Environmental DNA assessment of fish diversity, distribution and niche characteristics in Zhutuo spawning ground in the upper reaches of the Yangtze River

Abstract

[Objective] Implementation of the Ten-Year Fishing Ban policy may alter fish diversity and niche characteristics of dominant species in spawning grounds within the National Nature Reserve for Rare and Endemic Fish in the Upper Yangtze River. This study initiated continuous monitoring of natural spawning habitats from February 2022 to assess these ecological changes. [Methods] Environmental DNA(e DNA) metabarcoding was employed to analyze fish species composition, biodiversity patterns, and niche parameters of dominant species. Water sampling followed the CEN/TS 19461 standard across five monitoring transects(ZT1-ZT5). [Results] The e DNA analysis detected 45 species of fish belonging to 38 genera, 13 families, and 3 orders were detected through environmental DNA(e DNA) in this survey, including 10 species endemic to the upper reaches of the Yangtze River, such as Procypris rabaudi and Myxocyprinus asiaticus. The fish community was mainly composed of bottom-dwelling, settling ovum-producing, omnivorous fish. The variation ranges of the Chao1 index, ACE index, Shannon index, and Simpson index are 736~996, 719~ 965, 1. 58 ~ 3. 23, and 0. 83 ~ 0. 99, respectively, indicating that fish species in spawning sites are abundant and community distribution uniformity is high. All indexes are highest at ZT1 monitoring points. Cluster analysis showed that, at a certain similarity level, fish community types in spawning sites could be basically divided into two groups: ZT1, ZT3, and ZT5 clustered together, and ZT2 and ZT4 clustered together, indicating similar fish community habitats. There are 9 dominant fish species in typical deep pool habitats in the reserve, with niche widths(Bi) ranging from 1. 13 to 3. 87. The dominant fish species are broad and medium niche fish, such as Cyprinus carpio and Hemiculter tchangi, with the niche overlap index(Oik) of some dominant fish species reaching more than 0. 95. This indicates fierce competition for resources among the fish in this spawning ground. [Conclusion] The Zhutuo spawning ground demonstrates high species richness with homogeneous community structure and intense resource competition. This study establishes an e DNA-based monitoring framework that enhances conventional survey method, providing critical baseline data for adaptive management under the fishing moratorium regime.

Keywords

eDNA metabarcoding / fishes endemic to the upper reaches of the Yangtze River / spawning ground / fish diversity / niche characteristics

Funding

National Natural Science Foundation of China(42007213)

Scientific and Technological Research Program of Chongqing Municipal Education Commission(KJQN202000749)

Sponsored by Natural Science Foundation of Chongqing, China(cstc2021jcyjjqX0009)

Joint Training Base Construction Project for Graduate Students in Chongqing(JDLHPYJD2019001)