The genus Silurus, an important group of catfish, exhibits heterogeneous distribution in Eurasian freshwater systems. This group includes economically important and endangered species, thereby attracting considerable scientific interest. Despite this interest, the lack of a comprehensive phylogenetic framework impedes our understanding of the mechanisms underlying the extensive diversity found within this genus. Herein, we analyzed 89 newly sequenced and 20 previously published mitochondrial genomes (mitogenomes) from 13 morphological species to reconstruct the phylogenetic relationships, biogeographic history, and species diversity of Silurus. Our phylogenetic reconstructions identified eight clades, supported by both maximum-likelihood and Bayesian inference. Sequence-based species delimitation analyses yielded multiple molecular operational taxonomic units (MOTUs) in several taxa, including the Silurus asotus complex (four MOTUs) and Silurus microdorsalis (two MOTUs), suggesting that species diversity is underestimated in the genus. A reconstructed time-calibrated tree of Silurus species provided an age estimate of the most recent common ancestor of approximately 37.61 million years ago (Ma), with divergences among clades within the genus occurring between 11.56 Ma and 29.44 Ma, and divergences among MOTUs within species occurring between 3.71 Ma and 11.56 Ma. Biogeographic reconstructions suggested that the ancestral area for the genus likely encompassed China and the Korean Peninsula, with multiple inferred dispersal events to Europe and Central and Western Asia between 21.78 Ma and 26.67 Ma and to Japan between 2.51 Ma and 18.42 Ma. Key factors such as the Eocene-Oligocene extinction event, onset and intensification of the monsoon system, and glacial cycles associated with sea-level fluctuations have likely played significant roles in shaping the evolutionary history of the genus Silurus.

The sterlet (Acipenser ruthenus) is one of the 27 sturgeon species and is well-known for its wide distribution and small body size in comparison to other sturgeons. For assessing the population genetics and parentage identification of sterlet, ten microsatellites developed for Chinese sturgeon and cross-amplified in sterlet were tested by 40 individuals of sterlet. The ten microsatellites were developed using transcriptome sequencing of Chinese sturgeon. The expected heterozygosity (HE), observed heterozygosity (HO), Shannon-Weiner diversity indices (H') and polymorphic information content (PIC) of the 10 microsatellites ranged from 0.466 to 0.751, from 0.438 to 0.938, from 0.66 to 1.51 and from 0.368 to 0.716, respectively. Combined exclusion probability based on the genotype of pair parent known (CE-PP), one parent known (CE-2P), and no parent known (CE-1P) of the 10 microsatellites were 99.99%, 99.96%, and 99.49%, respectively. These result showed that the 10 microsatellites should be helpful for assessing the population genetics and parentage identification of sterlet.

Length-to-weight and length-to-length relations were estimated for 15 freshwater fishes belonging to the order Cypriniformes from Yuxi power station to Kaitan reservoir dam trunk stream of the Oujiang River, Zhejiang Province, China. The following species were studied: Distoechodon tumirostris Peters, 1881, Xenocypris davidi Bleeker, 1871, Plagiognathops microlepis (Bleeker, 1871), Hemibarbus labeo (Pallas, 1776), Hemibarbus maculatus Bleeker, 1871, Chanodichthys erythropterus (Basilewsky, 1855), Culter alburnus Basilewsky, 1855, Chanodichthys dabryi (Bleeker, 1871), Opsariichthys bidens Günther, 1873, Zacco platypus (Temminck et Schlegel, 1846), Sinibrama macrops (Günther, 1868), Hemiculter leucisculus (Basilewsky, 1855), Pseudohemiculter hainanensis (Boulenger, 1900), Rhodeus sinensis Günther, 1868, and Squalidus argentatus (Sauvage et Dabry de Thiersant, 1874). The determination coefficients r2 of LWRs were all over 0.96, and the 15 values of parameter b were consistent with the predicted range of 2.5–3.5. The total length-to-standard length relations were also calculated with r2 ≥ 0.97. Our study provides new information on LWR for 1 species and LLRs for 8 species, as well as new maximum total length recorded for 4 species (i.e., Distoechodon tumirostris, Opsariichthys bidens, Pseudohemiculter hainanensis, and Rhodeus sinensis) in FishBase. This study is expected to provide a useful baseline for further studies of population parameters to improve management decisions on the Oujiang River.

The present study estimates length-weight relationships (LWRs) of fish species from the mainstream of the Yellow River, which is the largest sediment-laden river in the world. A total of 1168 specimens belonging to 4 families and 18 species were analysed. The following fish species were covered: Leuciscus chuanchicus (Kessler, 1876); Ctenopharyngodon idella (Valenciennes, 1844); Squaliobarbus curriculus (Richardson, 1846); Parabramis pekinensis (Basilewsky, 1855); Hemiculter leucisculus (Basilewsky, 1855); Culter alburnus (Basilewsky, 1855); Rhinogobio nasutus (Kessler, 1876); Hemibarbus maculatus (Bleeker, 1871); Cyprinus carpio (Linnaeus, 1758); Carassius auratus (Linnaeus, 1758); Hypophthalmichthys molitrix (Valenciennes, 1844); Hypophthalmichthys nobil (Richardson, 1845); Gymnocypris eckloni (Herzenstein, 1891); Schizopygopsis pylzovi (Kessler, 1876); Triplophysa siluroides (Herzenstein, 1888); Silurus lanzhouensis (Chen, 1977); Silurus asotus (Linnaeus, 1758); Channa argus (Cantor, 1842). The b values of the LWRs ranged from 2.598 for Ctenopharyngodon idella to 3.271 for Parabramis pekinensis. This study represents the first report on LRWs of commercial fish species in the whole mainstream of the Yellow River.The LRWs of five species have not been previously record. These data can serve as important baseline for conservation and management in the Yellow River fishery resources, which is very useful for evaluation of the status of the river ecological health.

Background Chinese soft-shell turtle ( Pelodiscus sinensis ) is an important commercial species for their high nutritional value and unique taste, but it has been a vulnerable species due to habitat loss. In this study, homologous juvenile turtles were allocated to lake, pond and paddy field to investigate the habitat effects on turtles. Results The growth, morphology and gut microbial communities were monitored during the 4 months cultural period. It showed higher growth rate of turtles in paddy field and pond. The appearance, visceral coefficients, gut morphology and microbial communities in turtles were distinct among different habitats. The microbial community richness on Chao1 was obviously lower in initial turtle guts from greenhouses, whereas it was relative higher in turtle guts sampled from paddy fields than ponds and lake. Significant differences on dominant microbes were found among initial and subsequent samples from different habitats. Firmicutes was the most abundant phylum in the guts of turtles sampled from the greenhouse initially, while Proteobacteria was the most abundant phylum after cultivation in different habitats, followed by Bacteroidetes. The microbial composition were distinct in different habitats at 60d, and the appearance of dominant phyla and genera was more driven by sampling time than habitats at 120d. Both the sampling time and habitats affected the appearance of dominant phyla and genera during the cultivation. The functional predictions indicated that both habitat type and sampling time had significant effects on metabolic pathways, especially amino acid and carbohydrate metabolism. Conclusions The turtles could adapt to natural lakes, artificial ponds and paddy fields. The gut microbial abundance was different among the habitats and sampling time. The species of microbes were significantly more diverse in paddy field specimens than in those from ponds and lakes. Rice-turtle coculture is a potential ecological and economic farming mode that plays important roles in wild turtle protection and food security.

Invasions of non-native fishes are recognized as a serious threat to freshwater biodiversity across the globe. Being the China's second-largest river, the Yellow River has experienced severe invasion pressure of non-native fishes during recent decades. However, much less is known about species composition and distribution of non-native fishes in this river basin. Here, we investigated and summarized the literatures about non-native freshwater fish in the Yellow River Basin (YRB), to examine their taxonomic diversity, geographical origin, longitudinal distribution and potential risk. We found that 40 non-native fish species, belonging to 9 orders, 18 families and 35 genera, have invaded the YRB. Of which 19 exotic species came from other regions, while 21 translocated species were introduced into the upstream from midstream and downstream of the YRB. The aquaculture was the main vectors responsible for non-native fish introductions. An average of 8.24 non-native fish species was introduced and established per sub-region, accounting for 25.5 % of total fish species. The percentage of non-native species showed a significant unimodal model against average elevation, with the highest values (ca. 70 %) in upstream mainstream reaches and tributaries. Non-native species from historically absent or species-poor orders (Salmoniformes, Osmeriformes and Perciformes) were the most successful invaders. Furthermore, the species composition of non-native fishes changed markedly along the longitudinal gradient (i.e., from source region to downstream). The negative impacts of non-native fish introductions to native fish species, e.g., competition for resource, predation and hybridization were emerged in many introduce regions and could get worse in the future due to global warming and human activities. This study can help improve the management of non-native fish introductions and biodiversity conservation of native and endemic fish species in the YRB.

The length-weight relationships (LWRs) were determined for two native cyprinid fishes: Poropuntius opisthopterus (Wu, 1977) and Raiamas christyi (Boulenger, 1920) collected from the upper reaches of Nujiang River (31 degrees 33'29"N; 92 degrees 55'58"E), Southwest of China. A total of 162 specimens were collected quarterly between March 2015 and November 2016. Fish were sampled by electrofishing in 12 wadable sites with maximum water depth 60-70 cm. The b values parameter in the length-weight relationship equations were calculated as 2.90 for P.opisthopterus and 3.45 for R.christyi. This study represents a new maximum standard length record for P.opisthopterus.

This paper describes an experimental study on the seismic performance of steel reinforced concrete (SRC) T-shaped columns. The lateral loads were applied along the web of the column with different loading histories, such as monotonic loading, mixed loading of variable amplitude cyclic loading and monotonic loading, constant amplitude cyclic loading and variable amplitude cyclic loading. The failure modes, load-displacement curves, characteristic loads and displacements, ductility, strength and stiffness degradations and energy dissipation capacity of the column were analyzed. The effects of loading history on the seismic performance were focused on. The test results show that the specimens behaved differently in the aspects of the failure mode subject to different loading history, although all the failure modes can be summarized as flexural failure. The hysteretic loops of specimens are plump, and minimum values of the failure drift angles and ductility coefficients are 1/24 and 4.64, respectively, which reflect good seismic performance of SRC T-shaped column. With the increasing numbers of loading cycles, the column reveals lower bearing capacity and ductility. The strength and stiffness of the column with variable amplitude cyclic loading degrades more rapidly than that with constant amplitude cyclic loading, and the total cumulative dissipated energy of the former is less.

SummaryA simple analytical solution of a one‐dimensional transient and nonlinear Richards equation is of great importance for estimating the hydraulic properties of soil and for precision irrigation. We developed simple approximate solutions in explicit and implicit forms for equations describing one‐dimensional, constant‐water‐head horizontal absorption and vertical infiltration for a special case of an exponential water‐retention curve and power‐law hydraulic conductivity, respectively, based on least‐action and variational principles. The profile of the soil water content (SWC) depended on the soil hydraulic parameter n associated with the pore‐size distribution, and the new solutions could be applied to most soils for 3.5 ≤ n ≤ 24.5. A comparison with numerical solutions calculated by an implicit‐difference scheme indicated that the approximate solution in explicit form accurately estimated the special hydraulic‐function parameters for calculating the SWC profile, cumulative infiltration, infiltration rate and wetting‐front distance in horizontal‐absorption experiments. An approximate solution in implicit form was also obtained with Nth order Taylor‐series expansions for an equation describing one‐dimensional, constant‐water‐head vertical infiltration. A large N was used to simulate SWC for soils with a large n, but this did not influence estimates of cumulative infiltration. The relation between infiltration rate and the inverse wetting‐front depth was not strictly linear for vertical infiltration, and the implicit method could be used to describe this nonlinear relation.Highlights A simple solution of the Richards equation is important to research soil water infiltration. Least‐action and variational principles were used to analyse soil water content distribution. Analytical solutions of a nonlinear Richards equation by special hydraulic functions were proposed. A method was proposed to predict the infiltration and estimate soil hydraulic parameters.

In the middle of the South-North Water Diversion Project lies the Yellow River Crossing Tunnel Project, which is a long-distance, deep-buried, pressured water-conveyance tunnel that crosses the river bed of the Yellow River. This project is the key controlling project of the middle route scheme. The project contains a bilayer composite lining structure: the external lining is reinforced concrete, and the internal lining is a 45 cm-thick anchor ring prestressed concrete. This structure has thin concrete lining thickness, high ring anchor curvature, and high tensile stress. In this study, the composite lining structure of the Yellow River crossing tunnel was evaluated using the 3D finite element method to examine the mechanical characteristics of this new structure type. The analysis examines the construction period, the water-filling operation period, and the complete water head operation period to evaluate the deformation and force transfer mechanism of the external lining segment and the prestressed internal lining ring anchor. The results showed that the bilayer composite lining possessed individual load-carrying characteristics. The tunnel exhibited excellent deformation under internal and external water pressure. The study also found that this approach satisfied safety standards.

Water pressure test can evaluate the permeability of material. But because of the tunnel in Yellow River crossing project of the mid-route of South-to-north water transfer project with large, pressure pipeline and deep-depth tunnel, and also inner and outer lining of the tunnel must be under high pressure, so it makes the water pressure test is complicated and difficult to operate. Test in stages, selection of test site, selection of test materials and test equipment, also the inspection of water tightness, have become the main content of this experimental study. In chronological order, the content of this test is: first, inside the tunnel the bolt pressure rubber strip method is used for pressure water test, the results show that the bolt rubber strip cannot prevent seepage of water. Then, on the outside of the tunnel, different seepage control material and process is used for pressure water test outside the holes on the ground, polyurea material is preliminary selected as seepage control material. Again, polyurea material is used as seepage control material for pressure water test inside the tunnel, impervious materials and process is selected; Finally, inside the tunnel, 10% of the total number of joint seam is selected for productive water pressure test, the final test results show that, the seepage control measures of spraying polyurea is reliable, and comply with the design requirements.

Rock carp is an endemic fish in the upper Yangtze River basin. Its populations have dramatically declined in the recent years due to human activities, such as overfishing and damming. In the present study, with the aim to give suggestions for better conservation, we investigated age, growth, and reproductive biology of the rock carp using samples collected between 2007 and 2013 from the Chishui River. The results indicate that there are no significant differences between the length–weight relationships of females and males (W = 0.015SL3.155). The von Bertalanffy growth curves computed by the observed length-at-age data could be expressed as L t  = 64.9(1 − e−0.101(t+0.217)). The estimated length at 50 % sexual maturity for males is 24.2 cm (approximately aged 4) and 37.0 cm for females. Female gonad analysis suggests that rock carp is a batch spawner, which can spawn at least twice during the reproductive season, from April to August. Standard length and age of 86.5 % individuals were below 25 cm and 4 years, respectively, indicating that the exploitation is too intensive and that populations are undergoing miniaturization. These data corroborate that a combination of natural and anthropogenic factors has caused a sharp decline in wild populations during recent years, calling for immediate design and implementation of conservation measures for this species.