Motu Analysis of Ichthyoplankton Biodiversity in the Upper Yangtze River, China

Abstract: The difficulty in species identification can be a major hindrance in conducting ichthyoplankton surveys for fish biodiversity investigations. Here, we evaluate the feasibility of a molecular operational taxonomic unit (MOTU) approach for ichthyoplankton investigations, and describe fish biodiversity in the Jinshajiang section of the upper Yangtze River, China. The MOTUs were established by grouping specimens diverging less than 1.00% Kimura two-parameter (K2P) distance units from their nearest neighbor within the same MOTU. Taxonomic assignment of the MOTUs was performed by comparing the MOTU sequences with COI sequences of taxonomic species. Sixty-eight MOTUs were inferred from 818 COI sequences of ichthyoplankton in the Jinshajiang section. Among those, one MOTU was composed of two identified taxonomic species, and each of the other MOTUs was linked to a single identified taxonomic species. Just 26 MOTUs were successfully identified to taxonomic species due to the limited reference database. Our results demonstrate that the MOTU approach can be applied successfully for analyzing biodiversity and identifying species of freshwater ichthyoplankton. Richness of ichthyoplankton revealed in this study was much higher than previous ichthyoplankton surveys in this section. Our results suggests that the Jinshajiang section should be an important target for fish biodiversity conservation in the Yangtze River.