Loss of Coilia nasus habitats in Chinese freshwater lakes: An otolith microchemistry assessment

Abstract

Loss of valued diadromous fishes and their habitats is one of the most critical problems in aquatic habitat connection and resource management worldwide. In China, the Poyang, Dongting, Gaobao, Gucheng, Dongping, and Taihu lakes were known to be historical migratory spawning sites of the anadromous estuarine tapertail anchovy Coilia nasus . However, except for Poyang Lake, it is believed that these lakes are no longer used by anadromous fish owing to overfishing, water pollution, and loss of connectivity. To confirm this assumption, we used an electron probe microanalyzer to analyze elemental strontium (Sr) and calcium (Ca) microchemical patterns in the otoliths of C. nasus individuals sampled from these lakes, in accordance with our previous analysis of the otolithic patterns of the same species sampled from habitat areas characterized by different salinity gradients. The results of line transect analysis of Sr/Ca ratios and Sr X-ray intensity maps of the otoliths indicated that all individuals from Dongting, Gaobao, Gucheng, Taihu, and Dongping lakes were characterized by a freshwater-resident life history. In contrast, individuals from Poyang Lake exhibited both freshwater-resident and anadromous life histories. The findings of this pilot study suggest that anadromous C. nasus can be found in Poyang Lake but are unlikely to be found in Dongting, Gaobao, Gucheng, Dongping, or Taihu lakes, despite these lakes being historical distribution areas or even spawning sites. This anchovy can possibly be used as a good model species for understanding the aforementioned global problem. Given that C. nasus is a commercially important species, restoration of its natural habitats and maintenance of their connections are recommended for its management and conservation.

Evaluation of the Implementation Effect of the Ecological Compensation Policy in the Poyang Lake River Basin Based on Difference-in-Difference Method

“…Poyang Lake and Dongting Lake are the largest watersheds in Jiangxi Province and Hunan Province [40], respectively. Poyang Lake is the largest freshwater lake in China, located in the northern part of Jiangxi Province [41], on the south bank of the middle and lower reaches of the Yangtze River.…”

Genetic Diversity and Population Structure of Coilia nasus Revealed by 2b-RAD Sequencing

“…Among them, the genetic diversity level of the wild population YZ was much lower than that of the other three populations. Considering the geographical features of the river–lake isolation of YZ Lake, it is speculated that the ancestral population of YZ may have been introduced from the Yangtze River through floods or other means [ 38 ]. The subsequent founder effect resulted in an extremely low level of genetic diversity in the YZ population [ 39 ].…”

Temporal stability in the otolith Sr:Ca ratio of the yellow croaker, Larimichthys polyactis (Actinopterygii, Perciformes, Sciaenidae), from the southern Yellow Sea

“…The Mann-Whitney U-test is a non-parametric statistical technique, which is used to analyze differences between the medians of two data sets. This study presents the Mann-Whitney U-test as a statistical technique to examine differences between two independent groups on a continuous scale, namely, the differences in otolith Sr:Ca ratios between high and low phases of each otolith sample as described in previous studies (Yang et al 2006;Liu et al 2015;Jiang et al 2019;Sokta et al 2020). The Mann-Whitney U-test was defined as follows:…”