It has been discovered that low-head dam could impact local habitat conditions, and alter fish assemblages in streams. However, how fish assemblages respond to the size and function of low-head dams is still not clear. Based on the data collected from 15 impounding segments upstream and 15 plunging areas downstream of low-head dams in the Wannan Mountains at July and November 2016, respectively, we examined how habitat factors and fish assemblages varied seasonally, and the differences in their response to dam size and function. Furtherly, after classifying the collected samples into two types (indigenous species and native-invasive species), we determined whether the indigenous fishes and native-invasive fishes were different in their responses to dam disturbance. A total of 24 fish species representing four orders and ten families were collected, including 11 indigenous species and 13 native-invasive species. Although fish assemblages in the plunging areas did not vary seasonally, the assemblages in the impounding areas was significantly different between July and November, where fishes were more abundant in November than in July. Only the assemblage structure of native-invasive fishes in the plunging areas was influenced by dam size. However, both native fish assemblages in the impounding areas and native-invasive fish assemblages in the plunging areas showed difference in their response to the between-dam-function, suggesting that dam function was more important in impacting fish assemblages than dam size. Compared to those associated with the impounding dams, the irrigating dams had less Zacco platypus but more Cobitis sinensis and Ctenogobius spp. in the impounding areas, and more Rhodeus ocellatus and Misgurnus anguillicaudatus in the plunging areas. In addition, the response of the whole fish assemblages (including both indigenous and native-invasive species) to dam disturbance was similar to the indigenous fish assemblages, instead of the native-invasive fish assemblages. Our results suggest that, in this study area, dam function was more important in influencing local fish assemblages than dam size. Due to their potential differences in response to dam disturbance for the indigenous species and native-invasive species, it is necessary for us to distinguish these two types of species when we assess how anthropogenic activities affect fish diversity in streams.
β2-microglobulin plays an important role in the immune system of fish as an essential subunit of MHC class I molecules. We identified 30 SNPs in the β2m gene by directly sequencing method from the parents (P0) of Oreochromis niloticus. The results showed that 1 SNP located in 5′UTR, 17 SNPs located in the exon region (16 synonymous mutations, a synonymous mutation site), 9 SNPs located in the intron region, and 4 SNPs located in the 3′UTR. Snapshot method was used to genotype 102 resistant individuals and 102 susceptible individuals of F1 generation. The genetic parameters such as He, Ho, Ne and PIC of SNPs of β2m gene in Nile tilapia were analyzed with Popgen 32 and PIC-CALC software. The results indicated that 7 SNPs in the susceptible group were moderate polymorphism (0.25<PIC<0.5), and 25 SNPs in the resistant group were moderate polymorphism (0.25<PIC<0.5). In order to reveal its correlation with streptococcal resistant or susceptible traits, the genotype and allele frequencies of 30 SNPs in both resistant and susceptible groups of F1 generation were analyzed by SPSS 23.0 software. These results indicated that 24 SNPs were significantly associated with the streptococcal resistant or susceptible trait (P<0.05). The results of linkage disequilibrium analysis showed that 30 SNPs formed 4 haplotype blocks and 14 haplotypes. 4 haplotypes were significantly associated with streptococcal susceptible trait, and 4 haplotypes were significantly associated with streptococcal resistance trait (P<0.05). Haplotype block 2 and block 3 were two htSNPs inβ2m gene, which contain 4 SNPs and 13 SNPs, respectively, and highly link with each other (r2> 0.9). In this study, the SNPs and haplotypes associated with streptococcal resistant or susceptible traits can be applied to the breeding of streptococcicosis-resistant Nile tilapia as potential markers.
Myxobolus haichengensis Chen, 1958 forms numerous small plasmodia on the gill filaments of wild cyprinid Abbottina rivularis Basilewaky. The species described originally was lacking important characters, which made the accurate identification difficult. Here, we supplemented its characteristics with morphological and molecular data. Plasmodia of M. haichengensis are oval. Mature spores are ellipsoidal-shaped in frontal view and fusiform-shaped in lateral view, measuring (10.8±0.7) μm (10.1—11.5 μm) long, (8.1±0.5) μm (7.5—9.0 μm) wide, and (5.7±0.4) μm (5.2—9.0 μm) thick; two unequal polar capsule are pyriform with tapering anterior, large polar capsule averaging (4.7±0.5) μm (4.8—6.7 μm) long and (2.5±0.2) μm (3.2—4.3 μm) wide; small polar capsule averaging (4.4±0.2) μm (4.1—4.8 μm) long and (2.2±0.1) μm (2.0—2.5 μm) wide; polar filaments coil with four to five turns. The nuclear 18S rDNA sequence was obtained and deposited in GenBank (KY965936), and sequences alignment analyses revealed that M. haichengensis was most similar with the actinosporean Hexactinomyxon type 2 (AY162272, 97%) released from the freshwater tublificid oligochaete Limnodrilus hoffmeisteri.
GPR54 is the cognate receptor of Kisspeptin, which plays a significant role in fish reproduction regulation by acting on the Gonadotropin-Releasing Hormone (GnRH). In order to study the regulation of GnRH by Kisspeptin/GPR54 system in the Dabry’s sturgeon (Acipenser dabryanus), the full-length cDNAs of two gpr54 genes were cloned, which were designated as dsgpr54-1 and dsgpr54-2, encoding 379 and 368 amino acids, respectively. Multiple amino acid sequences alignment and evolutionary tree analysis indicated that Gpr54 of Dabry's sturgeon shared higher sequence identities and closer evolutionary distances with its counterparts in tetrapods. By quantitative real-time PCR, it showed that dsgpr54-1 were transcribed in both gonad (testis and ovary) and brain (hypothalamus, pituitary, mesencephalon and telencephalon) with the highest transcription level in the hypothalamus. Conversely, dsgpr54-2 was only found in the brain, with high expression levels in the pituitary, mesencephalon and hypothalamus. In order to investigate whether gpr54 could regulate the expression of gnrh in the hypothalamus by combined to its ligand Kisspeptin, decapeptides of both Kiss-1 and Kiss-2 (10 nmol/L and 1000 nmol/L) of Dabry's sturgeon were synthesized and injected to the peritoneal cavities of 9 month juveniles. It showed by quantitative real-time PCR that both the two doses of Kiss-1 and Kiss-2 injection induced the increase of gpr54 expression, and 10 nmol/L Kiss-2 injection increased the transcription of dsgpr54-2 significantly (P<0.05). Besides, both two doses of Kiss-1 injection reduced thegnrh expression. However, 10 nmol/L Kiss-2 injection caused the increase of the gnrh1 expression and the decrease of gnrh2 expression, while in the 1000 nmol/L Kiss-2 injection group, gnrh1 expression decreased with no changes of the gnrh2 transcription. The above results revealed that both the two gpr54 genes could bind to its ligands kiss-1 and kiss-2, but with receptor-ligand selection discrepancy. Kiss-1 and Kiss-2 regulate the gnrh expression differently by activating their receptor GPR54 in the hypothalamus of Dabry’s sturgeon.
The enteric microsporidiosis of hatchery-bred juvenile grouper, Epinephelus spp., is the most important in the mariculture area off coast of South China Sea in recent years, however, the taxonomy of the causative agent remains unknown. In this study, histopathological, ultrastructural and molecular evidences were provided to identify the aetiological agent, designated herein as Enterospora epinepheli sp. n.. The intranuclear development of the present species was consistent with Enterospora canceri, the type species of Enterospora genus. The early stages of uninucleate meronts were observed within the infected nuclei, separating from the host nucleus by a simple electron dense membrane. Later, the uninucleate meronts transformed into multinucleate plasmodia (merogonial plasmodia). At this stage, the infected nuclei were hypertrophic, or even ruptured by the multinucleate plasmodia. Sporogonial plasmodia were characterized by the appearance of multiple, small, spherical, membrane-bound vesciles. Then, multiple copies of these membrane-bound vesciles developed into the precursors of the polar filament and anchoring disk of mature spore which surrounded the diplokaryotic nuclei. With the development, sporoblasts separated from the plasmodia by successive division and direct development to mature spores. Mature spores were oval, in direct contact with host nucleus. Spores measured 1.56±0.31 (1.07—1.96) μm in length and 1.08±0.98 (0.93—1.28) μm in width. The spore walls were trilaminar, including an electron dense exospore coat [15.51±0.95 nm (9.87—26.18 nm) thick], surrounding a thick electron lucent endospore [(81.13±2.71) nm (57.16—110.81 nm) thick] and the plasma membrane. The polar filaments were isofilar, coiled with 5—6 turns in two rows. Histopathological analysis clearly revealed that the spores located in the nucleus of goblet cell of the intestinal epithelial and a large amount of spores appeared in the intestinal contents with the shedding necrotic infected enterocytes. Molecular analysis indicated that genetic distances ofEnterospora epinepheli sp. n. form the species of Enterocytozoondiae ranged from 0.162 to 0.225 which was generally out of intraspecies variation. Phylogenetic analysis revealed that the species of Enterocytozoondiae could separate into Clade Ⅰand Clade Ⅱ, and Enterospora epinepheli sp. n. was an independent lineage, clustering with Enterospora hepatopenaei, E. nucleophilia, E. canceri and Enterocyozoon bieneusi within the Clade Ⅱ.
This study investigated the effects of Cd2+ on the biomass, chlorophyll a content, phycoerythrin content and ATP content, the maximum quantum yield of PSII (Fv/Fm), the effective photochemical yield of PSII (YII), the relative electron transfer rate (ETR) and non-photochemical fluorescence of quenching (NPQ) of the Porphyridium purpureum. The results showed that the growth rate of P. purpureum decreased significantly by the stress of Cd2+ in a dosage-dependent pattern. The content of chlorophyll a, phycoerythrin and ATP decreased significantly by Cd2+ stress with a dose-dependent way. The chlorophyll fluorescence parameters (Fv/Fm, YII and ETR) under Cd2+ stress were significantly lower than those of the control groups and decreased rapidly with increased Cd2+ concentration. NPQ value increased significantly at low Cd2+ (<200 μmol/L) and decreased significantly at high Cd2+ (>500 μmol/L). Therefore, the gorwth and phtochemical activities ofPorphyridium purpureum would be significantly affected by the concentration of the Cd2+ above 5 μmol/L and the accumulation of Cd2+ would have an impact on the ecological balance of the Porphyridium purpureum in aquatic environment.
One of the serious problems in aqua-cultural yellow catfish is that the background of female parents is confused. It is particularly important to establish all-female families for the all-male and hybrid yellow catfish production, in which sex-reversal of XX female to XX male is a key step. Development of sex chromosome-linked markers provides a technical support for the identification of XX males in yellow catfish. In this study, different concentrations of 17α-methyltestosterone (MT) and aromatase inhibitor letrozole (LZ) were used for 54 days to treat yellow catfish (7 to 60 days post fertilization). The survival rate, body length, and body weight of each group were measured at 61 days after fertilization (61 days post fertilization). Gonadal structure was observed and histologically analyzed in XX individuals that were identified by sex-linked markers. As a result, MT and LZ treatments had no significant effects on the survival rate when compared with the control group. In addition, the XX gonad treated by MT showed seminal vesicles and could not be reversed into functional testis. However, appropriate dose of LZ could induce the sex-reversal of XX female to normal XX male, and the induction effect was enhanced with the increase of dose as well. The XX male could normally mate with XX female and YY female, which demonstrated appropriate reproductive ability. The present study proposed a reliable method to create XX male using the aromatase inhibitor LZ, which lays the foundation for the breed improvement of all-male yellow catfish and cultivation of new varieties of yellow catfish.
In this research, the effects of different concentrations of melatonin (MLT) on the growth, accumulation of astaxanthin, reactive oxygen species (ROS), signal molecules, and the expression of DXS were studied in Haematococcus pluvialis LUGU under abiotic stress conditions (e.g., high light, nitrogen starvation, etc.). The results showed that the astaxanthin content was efficiently enhanced in alga cells treated with 10 μmol/L of MLT, the maximum astaxanthin content achieved was 31.32 mg/g, being 2.36 times higher than that of the control. In addition, MLT inhibited intracellular ROS levels and up-regulated the content of signaling molecules (nitric oxide and salicylic acid). Additionally, the relative expression level of DXS gene was increased by 11.3-fold higher than that of control. These results demonstrated that the massive accumulation of astaxanthin in Haematococcus pluvialis is associated with the regulation of intracellular ROS, signaling molecules, and gene expression by exogenous MLT under abiotic stress conditions.
A 42-day feeding trial was conducted to investigate the effects of α-ketoglutarate (α-KG) on gill Na+/K+-ATPase activity and blood biochemical parameters of grass carp, Ctenopharyngodon idellus, exposure to ammonia. A total of 270 individuals [initial body weight: (24.79±0.11) g] were randomly assigned to 9 tanks, and these tanks were divided into three groups (Ⅰ: treated with 1.51 mg/L of aerated water and basal diet; Ⅱ: treated with 18.37 mg/L of ammonia solution and basal diet; Ⅲ: treated with 18.37 mg/L of ammonia solution and 0.75% α-KG added diet), with three replicates per each group (n=30). Experimental fish were sampled on 1st, 14th, 28th, and 42 days, respectively. The results showed that: (1) diet α-KG could effectively alleviate a significant increase in the content of plasma ammonia on the 1st day, the activity of plasma aspartate transaminase on 14th day and plasma alkaline phosphatase on 28th day, which were caused as being exposure to ammonia; diet α-KG could effectively alleviate a significant decrease in the activity of gill Na+/K+-ATPase on 28th day, plasma alanine aminotransferase on 28th and 42th days, and the content of plasma urea on 28th day because of being exposure to ammonia. Diet α-KG could significantly increase plasma globulin content on 28th day exposure to ammonia. In conclusion, dietary α-KG could alleviate the increase of plasma ammonia content exposure to ammonia, and maintain the stabilization in the activity of gill Na+/K+-ATPase, plasma alanine transaminase (ALT), plasma aspartate aminotransferase (AST), plasma alkaline phosphatase (ALP), and the content of GLB, as well as urea in grass carp exposure to ammonia.
The ecological risk of a Microcystis bloom was evaluated on the basis of the ecotoxicological risk assessment method. The effects of Microcystis bloom on benthic fauna, zooplankton, fish, and submerged macrophytes were assessed by using acute and chronic exposures experiments and the findings reported by previous studies. The algal cell densities were calculated by using toxicity percentile rank (TPR) method, and aquatic ecological risk assessment for Microcystis bloom was performed by using risk quotient approach. The criteria required for acute and chronic ecological risk assessment of Microcystis bloom were defined based on the algal cell density, algal bloom coverage in lake, as well as duration of algae blooms. The acute ecological risk was classified as low-, moderate-, and high- levels. A Microcystis bloom with cell density less than 3.4×106 cells/L was defined as low risk-level, with cell density at the range of 3.4×106—3.4×107 cells/L was denoted as moderate-risk level, and with cell density higher than 3.4×107 cells/L was defined as high-risk level. Similarly, chronic ecological risk of Microcystis bloom was also classified as low-, moderate-, and high-levels of risk. The Microcystis bloom with cell density less than 1.1×106 cells/L was classified as low risk, cell density between 1.1×106—1.1×107 cells/L was classified as moderate risk, and the cell density greater than 1.1×107 cells/L was classified as high risk. In practical applications, cell density, algal bloom coverage, and duration of algal blooms are essential factors to formulate a robust ecological risk assessment strategy for Microcystis bloom in Erhai Lake. In presence of moderate-risk level, early warning of Microcystis bloom should be alarmed, and improvement of water quality or implementation of biological control should be carried out. Under the high risk level, emergent removal or control of algal bloom should be undertaken as well.
In order to explore a proper bait of larva and adult fish Gobiocypris rarus, we randomly divided hatchetfish, 35 day after hatching, into five groups: Group A was fed with Artemia nauplii; Group B was fed with A. nauplii for 6 days, and was fed with commercial micro pellet diet for 1 day per week; Group C was fed with A. nauplii for half a week, and was fed with artificial diet for another half a week; Group D group was fed with A. nauplii for 1 day per week, and was fed with artificial diet for 6 days per week; Group E was fed the artificial diet. Each group was fed with a feeding satiation strategy. Each 2 weeks, growth and survival indicators were counted until 21st week (147th day). Reproductive capacity and offspring abnormal rate were calculated after spawning. The gonads obtained in 17th week (119th day) were used for histological studies. The results showed that: (1) In group E group, survival and specific growth rates were significantly lower than other groups (P < 0.05); (2) reproductive capacity of group B was significantly higher than other groups ( P < 0.05); (3) different feeding strategies had no significant effect on testis maturity, while had influence on ovarian maturation. The results of this study suggest that addition of A. nauplii contains superior results than single feeding with commercial micro pellet diet, which was more conducive to the growth and reproduction of G. rarus. We suggested that optimal feeding ratio for A. nauplii and commercial micro pellet diet is 6:1, that would be more appropriate for larvae and juvenile G. rarus in the process of standardized cultivation.
In 2017, to further confirm the speculation and epidemiological traits of carp edema virus (CEV), 26 carp farms in 5 provinces of north China, where " acute rot gills disease of carp”, were occurred, surveyed, and sampled. CEV and koi herpes virus (KHV) were detected using quantitative polymerase chain reaction (qPCR) and nested PCR techniques. In addition, 97 carp farms in 9 provinces of China were randomly surveyed for CEV and PCR products for sequencing and analyzing viral DNA of CEV. The results showed that 20 farms were CEV-positive samples, 1 farm was KHV-positive sample, and 1 farm was infected by Sporozoa among 26 farms in north China. Besides, 50 farms were CEV-positive samples among 97 randomly surveyed farms, and infected strains belonged to genogroup II (GII). CEV was detected in different study regions, temperature of water, size of fish, and species of carp with high rate of infection, and there were no significant differences between them. In summary, CEV infection was found to be the major cause of " acute gill-rot disease of carp” in several provinces, and showed high-rate of positive detection in carp farms in north of China. In addition, CEV infection affected various species of common carps including koi carp with different sizes at the temperature range of 12—27℃.
Coreius guichenoti (Sauvage & Dabry de Thiersant, 1874) is an endemic and commercially important fish in the upper Yangtze River, and its spawning grounds are mainly distributed in the main stem of the middle and lower reaches of the Jinsha River (which belong to the upper streams of the upper Yangtze River) and its tributary, the Yalong River. However, due to dam cascade in the Jinsha River and Yalong River, the spawning and feeding habitats of C. guichenoti have changed dramatically, leading to a significant decline in the population of endemic fish over last decade. To protect the fish resource ofC. guichenoti, many protective plans, including captive breeding, have been designed and implemented. It is very important to study their reproductive biology to provide basic information for captive breeding. Thus, based on the parent fish of C. guichenoti collected at the Jiaopingdu spawning ground from 2013 to 2014, and at the Jinanqiao-Qiaojia river located in the middle and lower reaches of the Jinsha River from 2006 to 2014, the reproductive biology of C. guichenoti was studied. The results showed that the minimum total length, weight, and age of mature females were 330 mm, 441 g and 4 years, respectively, while those for the mature males were 352 mm, 396.6 g and 3 years, respectively. The age and total length at which 50% of the individuals reached sexual maturity were 4.32 years and 406 mm for females, and 4.44 years and 412 mm for males, respectively. The sex ratio between male and female in the Jiaopingdu spawning ground was 1.37﹕1, which was not significantly different from 1﹕1, and the age structure of sexually mature individuals were 4—7 years in female and 3—7 years in male. The mean gonadosomatic index (GSI) displayed the highest value of 10.55% for female and 3.45% for male in 6-year-old for both genders. The average egg diameter ofC. guichenoti was 0.16 cm, and the egg diameter distribution displayed two groups of ooctes within the same ovary. The absolute fecundity of mature female varied from 4055 to 137900 eggs with an average of 22817 eggs, while the relative fecundity ranged from 5 to 73 eggs per gram with an average of 20 eggs per gram. Moreover, the absolute fecundities for the 75.68% individuals were between 10000 eggs and 30000 eggs, while the relative fecundities for the 70.27% individuals were between 15 and 20 eggs per gram. The absolute and relative fecundities of mature female increased with the total length and body weight, and the relationships between the total length and body weight and the absolute fecundity or relative fecundity could be represented by an exponential function (absolute fecundity) or quadratic function (relative fecundity). The research results can provide important basic data support for the protection of C. guichenoti fish resources in the Yangtze River Basin.
Purifying wastewater with biological methods is highly important in the field of ecological recirculating aquaculture. To study the effects of temperature on the absorption of nitrogen and phosphorus and photosynthetic performance of macroalgae in sea water, four species including Ulva fasciata, Ulva intestinalis, Gracilaria lemaneaformis and Pyropia haitanensis were cultured under four temperature conditions (15, 20, 25 and 30℃). The results showed that: (1) most N and P had been absorbed by the four macroalgae species, and the absorbing ability from high to low is Ulva intestinalis>Ulva fasciata>Pyropia haitanensis>Gracilaria lemaneaformis; (2) extremely high and low temperature will limit the absorbing of N and P, growth, relative electron transfer rate, and chlorophyll fluorescence in four macroalgae species; (3) U. fasciata and U. intestinalis were the best choices due to their high absorption rates of N and P and the tolerance of a wide temperature range; (4) nitrogen and phosphorus could be completely absorbed within 48h by the four macroalgae species. To promote algal growth, improve the removal efficiency of nutrients, as well as prevent secondary pollution caused by nutrition limited negative growth of macroalgae, it’s better to replace the wastewater within 24—48h, or apply the circulation mode in the process of wastewater treatment.
Tintinnids are the best known group of marine ciliates and recognized as indicator species of different water masses due to their hard loricae. In the present study, a number of tintinnid species were identified based on samples obtained at six representative sites located in the Bay of Amoy from May 2015 to March 2016. Samples were collected from surface water, concentrated using 20 μm mesh, fixed by ethanol (>80% final concentration), and then stored at dark and cool conditions for further analysis. Tintinnids were isolated under a stereomicroscope and the morphological characteristics of lorica were examined under compound light microscope and documented using a charge-coupled device (CCD) camera. Totally, 27 species were identified includingTintinnopsis (20 species), Favella (1 species), Stenosemella (1 species), Codonellopsis (2 species), and Leprotintinnus (3 species), respectively. Besides, Tintinnopsis ventricosoides species (Meunier, 1910) was believed as the first record in China. Based on their lorica features, all species were here detailed.
The epidemiological investigation, symptom observation, pathogenic detection, and the pathology detection were used to examine the cause of the disease of Sciaenop socellatus of cultured pond in Zhuhai, Guangdong Province from June to October. These results showed that the disease had obvious infectious. The anatomy examination revealed the anemia of the gill filament, swollen spleen and kidney with hemorrhagic spots, and no observed large number of parasites by microscopy. Meanwhile, no pathogenic bacteria were isolated from the liver, spleen, kidney and intestine of the diseased fish. A large number of swelling cells were observed in pathological sections of liver, spleen and kidney of diseased fish. The 570 bp fragment was amplified by PCR using the specific primers of OIE. MCP sequence alignment showed that the amplification of the gene sequence had 99.2% of homology with gene sequence of RSIV. The comprehensive results showed that the cause of the disease of the Sciaenop socellatus is infected by the iridovirus of Megalocytivirus genus.
This study investigated cell ultrastructure of Rhopilema esculentum during embryogesis and metamorphosis into a polyp using scanning and transmission electron microscopy combined with protargol staining method. Our study showed that (1) Cell cleavage was almost equal from fertilized egg to gastrula. All divided cells were similar in morphology, and cell junctions were observed among adjacent cells; (2) Vacuoles in cell were firstly observed at ectoderm of early planula, and became bigger as developing to 4-tentacle polyp, while the vacuoles of entoderm were firstly found at 4-tentacle polyp stage. The suspected apoptotic body were observed at scyphostoma and polyp stages; (3) Immature cnidocytes were firstly observed in ectodermal area closed to mesoglea ectoderm at early planula stage, moved to outside, located at outermost layer, and matured at polyp stage; (4) Cilium was observed at early planula stage, gradually degraded, and completely disappeared at polyp stage; (5) Lots of yolk bodies with dark stain were observed at all developmental stages, and the phagocytosis of ectodermal cell of planula was firstly observed. These phenomena suggest that planulae of R. esculentum were both planktotrophic and lecithotrophic, which would provide the scientific basis for illuminating the developmental pattern of embryonic and metamorphosis of cnidarians.
In order to investigate the diversity of Pseudo-nitzschia species in China’s coast and their ability in producing neurotoxin domoic acid (DA), a total of fifteen monoclonal Pseudo-nitzschia strains were isolated and established. Using a liquid chromatography tandem-mass spectrometry (LC-MS/MS) technique, DA was accordingly detected from ten monoclonal strains. Based on the morphology observed by using a light microscope (LM), a transmission electron microscope (TEM), as well as molecular analysis inferred from an internal transcribed spacer region, these fifteen strains were precisely identified which belonged to three different species involving, P. cuspidata (Hasle) Hasle, P. pseudodelicatissima (Hasle) Hasle, and P. fraudulenta(Cleve) Hasle. In addition, three out of eleven established P. cuspidata strains were nontoxic, while other eight cases were toxic with the DA abundance rate of 0.4—5.5 fg/cell. Also, one P. pseudodelicatissima strain was nontoxic, while DA production rate of 1 fg/cell was detected in another strain. Besides, no DA was tested in the two P. fraudulenta strains. Several strains were selected and their DA productions were induced by the available Artemia salina. As a result, it was shown that the ability of DA production decreased in P. cuspidate (MC4049) and P. pseudodelicatissima (MC3015) strains, from 2 and 1 to 0.2 and 0.4 fg/cell, respectively. However, the ability of DA production in P. fraudulenta(MC4074) strain swiftly increased, from an undetected level to 17.5 fg/cell. The results achieved in this study enrich the diversity of toxic Pseudo-nitzschiaspecies in China’s coast, and may establish strong research basis for conducting further studies.
This study attempted to theoretically support and comprehensively perceive genetic diversity and reproduction of Corbicula fluminea from the Laodao River in Liuyang city was investigated. Partial sequences of the cytochrome oxidase c subunit 1 (COⅠ) of mitochondrial genes were utilized to evaluate the genetic diversity, and reproductive characteristics were observed by gonadal histology and sperm morphology using light microscopy. Among examined 40 individuals, only 4 haplotypes and 17 variable sites were detected in the partial sequences of the COⅠ, with an average haplotype diversity, nucleotide diversity, and number of variable sites equal to 0.664±0.042, 0.014±0.006, and 8.595, respectively. Hermaphrodite was a predominant reproduction in the population studied, and the hybrid hermaphrodite-sex ratio was 6﹕3﹕1. Furthermore, there were two types of reproductive follicles in hermaphroditic individuals, including sperm and egg cells in the same and in different follicular cells. The observation of sperm morphology revealed that biflagellate spermatozoa were discovered in both hermaphrodite (n=23) and male (n=8) cases. The results also showed that Corbicula fluminea samples from the Laodao River of Liuyang city contained a relatively low genetic diversity, but with multiple reproduction modes, and the predominant mode was androgenesis. This study attempted to present significant biological reproduction information required for Corbicula fluminea protection in China.
The fermented soybean meal (FSM) was used as a replacement of fish meal (FM) in a practical diet with 45% protein and 10% lipid, to investigate its effects on the growth, intestinal histology, and the structure of intestinal dominant bacteria in juvenile large yellow croaker. FM was replaced by 0, 15%, 30%, 45%, 60% and 75% of FSM (FSM0, FSM15, FSM30, FSM45, FSM60 and FSM75), respectively. The fish of 10.49 ± 0.03 g was hand-fed daily to satiation twice for 56 days. Results showed that survival was not significantly affected with all the diets (P>0.05), but in groups FSM60 and FSM75, theSR had a downward trend. In comparison with FM0, the weight gain rate (WGR) and specific growth rate (SGR) in FSM60 and FSM75 groups decreased significantly (P<0.05), while the feed conversion rate (FCR) increased significantly (P<0.05). Feed intake (FI) increased significantly in FSM60 and FSM75 groups (P<0.05), compared with that in FSM0, FSM15, FSM30 and FSM45 groups. The observed intestinal histology results showed that Mucosa thickness, Mucosafold height, Laminapropria width and Gobletcell quantity were not significantly affected in all the diets (P>0.05). Sequencing results of intestinal contents from Illumina-MiSeq high-throughput sequencing technology showed that the index of Chao1, Shannon, Simpson and Good coverage in FSM0 (TC the control), FSM45 (TB the best group in growth) and FSM75 (TW the worst group in growth) were not significantly affected (P>0.05).Firmicutes group totally dominated the bacterial communities in juvenile large yellow croaker. Paenibacillus genus was the most dominant bacteria in microbial ecosystem. Bacterial composition had certain effect on the growth of large yellow croaker: compared with TW group, the species richness of Paenibacillus and Alkaliphilus increased significantly in TB group and TC group (P<0.05). However, compared with TW group, the species richness ofEnhydrobacter in TB and Paracoccus in TC decreased significantly (P<0.05). These results suggested that the optimal dietary protein level was about 45% without negtive effects on the growth, intestinal histology, and the structure of intestinal dominant bacteria in juvenile large yellow croaker.
The present study aimed to examine the genetic diversity and genetic structure of the successive selective breeding populations of Cyprinus carpio rubrofuscus from F1 to F4 generations by using 16 microsatellite markers. The results showed that 99 alleles were detected among 16 polymorphic microsatellite loci. The number of alleles detected on each locus varied from 3 to 10, and the average number of alleles was 6.1875. From F1 to F4 generations, the average number of alleles for 16 microsatellite markers decreased from 5.6875 to 4.6755, the average of heterozygosity ranged from 0.7943 to 0.7135, and the average of polymorphism information content (PIC) reduced from 0.6577 to 0.5834, respectively. The genetic distance between F1 and its descendant generations (F2-F4) increased from 0.1486 to 0.2181, while the genetic identity decreased from 0.8619 to 0.8041. The values of genetic differentiation index (Fst) between the adjacent generations decreased (0.062 between F1-F2; 0.058 between F2-F3; and 0.051 between F3-F4), whereas the values of genetic identity increased. Pairwise values of Fst ranged from 0.05 to 0.15, reflecting that the selective breeding populations contained moderate genetic differentiation among four generations and the genetic structure has been varied from one generation to the next one through selective breeding. This study suggested that the selective breeding was an efficient approach, and there was a decrease in genetic heterozygosity and genetic diversity, while high genetic diversity and genetic potential were maintained in the selective breeding populations, indicating that there is a great potential for future selections of Cyprinus carpio rubrofuscus through selective breeding. Our study provides precious information for genetically breeding in Cyprinus carpio rubrofuscus as well.
In the present study, the effects of isoleucine on the mammalian target of rapamycin signaling (mTOR) pathway and nitrogen metabolism were investigated through Intraventricular (ICV) administration in Chinese perch (Siniperca chuatsi). In one hand, the ammonia excretion significantly increased, and mRNA levels of nitrogen metabolism genes involving glutamate dehydrogenase (GDH), glutamic oxaloacetic transaminase (GOT), and adenosine monophosphate deaminase (AMPD) remarkably increased after ICV injection of isoleucine as well (P<0.05). On the other hand, the results showed that blood glucose levels markedly decreased at 0.5h post-injection. The expression of liver ribosomal protein S6 was also notably enhanced, demonstrating that mTOR signaling pathway was activated. The results also indicated that isoleucine could activate the mTOR signaling pathway, mediate amino acid metabolism, and enhance ammonia-N excretion via nitrogen metabolism genes in Chinese perch.
In this study, the method of irradiation breeding was applied to wetland plants in order to improve its cold resistance. Herein, 25, 45, 60 and 80 Gy doses of gamma ray were used to irradiate Canna indica Linn (CIL) seeds, and the dose rate was 6 Gy/min. After CIL seeds were grown up, they were exposed to a low temperature stage, and their cold hardiness was accordingly evaluated. The results showed that the activity of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) in irradiated CIL seeds were higher than that of the control group. Malondialdehyde (MDA) in control group accumulated in large quantities under low temperature, which was higher than that of the irradiation treatment group. Besides, at low temperature, the content of proline, the total soluble sugar, and protein of irradiated seedlings were totally higher than that of the control group. The score of cold resistance in irradiated group was also higher than that of the control group, and the 45 Gy dose of gamma ray group showed the highest score. Moreover, CIL with the strongest cold resistance was planted in the constructed wetland to evaluate its purification effect in winter, and evaluation indexes were total phosphorus (TP), total nitrogen (TN), and chemical oxygen demand (COD). Results revealed that the removal rate of TP in the group of CIL in constructed wetland by using 45 Gy dose of gamma ray was significantly higher than that of the control group (P<0.05). It can be concluded that irradiation treatment can effectively improve the cold resistance ofCIL and enhance the effect of artificial wetland purification in winter.
In order to provide basic information for protecting and rational utilizing resources of the Yangtze Estuary, feeding types, trophic level, energy flow, and food web, 43 aquatic animals were studied by using stomach content analysis. The species were classified into four groups according to their feeding habit: plankton feeding, benthic feeding, nekton feeding, and mixed feeding (benthic and nekton feeding). Among the samples collected in this study, the plankton predators were dominant accountings for 39.53%, and the nekton predators had the minimum dominancy, accounting for 11.63%. The results of trophic level showed that according to the dietary habits, these aquatic animals can be also divided into 3 different groups, which herbivorous consumers were dominant, and accounted for 76.75%, while intermediate carnivorous fish had the minimum dominancy, accounting for 4.65%. Through the overfishing and environmental degradation, the trophic levels of the 12 common fish in the Yangtze Estuar were generally lower than those of the 1990s, the average trophic level dropped from 3.80 to 2.87. According to each consumer’s stomach content, this study determined the benthic algae and phytoplankton, and organic detritus, including particulate organic matter (POM), as the main producers of the Yangtze Estuar aquatic food web, and drew their own energy flow. Eventually, based on the nutritional relationship among different aquatic animals, this study proposed a simplified model for the Yangtze Estuar aquatic animals’ food web.
To investigate the effects of exhaustive chasing training on parameters of respiratory and circulatory system and excess post-exercise oxygen consumption (EPOC) in juvenile qingbo (Spinibarbus sinensis) and rock carp (Procypris rabaudi), sixty samples of S. sinensis (28.36±0.08) g and sixty samples of P. rabaudi (19.53±0.13) g were randomly divided (equally 30 fish in each group) into control group and training group, respectively. Then, these fish in the training group were analyzed under exhaustive chasing training once per day for 3 weeks at 25℃ to measure the heart index, gill index, hematological parameters, and EPOC. The results showed that there were no significant differences in the heart index, gill index, hemoglobin content, and number of red cells between the control group and training group of S. sinensis and Procypris rabaudi(P<0.05). The gill index in the control group ofP. rabaudi was significantly lower than that in the control group of S. sinensis(P>0.05), whereas the heart index, hemoglobin content, and number of red cells in the control group ofP. rabaudi were not significantly different than that in the control group of S. sinensis(P<0.05). No significant differences were found in pre-exercise metabolic rate, peak post-exercise metabolic rate, factorial metabolic scope, and recovery rate between the control group and training group (P>0.05), whereas duration of EPOC in the training group was significantly higher than that in the control group ofS. sinensis (P<0.05). The pre-exercise metabolic rate in the control group was significantly lower than that in the training group (P<0.05), whereas peak post-exercise metabolic rate and factorial metabolic scope, duration of EPOC, and recovery rate in the control group were not significantly different than that in the training group ofP. rabaudi(P>0.05). The pre-exercise metabolic rate, peak post-exercise metabolic rate, EPOC magnitude, and recovery rate in the control group ofP. rabaudi were significantly lower than that in the control group of S. sinensis(P<0.05), whereas factorial metabolic scope and duration of EPOC in the control group ofP. rabaudi were not significantly different than that in the control group of S. sinensis(P>0.05). Our results suggested that (1) exhaustive chasing training had no significant effects on the parameters of respiratory and circulatory system ofS. sinensisandP. rabaudi(P>0.05); (2) exhaustive chasing training significantly increased anaerobic capacity ofS. sinensis(P<0.05); and (3) the pre-exercise metabolic rate and peak post-exercise metabolic rate ofS. sinensis were significantly higher than those of P. rabaudi(P<0.05), which may be related to active habits ofS. sinensis.
In order to provide biological information for research on sex-determination mechanism in Pelodiscus sinensis, we here first attempted to clone and analyze the partial-length of Foxl2 cDNA. In addition, to address the differential expression of Foxl2 at genetic and physiological levels, both male and female sexes of Pelodiscus sinensis were treated with 10 mg/kg E2 and 17α-methyltestosterone (MT), respectively; Foxl2 mRNA expression was quantitatively examined in the gonads after injection treatment at 6, 12, 24, and 48h, as well as 7 and 14d, respectively. Foxl2 (GenBank Accession No.KP734210) was achieved, belonging to Forkhead family of transcription factors that is involved in ovarian development and functional maintenance, as well as a 903 bp of open reading frame (ORF) encoding 300 amino acids. Multiple sequence alignment showed that Foxl2 contained typical FH-domain, and the most similar ortholog was Trachemys scripta, reaching up to 99%. Stability analysis of phylogenetic trees showed that Pelodiscus sinensis Foxl2 was clustered with reptile Foxl2 as a sub-branch, and was closely associated with Foxl2 from Chrysemys picta bellii. Results of quantitative reverse transcription PCR (RT-qPCR) indicated that, compared to the control group, E2 significantly up-regulated Foxl2 mRNA repression in ovary after 24h (P<0.001), which in testis was significantly increased after 7 and 14d (P<0.001). MT treatment strongly and equally up-regulated expression levels ofFoxl2 mRNA in ovary and testis at 24h (P<0.001). These results suggested that E2 and MT could up-regulate Foxl2 expression. Moreover, the sex differences in E2 promoting Foxl2 expression is more significant than MT. It can be concluded that the present research contributes to better understanding of the functional role of Foxl2 and provide basic data for further study on how exogenous hormone mediates Foxl2 in Pelodiscus sinensis.
There is limited information available on effects of aquaculture on lake ecosystems. Community structure and biodiversity of phytoplankton were investigated from July to September, 2015 in 23 lakes in the middle reach of the Yangtze River Basin, which include four groups: reservoir group (A), aquaculture ban group (B), low stocking aquaculture group (C) and high stocking aquaculture group (D). The analysis showed that dominant genera of the four groups were different. Group A was dominated by Pseudanabaena (Y=0.642) and Planktolyngbya (Y=0.064). Group B was dominated by Merismopedia (Y=0.428), Planktolyngbya (Y=0.118), Pseudanabaena (Y=0.133), and Scenedesmus (Y=0.066). Group C was dominated by Pseudanabaena (Y=0.395), Merismopedia (Y=0.097), and Planktolyngbya (Y=0.122). Group D was dominated by Merismopedia (Y=0.308), Microcystis (Y=0.118), and Pseudanabaena (Y=0.077). The phytoplankton abundance in group A was significantly lower than those in other lake groups (P<0.05). There was no significant difference in Shannon-Wiener index, Margalef index and Pielou index of phytoplankton among the four lake groups. The study indicated that fish culture could affect the abundance and dominant genera of phytoplankton, which may provide some implications for lake ecosystem management.
The histology of gonadal development in Ptychobarbus dipogon was studied by using conventional paraffin sections and HE staining, in order to obtain information on its reproductive systems useful for its artificial breeding. The results showed that the development of oocytes can be divided into five phases, and ovarian development can be divided into six stages. In stage V ovaries, ovum worship was found to occur, indicated by the 1.38:1 ratio of small ova to large ova. Phase 3 oocytes were characterized by appearance of yolk granules and follicles; phase 4 oocytes by rapid increase of yolk granules, and the movement of the nucleus toward the animal poles; phase 5 by the fusion of yolk granules, and the separation of oocytes from follicular membranes to float in the ovarian cavity. Male P. dipogen had lobular testes, and their germ cells can be categorized into spermatogonia, spermatocytes; spermatids; and spermatozoa. Their testes also developed in six stages. The species followed a batch-synchronous spawning pattern.
Knowledge of the vulnerability of different species and size groups to various types of fishing methods is vital to the development of optimal harvesting strategies and rational exploitation of fish resources. In this study, the selectivity of four types of fishing methods (weir nets, gill nets, electrofishing, and cormorants) used simultaneously in a typical multi-species shallow lake (Lake Niushan, China) within the Yangtze River basin, was compared for catch composition, efficiency, and size selection. Species selectivity was evaluated with the index of relative importance (IRI). Potential fishing effects on the trophic structure of fish community were analyzed by calculating the mean trophic level (MTL) of the catches and the weight ratio between prey and predator fishes. Results indicated the use of weir nets and electrofishing should be reduced or eliminated, because they were relatively unselective and caught many species, including juvenile individuals. Fishing efforts of cormorants should be restricted due to their high fishing efficiency, especially on piscivorous fishes. Gill nets with appropriate mesh size are likely to be a more sustainable fishing method since they were more selective in capturing larger individuals and could balance the prey-predator relationship. We suggest shifting from single-species approaches toward multi-species management, and taking trophic interactions into account to better manage fishery resources.
The yellow perch, Perca flavescens, is an economically significant freshwater fish species in the Midwest of the United States. TypeⅠ markers are useful for comparative mapping and other genetic analyses, but limited quantities in yellow perch. In the present study, EST containing microsatellite sequences were identified and characterized for yellow perch by data mining from updated public EST databases. Out of 21,968 EST sequences of yellow perch, about 14.4% of ESTs contain repeat motifs of various types and length. CA repeat was the most abundant dinucleotides. Out of the 62 EST-SSRs for which PCR primers were designed, 15 loci showed polymorphic in a yellow perch population with the alleles per locus ranging from 4 to 19 (average 9). The observed (HO) and expected (HE) heterozygosity of these EST-SSRs were 0.103—0.929 and 0.116—0.934, respectively. Four EST-SSR loci significantly deviated from the Hardy-Weinberg equilibrium (HWE) expectation, and the remaining 11 loci were in HWE. These new EST-SSR markers should provide sufficient polymorphism for population genetic studies and genomic mapping of yellow perch.
To assess possible bias of different fishing methods is essential to appropriate fisheries management. In the current study, fish assemblage structure of a shallow Yangtze River lake was assessed by combining one international standard sampling gear (multi-mesh gillnet), and one traditional Chinese gear (the dense-mesh weir). Using Lake Biandantang as a case study, a total of 27 fish species were collected from the two gears combined, including 2 new species that had not been recorded previously in this lake. Results suggested that fish assemblages had changed greatly compared to a previous study conducted in the 1990s. Specifically, differences were found in species composition, abundance, biomass, and length distributions collected from the two gears. Difference in total length (TL) distributions of fishes caught was the most conspicuous change. Fishes collected from the weir ranged from 40—70 mm TL, whereas fishes collected from gillnets ranged from 90—140 mm TL. Multivariate ordinations based on relative abundance and biomass data also indicated fish assemblage structural differences between the two gears. The comparative results showed that the multi-mesh gillnet was effective at assessing fish assemblages in shallow lakes, such as those found along the middle and lower reaches of the Yangtze River. Additionally, assessments using only one gear could have some limitations with respect to interpreting fish assemblage changes over time.
Asian carp are expanding their range throughout the Mississippi River; however, abundance is thought to be highest in reaches within close proximity to the Illinois River. In the Mississippi River, Lock and Dam 19 (L&D 19) at Keokuk, Iowa is the primary barrier to slow the expansion upstream. As Asian carp abundance increases below L&D 19, it is important to investigate potential means of control (i.e., reduction through harvest and barriers) that will prevent complete invasion of the Mississippi River above L&D 19. Silver Carp and Bighead Carp were collected below L&D 19, a subsample were implanted with ultrasonic transmitters to evaluate passage through the lock chamber and the remainder were used to determine population dynamics at the leading edge of invasion. Although the dam portion of the structure poses a complete barrier to upstream expansion, we documented lock chamber passage demonstrating the lock chamber has the capability to provide passage upstream. Based on the results of the population assessment, in order to induce recruitment overfishing at this leading edge of invasion, Asian carp will need to be intensively harvested at 300 mm and larger. The combination of commercial fishing efforts and research investigating ways to prevent passage upstream must be employed.
Our study examined spatial distribution differences of rotifer resting eggs (RRE) in lakes of the Poyang Lake Wetland Area during dry season, January 2015. Field sampling was conducted in both Nanshen Lake and Baisha Lake. We found that densities of RRE in different habitats were significantly different (P<0.05), and their distribution had an obvious gradient. The highest mean density was in the marshland vegetation area of Nanshen Lake, where it was (3.34±1.28) ind./cm3. The density of resting eggs in the Zizania latifolia area was up to 5.45 ind./cm3. The density of RRE was different spatially, with the greatest in the vegetation area, then in the muddy area, and then the lowest in the water area. ANOVAs results showed that water depth, vegetation, and sediment had significant effects on RRE (P=0.001, 0.007, <0.001, respectively). The trend of resting egg densities in different aquatic habitats was: emergent aquatic plant > marshland vegetation > floating-leaf plants > submerged plants. The distribution of RRE in areas of different water depths was inconsistent. The density of RRE was higher in the hard than soft sediment.
Sexual dimorphism refers to the morphological differentiation between males and females in the same population, such as sizes, morphological features, and colors. Cold water fish Glyptosternum maculatum, is an endemic teleost species of notable economic importance and with high potential for controlled rearing of the species in Tibet Autonomous Region. In this study, morphological measurements and related analysis were conducted on sexually mature G. maculatum to investigate their morphological differences in Tibet Autonomous Region. Results indicated the sexually mature populations indeed display really displayed significant sexual dimorphism: males exhibited significantly greater body length, weight, and males also exhibited in addition to greater tail length while females exhibited significantly greater eye diameter, body depth, trunk length, and lengths of dorsal, pectoral, pelvic, anal, and caudal fins at a given body length. Principal components analysis on 16 morphological parameters showed that the differences were largely due to features of the body shape (including lengths of body parts and fins) and the head, and differences in the above features differences contributed 76.7%. The t-statistic test on the allometry index b in the total length-weight function showed that during the breeding season, the total lengths and weights of G. maculatum females developed proportionally, while the male specimens were allometrical.
Silver carp Hypophthalmichthys molitrix were introduced into the U.S. to control water quality in aquaculture ponds. From this point of origin, silver carp escaped into nearby rivers through multiple flood events. Because of their documented negative effects on native biota, silver carp have been labeled as problematic. Therefore, evaluating the biology and ecology of these non-indigenous species is critical. Multiple parameters are needed to evaluate silver carp populations (length, weight, age, and sex). Furthermore, developing methods for rapidly acquiring these data are needed. In relation to sex determination, sexual dimorphism was observed where males exhibit distinct pectoral fin ray features. Specifically, males have pronounced ridges or a " rough patch” on the dorsal surface of pectoral fins. Therefore, to test if this was an applicable way of determining silver carp gender; silver carp were collected from Midwestern U.S. rivers (N=2,015) in the fall of 2011 (N=870), spring of 2012 (N=645), winter of 2013-2014 (N=202) and summer 2015 (N=323) via electrofishing. For each silver carp collected, presence (e.g., rough patch) or absence (e.g., smooth) of pronounced ridges on the top side of the pectoral fins was recorded, and an incision was made in the body cavity to identify gender. Based on the results of our evaluation, gender was correctly identified over 99% of the time (2,006 out of 2,015) based on the pectoral fin dimorphism. In the samples taken in the winter of 2013—2014 and summer of 2015, accuracy for silver carp shorter than 300 mm and longer than 800mm was 53.7% (19 out of 41) while accuracy for silver carp between 300 mm and 800mm total length was 98.9% (289 out of 292). This study provides a rapid assessment approach for evaluating silver carp gender.
A tag-release-recapture study was conducted to evaluate effects of size at release on survival, growth and yield of hatchery-reared mandarin fish Siniperca chautsi fingerlings stocked in a shallow Yangtze lake. In May and June 2012, a total of 2,400 juvenile mandarin fish were graded into three size groups, identified with coded wire tags and tail fin, and released into Xiaosai Lake. Mandarin fish were collected after the lake drained in December 2012. Overall, a total of 973 mandarin fish individuals were captured, with an average survival rate of 40.5%. Survival rate of large sized group (63%) is more than three times higher than that of small sized group (19.5%) and 1.5 times higher than that of middle sized group (39.1%). The mean final length and weight of mandarin fish increased with the increase of release size and showed significant difference among groups. Yield was significantly affected by release size, which was the highest in large sized group and the lowest in small sized group. The net income of stocked mandarin fish increased with the increase of fish size at release. Our results indicated that mandarin fish size at release can have a major impact on success of hatchery releases, and it is suggested that the optimum release size of mandarin fish should not be less than 50 mm in Xiaosai Lake.
We analysed spatial pattern in the fish assemblage structure along a longitudinal gradient of the Upper Yangtze River and the Three Gorges Reservoir. We tested the hypothesis that shifts from lotic to lentic environment affect the richness and structure of the fish assemblage. Samplings were carried out from 2005 to 2012 in four zones: 1) Hejiang reach, river upstream from the reservoir; 2) Mudong reach, upper part of the reservoir; 3) Wanzhou reach, middle part of the reservoir, and 4) Zigui reach, lower part of the reservoir. A total of 368706 fish representing 132 native species of 17 families were collected during the study period with Cyprinidae as the dominant group. The results showed that the native species richness decreased while the non-native species increased from river (Hejiang reach) to reservoir (Zigui reach). Patterns in fish assemblage ordination evaluated by correspondence analysis reflected a clear division of the riverine and reservoir zones. Uppermost sampling stations were characterized by species characteristic of flowing waters, whereas in the lowland most lentic species were captured. Further, 22 species, three functional groups (rheophilic, equilibrium, insectivorous) were identified for the upper reach and 16 species, three functional groups (herbivorous, planktivorous, stagnophilic) for the lowland reach by indicator species analysis (P<0.05). Therefore, it is evident that impoundment of the Three Gorges Reservoir is the major driving factor to structuring the fish assemblage structure along the longitudinal gradient from river to the reservoir. Different fisheries management actions should be made to conserve or rehabilitate native fish assemblages and control invasive non-native species.
The establishment of a highly efficient planktivore, Silver Carp (Hypophthalmichthys molitrix), in the Mississippi River Basin has been documented as having negative impacts on native planktivore populations. Silver Carp have the potential, to alter the trophic food web through negative interactions with native planktivores in large river systems. Due to increasing Silver Carp ranges, interactions between Silver Carp and other native planktivores is likely to increase. One abundant native planktivore that is often found in similar habitats as Silver Carp is Gizzard Shad (Dorosoma cepedianum). Potential competition for resources exists because of overlapping habitat use and forage. Given the similarities between these two planktivores, we sought to evaluate daily growth rates and determine hatch dates of age-0 Silver Carp and Gizzard Shad in the Middle Mississippi River. Silver Carp and Gizzard Shad were collected from the Middle Mississippi River using an electrified surface trawl from June through September with sizes ranging from 21—65 mm total length for Gizzard Shad and 24—85 mm total length for Silver Carp. A sample of age-0 fish (n=697) was collected at the end of the growing season including 292 Gizzard Shad and 405 Silver Carp. Size structure (total length in mm) of Silver Carp (49.05±0.41; X ̅ ± SE) was significantly greater (T=-16.43, df=695, P<0.001) than Gizzard Shad (38.95 ± 0.45). Hatch dates were similar between Silver Carp (July 26th to August 18th) and Gizzard Shad (July 28th to August 19th). Growth of Silver Carp (2.24 mm per day) was significantly greater (P<0.001, T=-11.1, df=82) than Gizzard Shad (1.72 mm per day). Mortality was similar between Silver Carp (28.1%) and Gizzard Shad (25.1%) at this early life stage. The faster growth rates in Silver Carp result in Silver Carp entering the winter season larger in size with likely an increased capacity to consume plankton and decreased predation ultimately leading to higher recruitment. Knowing that there exists an overlap between Silver Carp and Gizzard Shad diets and habitat could alone call cause for concern. Adding that spawning occurs at a similar time and Silver Carp have the ability to outgrow Gizzard Shad early in life leads to major concerns about food web balance. Knowing that invasive planktivores have already shown to alter food webs in aquatic systems in North America, extra caution should be taken.
A comprehensive investigation on macrophyte community in Hongze Lake was conducted seasonally from May 2010 to February 2011. Overall, twelve species representing eight families of macrophytes were identified in Hongze Lake, including nine species of submerged plants, two species of floating-leaved plants, and one species of emerging plant. In general, Potamogeton malaianus, P. maackianu, P. pectinatus and P. crispus were the four dominant species throughout the whole year, the highest biomass of macrophytes was presented in autumn, followed by summer and winter, while spring had the lowest biomass of macrophytes. Based on field data, we used kriging interpolation in ArcGis to map the spatiotemporal distribution of the entire macrophyte community as well as each of the four dominant species. From the GIS maps we observed that the northern area of the lake, namely the Chengzihu region, had the highest biomass of macrophytes potentially as a result of better water quality and greater transparency. Potential factors that affected the community structure, biomass, and distribution patterns of macrophytes considerably were then discussed. The results of this study illuminate the need for more information on the role and importance of aquatic macrophytes in shallow lake ecosystems. Conservation of macrophytes should be taken to maintain the lake ecosystem health.
Schizothorax macropogon and Ptychobarbus dipogon are important economic fishes in the Yarlung Zangbo River. Both are Schizothoracinaes containing a variety of essential fatty acids with high nutritional values. As food products, the textural characteristics of their meat determine important factors like taste or methods of treatment. To explore the preservation and utilization of fish resources in the Tibet Autonomous Region, China, the texture profile analysis (TPA) method was used to analyze 12 textural parameters. Fish were captured from the Yarlung Zangbo River in Shigatse and Nyingchi City. Principal component analysis showed that the texture of P. dipogon captured from the Nyingchi segment was different from the same species captured in the Shigatse segment, and different from S. macropogon captured from both segments. Factorial analysis indicated that the textural characteristics of Schizothoracinae fishes in Tibet Autonomous Region can be summarized as hardness indices, overcome attraction indices and contractility indices, of which the accumulated variance contribution rate of the first four principal component factors was 81.472%. The three categories of the four principal component axes could be the main deciding parameters of the textural characteristics of Schizothoracinae fishes in Tibet Autonomous Region. This provides scientific data for subsequent development and utilization of Schizothoracinae fishes from the Yarlung Zangbo River in different geographical areas.
To investigate the influence of artificial substrates (AS) on the growth performance of fish in pond poly-culture systems, a feeding experiment was conducted in six individual earthen ponds, which were divided into two groups. The ponds with AS in the water were labeled as the " AS group” and that without the use of AS were labeled as the " control group” (three ponds per group). A total of 3867 common carp [Cyprinus carpio, (310±11) g], being artificial-feeds feeding fish, and 370 bighead carp (Aristichthys nobilis) and silver carp [Hypophthalmichthys molitrix, (810±15) g], being plankton filter feeding fish, were divided into six groups and cultured in the ponds respectively. The common carp in each pond were fed with commercial particle feeds three times a day and the feeding period was 62 days. Water quality, concentration of plankton and the bacterial community presenting in the water and sediment were monitored during the experiment. At the end of the experiment, all fish were harvested and the growth of the fish and feed efficiency ratio were determined. Results showed that the weight gain rate and feed efficiency ratio of common carp in AS group was significantly higher than that of the control group. Final body weights of bighead carp and silver carp in the AS group were significantly lower than that of the controls. Water transparency and diversity indices of the bacterial community in the AS group were significantly higher than that of the control (P<0.05) and the concentration of plankton in the AS group was lower than that of the control. Results showed that the application of AS in poly-culture ponds was beneficial for the growth of common carp, being artificial-feeds feeding fish, while it was not beneficial for the growth of bighead carp and silver carp, being plankton filter feeding fish.
Many efforts have been devoted to developing, constructing and refining fishways or fish passage facilities to facilitate the target fish species to pass barriers in fluvial systems. Once dominated by an engineering-focused approach, fishways science nowadays involves a wide range of disciplines from fish behaviour to socioeconomics, and to complex modeling of passage prioritization options in river networks. Designing efficient fishways, with minimal passage delay and post-passage impacts, requires adaptive management and continued innovations. After the completion of fishways construction, corresponding management systems usually need to be improved as well. In the current study, we first reviewed international fishways adaptive management systems (e.g., aspects of development, construction, and management) from 1991 to 2017 reporting on " fishway”, " fish passage”, " fish” and " dam”. The functions of fishways gradually transferred from conservation of economic stocks to overall biodiversity conservation, from facilitating upwards to both upwards and downwards passages, from developing a single project to considering the entire river basin, from fish passing function to habitats restorations as well, and from pure engineering construction to considering adaptive management. Finally, we discussed adaptive management systems and management prospects of fishways for China.
This study examined anesthetic behaviors of Schizothorax o’connori Llord in two size ranges as induced by MS-222, to acquire useful information on anesthesia of said highland fish species in out-of-water activities (surgery, labeling, measurement, etc.). Test results indicated that for both large (25.0±1.5) cm and small-sized (14.8±2.3) cm specimens, respiration rates showed no significant change in anesthetic stages I to III, and only begun to significantly decline after entering stage IV. The effective concentrations of MS-222 were 150—180 mg/L and 150 mg/L for two sizes, respectively. The 150—180 mg/L caused large specimens to enter anesthetic stage IV within 5min, and recovered within 5min; the 150 mg/L caused small specimens to enter stage IV within 5min, and recovered within 7min; both doses ensured a 100% survival rate after immersion for 20min. For large specimens anesthetized at 180 mg/L for 5min and exposed to air for 0—15min, there was no significant difference in recovery times (P>0.05); for small specimens anesthetized at 150 mg/L for 5min and exposed to air for 0—15min, there were significant differences in recovery (P<0.05).
The lower Mississippi River (LMR) has been heavily modified for multiple human purposes such as navigation, flood control, and bank stabilization. However, the LMR simultaneously supports a diverse fish fauna that includes recreational and commercial fisheries. Due to river training and diversion structures constructed during the past 80 years, the historic characteristics of the LMR have been drastically altered and have likely influenced fishes and fisheries in the system. One common restoration measure used throughout the LMR has been to " notch” wing-dike structures that close secondary (side) river channels. Dike notching allows year-round flows through secondary channels, which enhances habitat diversity and promotes biological productivity at the ecosystem scale. Although notching is presumed good for LMR fishes and other biota, few studies have examined its effects on fish assemblages. In this study, fish assemblages were sampled at seven LMR secondary channels spanning from river kilometer (rkm) 628 (Louisiana-Mississippi, U.S.A.) upstream to rkm 1504 (Missouri-Kentucky, U.S.A.). Four secondary channels were termed " permanent” (i.e., with notched dikes) while three secondary channels were termed " temporary” (i.e., without notched dikes). Fishes were sampled by boat-mounted electrofishing conducted during falling and low stages from 1995—1997. Fish assemblages differed between permanent and temporary secondary channels, and varied somewhat between falling and low stages. Gizzard shad (Dorosoma cepedianum), threadfin shad (D. petenense), and white bass (Morone chrysops) demonstrated consistent preferences for low-current conditions associated with temporary secondary channels. Conversely, blue catfish (Ictalurus furcatus), flathead catfish (Pylodictis olivaris), and freshwater drum (Aplodinotus grunniens) were more associated with permanent secondary channels. Future restoration strategies in the LMR should consider dike notching and resultant maintenance of permanent secondary channels in selected river reaches. However, temporary secondary channels also contain unique fish species, and also appear to be important sites of riverine primary production. Restoration strategies should consider a balance of both secondary channel types, which should support the greatest biodiversity for the LMR ecosystem.
This study is based on monthly sampling (from April 2013 to April 2015) of 18 fish species representing three families. Samples were obtained using benthic fyke-nets, block nets, and multi-mesh gillnets in Lake Kuilei, a shallow lake of the Yangtze River basin, China (N 31º24', E 120º51'). Using ordinary least-squares linear regression, length-weight relationships of these fish species were estimated, with equations for 3 species reported for the first time. The maximum total length records of the 15 species exceeded those reported in FishBase. This paper provides new LWR equations for these species to be included in FishBase.