Analysis of the genetic structure of the introduced clearhead icefish (Protosalanx chinensis) populations in northern China.

When species are introduced to a new environment, they can quickly adapt to the environment and may differ from the indigenous species. The indigenous population of Protosalanx chinensis has a high level of genetic diversity, but it is unclear on the genetic diversity of the introduced populations in northeast China, which supports the major production of P. chinensis in the world. A total of 556 individuals of P. chinensis were collected during 2016-2021, from Lianhuan Lake (LHL), Xingkai Lake (XK), and Shuifeng Reservoir (SF), and one population was collected from the indigenous Taihu Lake (TH). Overall, 36 haplotypes were detected, and the genetic differences in P. chinensis populations within and between river basins were investigated. The nucleotide diversity (π) of the populations ranged from 0.0005 to 0.0032, and the haplotype diversity (Hd) ranged from 0.455 to 0.890, with the highest genetic diversity in the TH population, followed by the SF population, and lower genetic diversity in the XK and LHL populations. The analysis of the genetic differentiation index (Fst) and the genetic distance between populations showed that there was significant genetic differentiation between the TH population and the other populations. More sampling points have been set up in LHL for further analysis; the Dalong Lake (DL) and the Xiaolong Lake (XL) populations were far from the other populations within the LHL population. In this study, we didn't find a correlation between population size, stability, and genetic diversity, and the ecological measures of management should be decisive to the population dynamics. These results provide a basis for the rational utilization and effective management of P. chinensis.

Age, growth, reproduction and mortality of Xenocypris argentea (Günther,1868) in the lower reaches of the Tangwang River, China.

To investigate various population biological parameters of Xenocypris argentea in the lower reaches of the Tangwang River (China), a comprehensive study was conducted for the first time. A total of 1,003 samples were collected from April to November 2022. The collected samples revealed that female X. argentea had total lengths ranging from 12.4 cm to 25.7 cm (weighing 15.86 g to 159.55 g), and male X. argentea had total lengths ranging from 10.8 cm to 23.9 cm (weighing 9.27 g to 121.06 g). The age of the samples was determined using otolith analysis, indicating that the ages ranged from 1 to 5 years old in both females and males. The length-weight relationships were further analyzed, uncovering the allometric growth index (b) was 3.1296 for females, indicating a positive allometric growth pattern. Differently, males exhibited a b value of 3.0274, suggesting an isometric growth pattern. Furthermore, the von Bertalanffy growth formula provided insights into the growth characteristics of X. argentea, revealing an asymptotic total length (L∞) of 36.096 cm and a growth coefficient (K) of 0.121. The analysis of the gonadal somatic index (GSI) and ovarian development period indicated that the spawning period occurred from April to July, with peak spawning in June. The study also explored fecundity-related traits, finding that individual absolute fecundity (FA) ranged from 11,364 eggs to 56,377 eggs, while eviscerated body weight relative fecundity (FW) ranged from 209 eggs/g to 823 eggs/g. The exploitation rate (E) for X. argentea was calculated as 0.574, suggesting that the population of X. argentea has been overexploited. By revealing previously unknown data on the key life history traits of X. argentea, this study has provided valuable insights that are crucial for the development of conservation strategies and policies.

[Resource differences in the populations of Protosalanx chinensis between Dalong Lake and Amuta Lake in Daqing, Northeast China]. / 大庆市大龙湖与阿木塔湖大银鱼种群资源差异.

The population structure of Protosalanx chinensis is affected by a variety of factors, including water environment, intraspecific differentiation, interspecific competition and commercial fishing. To investigate the growth performance and the current status of resource utilization of P. chinensis in two important fish farming grounds (Dalong Lake and Amuta Lake) in Daqing, Northeast China, we collected 1513 P. chinensis samples from April to December 2018 for measurement and recording the basic biological characteristics. We estimated the parameters including population growth, mortality and exploitation using Von Bertalanffy growth formula, Beverton-Holt model, Pauly's empirical formula and length-based Bayesian biomass estimation method. The results showed that the asymptotic body lengths of Dalong Lake (n=660) and Amuta Lake (n=853) populations were 183.75 and 169.10 mm, respectively. The growth performance indices were both 4.85, and the body mass growth equations were Wt=29.29×(1-e-2.1(t+0.07))3.2977 and Wt=28.72×(1-e-2.5(t+0.07))3.4168, respectively. The ages at inflection were 0.49 a and 0.43 a, and the condition factors were 5.30×10-4±1.38×10-4 and 4.00×10-4±1.61×10-4. The exploitation rates were 0.60 and 0.61, and the relative catch per unit of supplementation were 0.069 and 0.075, respectively. The current differences in population resources between Dalong Lake and Amuta Lake in Daqing were mainly manifested in the parameters related to growth characteristics. The main reason for such differences was changes in the survival conditions of P. chinensis populations after the period of dietary transition induced by the density differences.

Biochemical indices, gene expression, and SNPs associated with salinity adaptation in juvenile chum salmon (Oncorhynchus keta) as determined by comparative transcriptome analysis.

Chum salmon (Oncorhynchus keta) migrate from freshwater to saltwater, and incur developmental, physiological and molecular adaptations as the salinity changes. The molecular regulation for salinity adaptation in chum salmon is currently not well defined. In this study, 1-g salmon were cultured under 0 (control group, D0), 8‰ (D8), 16‰ (D16), and 24‰ (D24) salinity conditions for 42 days. Na+/K+-ATPase and Ca2+/Mg2+-ATPase activities in the gill first increased and then decreased in response to higher salinity environments where D8 exhibited the highest Na+/K+ATPase and Ca2+/Mg2+-ATPase activity and D24 exhibited the lowest. Alkaline phosphatase (AKP) activity was elevated in all salinity treatment groups relative to controls, while no significant difference in acid phosphatase (ACP) activity was observed across treatment groups. De novo transcriptome sequencing in the D0 and D24 groups using RNA-Seq analysis identified 187,836 unigenes, of which 2,143 were differentially expressed in response to environmental salinity (71 up-regulated and 2,072 down-regulated). A total of 56,020 putative single nucleotide polymorphisms (SNPs) were also identified. The growth, development, osmoregulation and maturation factors of N-methyl-D-aspartate receptors (nmdas) expressed in memory formation, as well as insulin-like growth factor 1 (igf-1) and igf-binding proteins (igfbps) were further investigated using targeted qRT-PCR. The lowest expression of all these genes occurred in the low salinity environments (D8 or D16), while their highest expression occurred in the high salinity environments (D24). These results provide preliminary insight into salinity adaptation in chum salmon and a foundation for the development of marker-assisted breeding for this species.

Estimation of Coregonus ussuriensis age, growth, and maturation in China's Amur River.

This study examined the age, growth, and maturation of 1,064 Coregonus ussuriensis individuals that were collected monthly from the middle section of the Amur River, China between 2016 and 2018. The fork length (FL) ranged from 14.9 to 49.1 cm for males and 21.5 to 58.8 cm for females, and the body weight (BW) ranged from 72.6 to 1,348.7 g for males and 107.9 to 2,854.9 g for females. The relationship of BW and FL was expressed as: BW♂ = 0.0324 × FL2.708; BW♀ = 0.014 × FL2.963. The sample ages ranged from 2 to 8 years for males and 2 to 9 years for females. We used the von Bertalanffy function based on otolith reading and observed FL data to simulate Coregonus ussuriensis growth, which has been suggested to be similar to that of other Salmonidae fishes. No significant difference in growth was determined between males and females. The monthly gonad somatic index (GSI) value ranged from 0.16% to 1.69% for males and from 0.73% to 16.15% for females, with a peak in November. Additionally, the reproductive staging suggested that the Coregonus ussuriensis spawning season was mainly in November and December. The size at maturity (FL50%) for males and females was 34.9 cm and 37.9 cm respectively, and the corresponding age (T50%) was 4.5 and 5.1, respectively. This study provides basic information for understanding the biological characteristics of Coregonus ussuriensis and should aid in the assessment and management of fishery resources.