 were collected from literatures; two in the upper reaches, 40 in the middle reaches, and 24 in the lower reaches; 24 in the main stream, 33 in the tributaries, 2 in the lakes, 3 in the tributary reservoirs, and 4 wetlands. These sampling sections (locations) were selected according to their geomorphological characteristics, as well as the accessibility of each location for sampling. The fish investgations were conducted from 2004 to 2023. Methods for collecting fishes included gillnets, shrimp coops, and battery-powered backpack electrofisher. After compiling the data from all of the sites, the degree of endemicity was calculated using the corrected weighted endemism index.

Results: There are 155 native species in 10 orders, 25 families, and 70 genera in the Yarlung Tsangpo River Basin. Out of all of the detected species, 29 species and one genus are endemic to the river. Five species were on China’s Key Protected Species List (Grade II); and 26 species were categorised as threatened (i.e. endangered, vulnerable, or near threatened) on the IUCN Red List of Threatened Species and China’s Biodiversity Red List. The sections with high species richness are located in the middle and lower reaches of the Yarlung Tsangpo River, while the lowest species richness is found in the Great Canyon sections. Fish fauna of the river is dominated by Qinghai-Tibetan Plateau, and South Asian fishes. The Jiaresa-Bangxin section of the Yarlung Tsangpo River Grand Canyon may be the boundary between the two major zoogeographical regions of freshwater fish. By the end of 2023, 30 species of non-native fish in 8 orders, 16 families, and 24 genera had been recorded in the natural water bodies of the Yarlung Tsangpo River Basin. Of these non-native fish species, three species were introduced to different regions within the Yarlung Tsangpo River Basin. In recent years, there has been a rapid increase in the introduction of both native fishes and non-native cold-adapted fishes through the plateau’s drainage systems.

Conclusion: Through cataloging the fish diversity in the Yarlung Tsangpo River Basin, we found that invasion of non-native fishes is the main threat to fish diversity. In the future, we should focus on fish surveys of lakes and tributaries in the lower reaches of the river, strengthen the resources for data integration, and establish a basin-level data management platform. Further, taxonomic research should be strengthened through international cooperation. Additionally, long-term monitoring of fish resources should be implemented as soon as possible to monitor fish diversity and promote conservation in the Yarlung Tsangpo River.

Key words: non-native fishes, dam, taxonomy, biodiversity, fauna, threat factors