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Otolith microchemistry allows reconstructing the life histories and understanding the habitat uses of fishes. In this study, the relationship of Sr:Ca ratios and salinity from various environments, i.e. freshwater of the Min River, brackish water of the estuary and seawater of the coastal marine (Fujian Province, China), were built, revealing a significant positive correlation (p < 0.05). A total of 29 adult Chinese gizzard shad Clupanodon thrissa were collected in 2017–2020 for otolith (sagitta) microchemistry. The specimens were only collected from the Min River and the estuary, with none from the coastal marine regions despite same efforts input. The results confirmed that all 29 individuals hatched in either freshwater or brackish water. Four contingents were recognized based on various life histories, including three migratory contingents (Types A-C, N = 26) and one freshwater residential contingent (Type D, N = 3). The three migratory contingents were the freshwater-brackish migratory contingent (Type A, N = 12), the brackish-freshwater migratory contingent (Type B, N = 10) and the brackish-variable migratory contingent (Type C, N = 4). Only a small proportion of C. thrissa individuals (N = 4) migrated to seawater habitat during the first few months of lifetime, and most individuals preferred freshwater habitat during the first year. There were no significant differences between life history pattern and sex (p = 1.00), and between the number of fish migratory times crossing different habitats and age (p = 0.84). The lower reaches of the Min River and the estuary are confirmed to be important spawning grounds for C. thrissa , based on otolith microchemistry of this study and gonad histology of a previous examination. The findings have significant implications for the Min River and the estuary protection and fishery stock management. [ABSTRACT FROM AUTHOR]

Coilia ectenes is a commercially important fishery species. In this study, genetic diversity and population structure of C. ectenes were examined by using mitochondrial DNA control region sequences in 246 individuals sampled from 10 localities in China. One hundred and ninety-five polymorphic sites defined 184 distinct haplotypes, revealing a moderately high haplotype diversity (Hd) and a relatively low nucleotide diversity (π) in the 10 localities. An excess of unique haplotypes at most sample locations were detected, which might influence the genetic structure of the C. ectenes populations. Hd ranged from 0.939 to 1.000 and π ranged from 0.26% to 1.15%. The Dongting fish population had the highest π level. The genetic distances ranged from 0.26% to 1.03% within populations and from 0.56% to 4.90% between populations. The distances between the Fuzhou (FZ) population and other populations were mostly >4.8%. Neighbor-joining tree indicated distinct patterns of phylogeographic structure among haplotypes from FZ population and those from other populations. Analyses of molecular variance and Fst statistics suggested that the divergence existed among populations from 10 localities, indicating that gene flow might be restricted among those regions, despite the wide dispersal. In addition, neutral tests and analysis of mismatch distribution suggested that C. ectenes might have undergone a population expansion. Our study revealed the extant population genetic diversity and structure of the C. ectenes, and was in favor of the related fishery management issues including fishery stock identification and conservation. [ABSTRACT FROM AUTHOR]

Coilia nasus is widely distributed in the Yangtze River, the coastal waters of China, Korea and the Ariake Sound of Japan. Several ecotypes exist and this provides a useful model for the study of comparative diversity between molecular markers. Here we analyze and compare the nucleotide sequences between single-copy ribosomal protein S7 gene intron 1 (rpS7) and multiple-copy ribosomal internal transcribed spacer 1 (ITS1) in this species to compare the phylogenetic signal of the two nuclear genes. Nucleotide substitutions among the two gene sequences and partial sequence of mitochondrial cytochrome c oxidase subunit I (COI) gene were also analyzed. A total of 115 clones for rpS7 and 122 clones for ITS1 were obtained from 37 specimens. The nucleotide sequence length is 741 to 743 bp for rpS7 and 334 to 348 bp for ITS1. Intra- and inter-specimen variation in rpS7 results from nucleotide substitution, while such variation in ITS1 is mainly due to different numbers of short base repeats. The content of G + C is lower in rpS7 (43.5%) than in ITS1 (68.2%). Our results indicate that the proportion of the sequence variable sites is higher in rpS7 (61) than in ITS1 (23); the informative parsimony of rpS7 is evidently higher than that of ITS1 (26 vs. 2); the overall ratio between transitions and transversions in ITS1 is slightly lower than in rpS7, but remarkably lower than in COI. These results suggest that rpS7 is more suitable than ITS1 as a marker for genetic divergence of this group. Furthermore, gene flow is observed between the different geographic populations of C. nasus from the phylogeny of this species based on rpS7, showing that rpS7 has more evolutionary characteristics for understanding the processes of genomic evolution at the intraspecific level. [ABSTRACT FROM AUTHOR]

In this study, twelve polymorphic microsatellite markers were developed for Coilia ectenes (synonym C. nasus). In a sample of 30 C. ectenes individuals in a Wuhan population from Yangtze River, a total of 78 alleles were detected, and the number of alleles per locus ranged from 3 to 12. The observed and expected heterozygosities ranged from 0.100 to 1.000 and from 0.098 to 0.899, respectively. Six loci significantly deviated from the Hardy-Weinberg equilibrium after Bonferroni correction ( P < 0.004), and no significant linkage disequilibrium between pairs of loci was found. The applicability of these markers in a closely related species, C. mystus, was evaluated by cross-species amplification. These microsatellite markers will be useful in studies on population genetics, conservation genetics, and fishery management and in the construction of genetic linkage maps of C. ectenes and C. mystus. [ABSTRACT FROM AUTHOR]