Molecular phylogenetic analysis of the East Asian hemicultrine fishes (Teleostei: Cyprinidae: Xenocypridinae), with suggestions to their generic classification and redescription of the recently described species Hemiculter yungaoi Vasil'eva et al. 2022.

The hemicultrine fishes are a group of small-sized cyprinids, widely distributed but endemic to East Asian rivers and lakes. Till now, the taxonomic boundaries and relationships within this group remain poorly explored. In the present study, we study the phylogeny of this group, providing suggestions for classification of the hemicultrine group. Using two mitochondrial and three nuclear genes, and samples representing all genera, our results showed that the group consists of seven major lineages, of which four (Hemiculterella, Hainania, Pseudolaubuca, and Anabarilius) were monophyletic and three (Hemiculter, Toxabramis, and Pseudohemiculter) were not. Based on the phylogenetic tree, we redefined the genera. We revive the genus Siniichthys, which has three species, Siniichthys bleekeri, Siniichthys lucidus, and S. varpachovskii, that were previously treated as members of the genus Hemiculter but showed distant relationships to the genus Hemiculter in our phylogenetic tree. With the new results, a diagnostic key for clades of the hemicultrine group is provided. Furthermore, we provide more detailed information on diagnostic features of the recently described species Hemiculter yungaoi (Vasil'eva et al., 2022). This work will facilitate future systematic studies, pave the way for evolutionary studies, and provide valuable information for the urgent conservation of hemicultrine fishes.

Deterministic Generation of Orbital-Angular-Momentum Multiplexed Tripartite Entanglement.

We demonstrate the experimental generation of orbital angular momentum (OAM) multiplexed multipartite entanglement with cascaded four-wave mixing processes in a continuous variable (CV) system. In particular, we implement the simultaneous generation of 9 sets of OAM multiplexed tripartite entanglement over 27 Laguerre-Gauss (LG) modes, as well as 20 sets of OAM multiplexed bipartite entanglement over 40 LG modes, which show the rich entanglement structure of the system. In addition, we also generate tripartite entanglement of three types of coherent OAM superposition modes. Such OAM multiplexed multipartite entanglement opens the avenue to construct CV parallel quantum network for realizing parallel quantum information protocols.

Gene Flow and Individual Relatedness Suggest Population Spatial Connectivity of Sinogastromyzon sichangensis (Cypriniformes: Balitoridae) in the Chishui River, China.

Sinogastromyzon sichangensis is a hillstream loach endemic to the upper Yangtze River, China. It is unclear whether this fish lives in a very restricted area or may be dispersed over a long distance. In the present study spatial connectivity of populations of S. sichangensis was investigated based on 343 individuals collected from 12 sites of Chishui River and employing 22 microsatellite loci. The results of genetic diversity analysis showed that observed heterozygosity (HO) and polymorphism information content (PIC) ranged from 0.5653 to 0.6999 and 0.8513 to 0.8819, respectively. Population structure analysis suggested that S. sichangensis had an unclear genetic structure. AMOVA showed that 69.36% of genetic variation was attributed to differentiation within individuals and all the pairwise genetic differentiation indices (FST) were low (mean FST = 0.0344), indicating weak differentiation among these populations. Estimation of gene flow showed frequent flow among populations, and contemporary levels (mean contemporary migration rate, mc = 0.0131) were approximately equal to historical levels (mean historical migration rate, mh = 0.0147). Individual relatedness analysis revealed a high level of sibship within and among different populations. The frequent gene flow and widespread sibship were due to S. sichangensis laying drifting eggs which travel for a long distance until hatching, after which the juveniles or adults migrate upstream. The results of unclear geographic structure and frequent exchange also indicate that it is necessary to decrease the negative impacts of anthropogenic activities on the connectivity of rivers to protect the migration routes of S. sichangensis.

Geological events and Pliocene climate fluctuations explain the phylogeographical pattern of the cold water fish Rhynchocypris oxycephalus (Cypriniformes: Cyprinidae) in China.

BACKGROUND: Rhynchocypris oxycephalus is a cold water fish with a wide geographic distribution including the relatively warm temperate regions of southern China. It also occurs in second- and third-step geomorphic areas in China. Previous studies have postulated that high-altitude populations of R. oxycephalus in southern China are Quaternary glacial relics. In this study, we used the mitochondrial gene Cytb and the nuclear gene RAG2 to investigate the species phylogeographical patterns and to test two biogeographic hypotheses: (1) that divergence between lineages supports the three-step model and (2) climatic fluctuations during the Quaternary resulted in the present distribution in southern China. RESULTS: Phylogenetic analysis detected three major matrilines (A, B, and C); with matrilines B and C being further subdivided into two submatrilines. Based on genetic distances and morphological differences, matriline A potentially represents a cryptic subspecies. The geographic division between matrilines B and C coincided with the division of the second and third geomorphic steps in China, suggesting a historical vicariance event. Pliocene climatic fluctuations might have facilitated the southwards dispersal of R. oxycephalus in matriline C, with the subsequent warming resulting in its split into submatrilines C1 and C2, leaving submatriline C2 as a relic in southern China. CONCLUSIONS: Our study demonstrates that geological events (three steps orogenesis) and climate fluctuations during the Pliocene were important factors in shaping phylogeographical patterns in R. oxycephalus. Notably, no genetic diversity was detected in several populations, all of which possessed unique genotypes. This indicates the uniqueness of local populations and calls for a special conservation plan for the whole species at the population level.

Effects of water temperature and discharge on natural reproduction time of the Chinese sturgeon, Acipenser sinensis, in the Yangtze River, China and impacts of the impoundment of the Three Gorges Reservoir.

Chinese sturgeon, Acipenser sinensis, is a critically endangered anadromous fish species spawning in the Yangtze River of China during October and November. In this study, we analyzed the effects of hydrological factors, such as water temperature and discharge, on the natural reproduction time of the Chinese sturgeon and evaluated the impact of the impoundment of the Three Gorges Reservoir (TGR) based on our survey data from 1998 to 2011. The results showed that the first spawning dates were significantly (P < 0.05) correlated with the date of water temperature reaching 20°C (20°C WT dates), October mean discharge (Oct. discharge), and the discharge change from October to November (Oct-Nov Δdischarge). Regression analysis suggested that one day delay of 20°C WT dates could postpone the first spawning date by 0.673 days. A discharge increase of 1000 m(3)s(-1) in October could bring forward the first spawning date by two days. Our results also indicated that the impoundment of the TGR had delayed the first spawning time due to water temperature lag and flow regulation. We suggest the following ecological regulations in order to facilitate conservation of the Chinese sturgeon: to eliminate water temperature lag by regulating water temperature downstream of the Three Gorges Dam (TGD), to enhance water discharge downstream in October, and to complete impoundment before October.

Molecular phylogeny and conservation priorities of the subfamily Acheilognathinae (Teleostei: Cyprinidae).

It is increasingly accepted that conservation work should consider the evolutionary history of target species. Fishes in the subfamily Acheilognathinae, family Cyprinidae, are, with the exception of three species exclusively distributed in Europe, restricted to Asia and show a distinct spawning behavior in laying their eggs in gill chambers of freshwater mussels. At present, many of the 70 species recognized in this group are facing with serious population decline in China and Japan, and their phylogenetic relationships are not well resolved. In the present study, based on mtDNA cyt b and 12S rRNA gene sequences, we reconstructed a more detailed species-level phylogenetic tree of this group, and assessed species conservation priorities based on their evolutionary distinctiveness. Molecular phylogenetic analyses showed that the Acheilognathinae contains two major clades: Acheilognathus clade and Tanakia-Rhodeus clade. Based on this phylogenetic result, conservation priority analyses were conducted using ED (evolutionary distinctiveness)/HED (heightened evolutionary distinctiveness), and EDGE (evolutionary distinctiveness and global endangeredness)/HEDGE (heightened evolutionary distinctiveness and global endangeredness) methods. The results suggested that T. himantegus, T. lanceolata, A. gracilis, A. imberbis, T. tanago, and A. longipinnis should be ranked as the top-priority species for conservation. According to our results, we also discussed the current conservation efforts of the bitterling fishes and gave suggestions for future work.

Screening and combination selection of multifunctional actinomycetes for aerobic composting.

IMPORTANCE: With the development of animal husbandry in China, the production of a large amount of livestock and poultry manure has become one of the main agricultural pollution sources. High-temperature aerobic composting stands out as one of the most crucial methods for the safe and resourceful utilization of livestock and poultry manure, serving as an essential link between crop cultivation, animal breeding, and sustainable agricultural development. Numerous studies have demonstrated that the addition of exogenous multifunctional bacterial agents to compost reduces not only harmful emissions but also sequesters or increases essential nutrients. However, these efficacies depend on the specific functions of the bacteriophage itself, the harmonization and complementarity within the colony, and its ability to adapt to the environment. In recent years, relatively few studies have been conducted on actinomycetes. This experiment provides excellent actinomycete resources for the production of high-efficiency and high-quality compost compound microbial agents of manure and straw.

The parasites of a successful invader: monogeneans of the Asian topmouth gudgeon Pseudorasbora parva, with description of a new species of Gyrodactylus.

Monogenean parasites are often co-introduced with their fish hosts into novel areas. This study confirmed co-introduction of two dactylogyrids, Dactylogyrus squameus Gusev, 1955 and Bivaginogyrus obscurus (Gusev, 1955), and a newly described gyrodactylid species, Gyrodactylus pseudorasborae n. sp. into Europe along with their fish host, the invasive topmouth gudgeon Pseudorasbora parva (Temminck & Schlegel) from East Asia. All three species were observed in the lower Dnieper and middle Danube basin regions and had slightly larger haptoral hard parts than the same parasites in their native range. While dactylogyrids occurred sporadically, we recorded regular infection by G. pseudorasborae n. sp. at relatively high prevalence and abundance. This latter species was observed in both the native and non-native range of topmouth gudgeon, and resembles Gyrodactylus parvae You et al., 2008 recently described from P. parva in China. Both species were distinguished based on genetic analysis of their ITS rDNA sequence (6.6% difference), and morphometric differences in the marginal hooks and male copulatory organ. Phylogenetic analysis of dactylogyrid monogeneans showed that B. obscurus clustered with Dactylogyrus species parasitising Gobionidae and Xenocyprididae, including D. squameus, supporting recent suggestions of a paraphyletic origin of the Dactylogyrus genus. In addition to co-introduced parasites, topmouth gudgeon was infected with a local generalist, G. prostae Ergens, 1964, increasing the number of monogeneans acquired in Europe to three species. Nevertheless, monogenean infections were generally lower in non-native host populations, potentially giving an advantage to invading topmouth gudgeon.

Title: Les parasites d'un envahisseur à succès : les monogènes du goujon asiatique Pseudorasbora parva, avec description d'une nouvelle espèce de Gyrodactylus. Abstract: Les parasites monogènes sont souvent co-introduits avec leurs hôtes poissons dans de nouvelles zones. Cette étude a confirmé la co-introduction de deux Dactylogyridae, Dactylogyrus squameus Gusev, 1955 et Bivaginogyrus obscurus (Gusev, 1955), et d'une espèce de Gyrodactylidae nouvellement décrite, Gyrodactylus pseudorasborae n. sp. en Europe, en même temps que leur hôte poisson, le goujon envahissant Pseudorasbora parva (Temminck & Schlegel) qui vient d'Asie de l'Est. Les trois espèces ont été observées dans les régions du bas Dniepr et du bassin moyen du Danube et avaient des parties sclérifiées haptorales légèrement plus grandes que les mêmes parasites dans leur aire de répartition d'origine. Alors que les Dactylogyridae étaient rares, nous avons enregistré une infection régulière par G. pseudorasborae n. sp. à une prévalence et une abondance relativement élevées. Cette dernière espèce a été observée à la fois dans l'aire de répartition indigène et non indigène du goujon asiatique et ressemble à Gyrodactylus parvae You et al., 2008 récemment décrit chez P. parva en Chine. Les deux espèces ont été distinguées sur la base de l'analyse génétique de leur séquence ITS de l'ADNr (différence de 6,6 %) et des différences morphométriques dans les crochets marginaux et l'organe copulateur mâle. L'analyse phylogénétique des monogènes Dactylogyridae a montré que B. obscurus se regroupait avec des espèces de Dactylogyrus parasitant les Gobionidae et les Xenocyprididae, y compris D. squameus, soutenant les suggestions récentes d'une origine paraphylétique du genre Dactylogyrus. En plus des parasites co-introduits, le goujon asiatique était infecté par un généraliste local, G. prostae Ergens, 1964, portant le nombre de monogènes acquis en Europe à trois espèces. Néanmoins, les infections par les monogènes étaient généralement plus faibles dans les populations d'hôtes non indigènes, donnant potentiellement un avantage à l'invasion du goujon asiatique.

Discovery of a wild, genetically pure Chinese giant salamander creates new conservation opportunities.

Effective conservation of threatened biota relies on accurate assessments and scientific guidance. As an unfortunate example, Chinese giant salamanders ( Andrias, CGS) remain critically endangered in nature. Misguided conservation efforts, e.g., commercial propagation and releasing of millions of likely non-indigenous or interspecific hybrids, have further compromised conservation initiatives. Limited information on wild populations of CGS poses a significant conservation challenge. Following 18-month long field monitoring, we now report the discovery of a wild population of CGS in a closed nature reserve in Jiangxi Province, China. Genomic assessments reveal its genetic distinctiveness and do not detect genetic admixture with other species. Based on morphological and molecular evidences, we describe this CGS as a new species Andrias jiangxiensis sp. nov. This is the only known species of CGS today with a genetically pure, reproducing, in situ population. This discovery emphasizes the important role that closed nature reserves play in protecting species, and the necessity of integrating long-term field monitoring and genetic assessments. It sets a new pathway for discovering and conserving endangered species, especially for those biotas that are similarly being extirpated by anthropogenic translocations and overexploitation.

Phylogeny of the gudgeons (Teleostei: Cyprinidae: Gobioninae).

The members of the cyprinid subfamily Gobioninae, commonly called gudgeons, form one of the most well-established assemblages in the family Cyprinidae. The subfamily is a species-rich group of fishes, these fishes display diverse life histories, appearances, and behavior. The phylogenetic relationships of Gobioninae are examined using sequence data from four loci: cytochrome b, cytochrome c oxidase I, opsin, and recombination activating gene 1. This investigation produced a data matrix of 4114 bp for 162 taxa that was analyzed using parsimony, maximum likelihood, and Bayesian inference methods. The phylogenies our analyses recovered corroborate recent studies on the group. The subfamily Gobioninae is monophyletic and composed of three major lineages. We find evidence for a Hemibarbus-Squalidus group, and the tribes Gobionini and Sarcocheilichthyini, with the Hemibarbus-Squalidus group sister to a clade of Gobionini-Sarcocheilichthyini. The Hemibarbus-Squalidus group includes those two genera; the tribe Sarcocheilichthyini includes Coreius, Coreoleuciscus, Gnathopogon, Gobiocypris, Ladislavia, Paracanthobrama, Pseudorasbora, Pseudopungtungia, Pungtungia, Rhinogobio, and Sarcocheilichthys; the tribe Gobionini includes Abbottina, Biwia, Gobio, Gobiobotia, Huigobio, Microphysogobio, Platysmacheilus, Pseudogobio, Romanogobio, Saurogobio, and Xenophysogobio. The monotypic Acanthogobio is placed into the synonymy of Gobio. We tentatively assign Belligobio to the Hemibarbus-Squalidus group and Mesogobio to Gobionini; Paraleucogobio and Parasqualidus remain incertae sedis. Based on the topologies presented, the evolution of swim bladder specializations, a distinctive feature among cyprinids, has occurred more than once within the subfamily.

Acheilognathus changtingensis sp. nov., a new species of the cyprinid genus Acheilognathus (Teleostei: Cyprinidae) from Southeastern China based on morphological and molecular evidence.

A new species of the bitterling genus Acheilognathus, Acheilognathus changtingensis sp. nov., was recently discovered from Changting County in Hanjiang River, Fujian Province, Southeastern China. It can be diagnosed by the following combination of characters: dorsal fin with three simple and 15 (occasionally 14) branched fin rays, anal fin with three simple and 12 (occasionally 11) branched fin rays; dorsal fin pale and anal fin slightly pale; white spots on anal-fin rays forming a transverse band, and anal fin margined with white band in males. Its unique characters are the many dispersed black spots on the dorsal, anal, pelvic, caudal fins, and on the head. Using the mitochondrial cytochrome Jb gene as a molecular marker, we reconstructed phylogenetic trees of A. changtingensis sp. nov. and other species in Acheilognathus to confirm its taxonomic status and study its speciation. Analyses of both morphological and molecular data consistently indicated the taxonomic status of the present new species. The results also show that A. changtingensis sp. nov. and Acheilognathus macropterus are sister species that diverged about 14.50 MYA by geographical isolation.

Extraordinarily thick-boned fish linked to the aridification of the Qaidam Basin (northern Tibetan Plateau).

Scattered with numerous salt lakes and approximately 2,700-3,200 m above sea level, the giant Qaidam inland basin on the northern Tibetan Plateau has experienced continuing aridification since the beginning of the Late Cenozoic as a result of the India-Asia plate collision and associated uplift of the Tibetan Plateau. Previous evidence of aridification comes mainly from evaporite deposits and salinity-tolerant invertebrate fossils. Vertebrate fossils were rare until recent discoveries of abundant fish. Here, we report an unusual cyprinid fish, Hsianwenia wui, gen. et sp. nov., from Pliocene lake deposits of the Qaidam Basin, characterized by an extraordinarily thick skeleton that occupied almost the entire body. Such enormous skeletal thickening, apparently leaving little room for muscles, is unknown among extant fish. However, an almost identical condition occurs in the much smaller cyprinodontid Aphanius crassicaudus (Cyprinodonyiformes), collected from evaporites exposed along the northern margins of the Mediterranean Sea during the Messinian desiccation period. H. wui and A. crassicaudus both occur in similar deposits rich in carbonates (CaCO(3)) and sulfates (CaSO(4)), indicating that both were adapted to the extreme conditions resulting from the aridification in the two areas. The overall skeletal thickening was most likely formed through deposition of the oversaturated calcium and was apparently a normal feature of the biology and growth of these fish.

Spatial and seasonal patterns of fish assemblages in mountain streams of the Ren River, southwest China.

The spatial-temporal patterns of fish assemblages in lotic systems can provide useful information in developing effective conservation measures. This study aimed to explore the spatial and seasonal changes in fish assemblages and their association with environmental factors in mountain streams of the Ren River, southwest China. Field investigations were conducted at 18 sites during the rainy and dry seasons in 2017. A total of 1,330 individuals, belonging to three orders, eight families, 19 genera, and 21 species, were collected. Analysis of similarities (ANOSIM) showed that the structure of fish assemblages varied significantly at the spatial scale, but not at the seasonal scale. In low-order sites, fish assemblages were mainly dominated by cold-water and rheophilic species (e.g., Rhynchocypris oxycephalus, Scaphesthes macrolepis, Metahomaloptera omeiensis, and Gnathopogon herzensteini), while those in high-order sites were predominated by warm-water and eurytopic or stagnophilic species (e.g., Squalidus argentatus, Hemiculter leucisculus, and Zacco platypus). Canonical correspondence analysis (CCA) showed that the fish assemblages were structured by a combination of large-scale landscape factors (e.g., altitude and C-link) and small-scale habitat features (e.g., channel width, water temperature, and depth). Among these factors, landscape had the greatest influence on fish assemblages, while local habitat variables were less important or were only significant in certain seasons.

Using environmental DNA methods to improve detectability in an endangered sturgeon (Acipenser sinensis) monitoring program.

BACKGROUND: To determine the presence and abundance of an aquatic species in large waterbodies, especially when populations are at low densities, is highly challenging for conservation biologists. Environmental DNA (eDNA) has the potential to offer a noninvasive and cost-effective method to complement traditional population monitoring, however, eDNA has not been extensively applied to study large migratory species. Chinese sturgeon (Acipenser sinensis), is the largest anadromous migratory fish in the Yangtze River, China, and in recent years its population has dramatically declined and spawning has failed, bringing this species to the brink of extinction. In this study, we aim to test the detectability of eDNA methods to determine the presence and relative abundance of reproductive stock of the species and whether eDNA can be used as a tool to reflect behavioral patterns. Chinese sturgeon eDNA was collected from four sites along the spawning ground across an eight month period, to investigate the temporal and spatial distribution using droplet digital PCR (ddPCR). RESULTS: We designed a pair of specific primers for Chinese sturgeon and demonstrated the high sensitivity of ddPCR to detect and quantify the Chinese sturgeon eDNA concentration with the limit of detection 0.17 copies/µl, with Chinese sturgeon eDNA been intermittently detected at all sampling sites. There was a consistent temporal pattern among four of the sampling sites that could reflect the movement characteristics of the Chinese sturgeon in the spawning ground, but without a spatial pattern. The eDNA concentration declined by approximately 2-3 × between December 2018 and December 2019. CONCLUSIONS: The results prove the efficacy of eDNA for monitoring reproductive stock of the Chinese sturgeon and the e decreased eDNA concentration reflect that Chinese sturgeon may survive with an extremely small number of reproductive stock in the Yangtze River. Accordingly, we suggest future conservation measures should focus on both habitat restoration and matured fish restocking to ensure successful spawning. Overall, this study provides encouraging support for the application of eDNA methods to monitor endangered aquatic species.

Whole genome sequencing of silver carp (Hypophthalmichthys molitrix) and bighead carp (Hypophthalmichthys nobilis) provide novel insights into their evolution and speciation.

The edible silver carp (Hypophthalmichthys molitrix) and bighead carp (H. nobilis), which are two of the "Four Domesticated Fish" of China, are cultivated intensively worldwide. Here, we constructed 837- and 845-Mb draft genome assemblies for the silver carp and the bighead carp, respectively, including 24,571 and 24,229 annotated protein-coding genes. Genetic maps, anchoring 71.7% and 83.8% of all scaffolds, were obtained for the silver and bighead carp, respectively. Phylogenetic analysis showed that the bighead carp formed a clade with the silver carp, with an estimated divergence time of 3.6 million years ago; the time of divergence between the silver carp and zebrafish was 50.7 million years ago. An East Asian cyprinid genome-specific chromosome fusion took place ~9.2 million years after this clade diverged from the clade containing the common carp and Sinocyclocheilus. KEGG and GO analyses indicated that the expanded gene families in the silver and bighead carp were associated with diseases, the immune system and environmental adaptations. Genomic regions differentiating the silver and bighead carp populations were detected based on the whole-genome sequences of 42 individuals. Genes associated with the divergent regions were associated with reproductive system development and the development of primary female sexual characteristics. Thus, our results provided a novel systematic genomic analysis of the East Asian cyprinids, as well as the evolution and speciation of the silver carp and bighead carp.

Seasonal variation in drifting eggs and larvae in the upper Yangtze, China.

From 5 March to 25 July 2008, ichthyoplankton drifting into the Three Gorges Reservoir from the upper reaches of the Yangtze River were sampled daily to investigate the species composition, abundance, and seasonal variation in early-stage fishes in this area. Twenty-eight species belonging to five orders and 17 families or subfamilies were identified by analyzing fish eggs and larvae, and a total of 14.16 billion individuals were estimated drifting through the sampling section during the investigation. Among the ichthyoplankton sampled, species in Cultrinae, Cobitidae, Gobioninae and Gobiidae, along with the common carp (Cyprinus carpio Linnaeus), comprised 89.6% of the total amount. Six peaks of drift density were identified during the sampling period, and a significant correlation was found between drift density with water discharge. The dominant species were different in each drift peak, indicating different spawning times for the major species. The total amount of the four major Chinese carps that drifted through the sampling section was estimated as 0.88 billion, indicating an increase in the population sizes of these species in the upper reaches of the Yangtze River after construction of the Three Gorges Dam. Actually, these reaches have become the largest spawning area for the four major Chinese carps in the Yangtze River. The large total amount of eggs and larvae drifting through this section demonstrated that the upper reaches of the Yangtze River provided important spawning sites for many fish species, and that conservation of this area should be of great concern.

Genetic diversity and reproductive success of a wild population of Chinese sturgeon ( Acipenser sinensis) from the Yangtze River inferred from juveniles born in 2014.

The Chinese sturgeon ( Acipenser sinensis Gray, 1835) is a large anadromous fish species, which is under considerable threat due to dramatic declines in population numbers. In the current study, population genetic diversity and individual reproductive success were assessed using nuclear microsatellite markers (simple sequence repeat, SSR) and complete mitochondrial (mtDNA) genome analysis of juveniles born in 2014. Results showed the existence of size polymorphism in the mtDNA genome of Chinese sturgeon, which was caused by a repeat motif. Population genetic diversity was high based on both SSR ( Ho: 0.728±0.211; He: 0.779±0.122) and mtDNA genome analyses ( H: 0.876±0.0035; Pi: 0.0011±0.0010). A positive inbreeding coefficient ( FIS: 0.066±0.143) was also found, indicating the occurrence of inbreeding. Reconstruction of sibling groups identified 11 mothers and 11 fathers involved in reproduction of Chinese sturgeons in 2014. Variance in individual reproductive success was not significant, with reproductive success of parent fish instead shown to be relatively even ( P=0.997>0.05), thus suggesting the absence of sweepstakes reproductive success (SRS). These results indicate that, in regard to conservation, loss of genetic diversity due to the effects of SRS is not of particular concern. However, we must focus on having an adequate number of adults and suitable environmental conditions to ensure that fish can reproduce.

Changes in taxonomic and functional diversity of fish communities after catastrophic habitat alteration caused by construction of Three Gorges Dam.

Habitat alterations that result from anthropogenic disturbance impact both the abiotic and biotic conditions of ecosystems, causing changes in biodiversity in many parts of the world. Recently, the use of functional diversity has been suggested as an approach to better evaluate the effects of such disturbance on particular communities. Here, we investigated the temporal changes in species and functional diversities of fish communities in the downstream area of the Three Gorges Dam (TGD) before, during, and after impoundment. We found two regime shifts in the fish community in 2004 and 2013 following impoundment. Although taxonomic diversity declined sharply at the first regime shift, it increased at the second shift. On the other hand, functional diversity declined throughout the same period, indicating the loss of functional diversity despite increased species diversity. Our analysis also showed that the fish communities shifted from under-dispersion to over-dispersion due to both a decrease in the relative abundance of migratory fish and an increase in the number of fish adapted to the new hydrologic conditions. Our results indicated that the impacts of dams on downstream fish communities may change over time. Interactions between species may become more important when the environment is stable.

Seasonal variations in food resource partitioning among four sympatric gudgeon species in the upper Yangtze River.

Knowledge of food resource partitioning among sympatric fish species is crucial for understanding the potential mechanisms of species coexistence. Gudgeons (Teleostei: Cyprinidae: Gobioninae) often dominate fish assemblages in the upper Yangtze River. However, little research has been conducted on their trophic interactions. In this paper, seasonal diet and feeding strategy variations of four sympatric gudgeon species, Coreius guichenoti, Coreius heterodon, Rhinogobio ventralis, and Rhinogobio cylindricus, were investigated by analysis of intestinal tract contents, aiming to explore whether food resource partitioning occurred among them. Fish specimens were collected during spring (April-May) and autumn (August-October) in 2010 in Hejiang, a free-flowing stretch of the upper Yangtze River. Coreius guichenoti, C. heterodon, and R. cylindricus showed omnivorous feeding habits, while R. ventralis exhibited an obligate carnivore feeding habit. Diet overlap among the four studied species was high, especially in spring. However, changes in feeding strategies were observed in autumn. Specifically, C. guichenoti and R. cylindricus expanded their dietary niche breadth and consumed detritus, Sinopotamidae or Hydropsychidae as important complementary food resources. In contrast, C. heterodon and R. ventralis reduced their dietary niche breadth and became more specialized on mussels (Limnoperna lacustris). These results confirmed that sympatric fish species can coexist with high diet overlap, and food resource partitioning among these species may also fluctuate with the seasons.

Minimum viable population size and population growth rate of freshwater fishes and their relationships with life history traits.

The minimum viable population (MVP) size has been compared for a wide range of organisms in conservation biology, but a limited number of studies investigated it for freshwater fishes, which exhibit diverse life history strategies. In this study, the MVP size and population growth rate of 36 fish species in the Yangtze River were estimated and compared with their life-history traits. The results indicated that the MVP size ranged from 42 to 320 individuals, and instantaneous per-capita population growth rate ranged from 0.009 to 0.188 per year. MVP size and population growth rate were significantly associated with three life history traits: the age at maturity, generation time, and fecundity. Long-lived species with delayed maturation, long generation time, and high fecundity had a greater MVP size and a lower population growth rate than short-lived species. Therefore, our results emphasize a need for prioritizing our conservation effort more on long-lived species.