Abstract:Measuring fish target strength (TS) is the foundation of fisheries acoustic research and its applications. TS measurements focused on fish in the Yangtze River are lacking or do not meet the needs for a fisheries resource assessment. Variations in TS of four freshwater cultured fish species with different swim bladder structures were measured with a BioSonics DT-X (199 kHz) split beam echosounder in the horizontal direction. The four fish were Vachell's bagrid fish (), crucian carp (ex situ experiment was carried out in a small T-shaped tank during June and October 2015. The tank was constructed of eight fiberglass-reinforced plastic boards. Polyurethane foaming plastic cotton was pasted on the internal face of the tank to absorb any sounds reverberating from multiple echoes. Twenty-nine individuals were anaesthetized and tethered on a horizontal rotation support, in turn, and TS was measured at different horizontal angles. The angles were changed from -90° to 90° at an interval of 5°. Individual TS was measured for 300 pings at each angle. The results showed that mean TS of fish was affected by the aspect angle. Maximum TS occurred in the lateral direction, and minimum TS occurred in the head-tail direction. The difference between the maximum and minimum TS was about 10 dB. A cos functional relationship was observed between the measured TS and the sound wave incident angle, as well as from the fish dorsal-ventral direction. Fish TS values were smaller in the dorsal aspect than those in the side aspect. These differences may have been affected by the shape of the swim bladder and its position in the body. Two X-ray images were taken from the side and dorsal aspects of each fish to understand the inner structure of the fish and the swim bladder. TS of fish with a one-chambered swim bladder was smaller than that fish with a multi-chambered swim bladder, even though standard length (SL) of the one-chambered fish was longer. Relationships between TS-length (TS-total length, TS-standard length), and TS-weight (TS-fish weight) were derived in three orientations:lateral (from -90° to -80° and from 80° to 90°), oblique (from -75° to -20° and from 20° to 75°), and in all of directions. Linear regression equations were prepared for the side and dorsal aspects of the four fish species. The side aspect linear regression equations for mean TS with fish SL in the lateral position were:TS__vbf=19.5lg(SL)-63.4(=0.66), TS__cc=19.7lg(SL)-56.6(2=0.89), respectively, where SL is fish standard length, vbf is a fish with a one-chambered swim bladder (Vachell's bagrid fish), mf is mandarin fish, cc is crucian carp, and gc is grass carp.). The dorsal aspect linear regression equations for mean TS with fish SL in the lateral position were:TS__vbf=28.7lg(SL)-75.7(=0.88), TS__cc=19.1lg(SL)-59.9(2=0.99), respectively. In this experiment, the fish's body was tethered tightly on a rotational support, so fish behavior was limited. The beam was narrow in the short distance. Although the beam covered the entire body, mean TS was affected by the swim bladder position in the body. Hence, some differences between the measurements were observed. In the future, the mean TS of these fish species should be measured or in a net cage, so researchers can compare the results with this study to improve the accuracy of converting length and assessing resources from the TS measure-ments. This study will help guide fish behavior research and fisheries resource assessments in the Yangtze River.

Abstract:Establishing meiotic gynogenesis, mitotic gynogenesis, and inbred lines is important for trait purification during selective fish breeding. Yet how these three genetic pathways affect heredity remains the focus of much genetics research. In this study, we used the female parents from family F09119 to establish mitotic gynogenesis (F1346), meiotic gynogenesis (F1324), and an inbred line (F1313) and analyzed their growth and genetic characteristics. Body length, body width, and weight were measured in the three families from 85 to 388 d post fertilization (dpf). Results on 338 dpf showed that growth rate of F1346 was the highest[body length, (28.89±2.77) cm; body width, (10.00±1.21) cm; and weight, (254.91±83.11) g] and that of F1324 was the lowest (<0.05). Survival rate of F1324 on 263 dpf was the highest (46.50%) and that of F1346 was the lowest (26.80%). The numbers of alleles for mitotic gynogenesis, meiotic gynogenesis, and the inbred line were 2.0, 2.0 and 2.35, respectively. The effective numbers of alleles were 1.87, 1.95, and 2.1; polymorphic information content values were 0.35, 0.36, and 0.4; and mean observed heterozygosity values were 0, 0.8155, and 0.6366, respectively, indicating that genetic variation of mitotic gynogenesis and meiotic gynogenesis was less than that of the inbred line. The trend for unbiased expected homozygosity was F1313 (0.503) < F1324 (0.5105) < F1346 (0.532) and that of unbiased expected heterozygosity was F1313 (0.4967) > F1324 (0.4894) > F1346 (0.4679). Homozygosity of meiotic gynogenesis was 1.0421-fold higher than that of meiotic gynogenesis and 1.0577-fold higher than that of the inbred line, whereas that of meiotic gynogenesis was 1.0149-fold higher than that of the inbred line. The genetic distance between F1346 and F1313 was longest (0.1568) but genetic similarity was the lowest (0.8549), whereas the genetic distance between F1346 and F1324 was the shortest (0.0406), and genetic similarity was the greatest (0.9602). These results provide a theoretical basis for establishing an inbred line of and analyses of genetic variations among meiotic gynogenesis, mitotic gynogenesis, and the inbred line.

Abstract:The bacterium Cynoglossus semilaevis aquaculture industry. The fundamental approach has been to cultivate a new disease-resistant strain by combining traditional breeding methods with molecular techniques. In this study, bulked segregant analysis and quantitative trait loci (QTL) mapping were used to screen for disease-resistance markers. A total of 100 individuals were selected to form the F1412 family (nomenclature rule:F+year+family number:survival rate, 52.22%), which was challenged with , and 169 microsatellite loci were detected across all chromosomes. Following the genomic scan, the scaffold479_23523 marker in the DNA pool was significantly different between the resistant and susceptible groups (=0.000006). Ninety-four individuals were genotyped using all 32 simple sequence repeat markers on LG18, where scaffold479_23523 was located. Three new linkage groups (LG18, LG18F, and LG18M) were identified. Furthermore, two different analytical models were applied to perform a single marker analysis and composite interval mapping with different levels of significance in LG18, LG18F, and LG18M, respectively. In model 1, three significant markers (scaffold4475_71287, scx9-1, and cyse80) and one very significant marker (scaffold080437) were identified, and the qE-F1 resistance-related QTL was detected. The scaffold479_23523 marker was the left LG18F marker with a p-value of 0.0516 in model 1. Model 2 detected four significant markers (hncyse110, scaffold414_19940, scaffold4475_71287, and cyse80), one very significant marker (scaffold08043), and the qE-M1 and qE-M2 QTLs. Both scaffold080437 markers were significantly different (<0.001) in the two models. Four markers (scaffold080437, scaffold479_23523, scaffold4475_71287, and cyse80) may be closely associated with resistance to . qE-F1 explained 87.36% of the phenotypic variance and contained G18M qE-M1 and qE-M2. Thus, qE-F1 was considered a major candidate region for genome, three immunity-related genes, such as meteorin-like, the WD repeat domain phosphoinositide interacting 2, and Toni beta-propeller repeat containing 1, were detected inside qE-F1. This is the first study to identify resistance-related markers and conduct a related QTL analysis in . These results provide a foundation for selective breeding of disease-resistant .

Abstract:In the present study, growth rates of Parabramis pekinensis (PP), and their hybrids (AT, TA, AP, and PA) were compared to investigate growth and morphological differences. Three multivariate morphometric analyses were conducted to assess morphological variations based on meristic parameters, measurable scaling parameters, and truss network scaling parameters. In the first group, absolute weight gain rates of AT and TA were significantly greater than that of TT but were all lower than that of AA (0.36 g/d) (<0.05). Growth rate of AA was 2.4, 1.2, and 1.3 times that of TT (0.15 g/d), AT (0.30 g/d), and TA (0.27 g/d), respectively. In the second group, the absolute weight gain rate of AA was also the largest (0.24 g/d), which was 1.7, 1.4, and 1.6 times greater than that of PP (0.14 g/d), AP (0.17 g/d), and PA (0.15 g/d), respectively. The growth rate of AA was significantly faster than that of TT and PP (<0.05), and the growth rate of their hybrid offspring was between that of their parents; lower than that of AA, but higher than that of TT or PP. In addition, no differences in countable characters were detected among the seven groups (>0.05). Based on the nine measurable scaling parameters and 20 truss network scaling parameters, a cluster analysis revealed that the hybrids were closer to their female parent than to their male parent; namely, the relationships with TA and TT were closer than the relationships with AA, AT, AP, and PA. A discriminant analysis using the morphological characteristics of the seven breeding groups was carried out, resulting in a high comprehensive discriminant rate of 86.30%. A principal component analysis (PCA) showed that three main PCs were obtained with a cumulative contribution rate of 95.81% of total variation, which represented the major morphological variation in the seven breeding groups. Furthermore, traits with a larger feature vector absolute value for PC1 were mostly concentrated in the head and dorsal-ventral axis, whereas traits influenced by PC2 were mostly concentrated in the tail. Overall, these results provide a theoretical basis for fish breeding and identifying germplasm.

Abstract:Seasonal variations in gonadal development of third-generation golden shell colored strain were investigated in relation to environmental factors from November 2013 to October 2014, and the general nutrient components of the mantle, gill, gonadal-visceral mass, and adductor muscle were examined. In addition, the nutritive content of the golden shell colored strain was compared with that of commercially cultured oysters. The histological analysis showed that the female to male sex ratio was approximately 1:1, and the gonads of both sexes developed synchronously. Gametogenesis began in February and spawning started in June and appeared to continue until August when water temperature was high and food was abundant. Mean oocyte diameters increased gradually from the beginning of gametogenesis and reached their maximum (36.99 μm) before spawning. The biochemical analyses showed that total gonadal fat content was relatively low compared with that of total protein and glycogen, but fat accumulated as the gonads developed, indicating that lipid is a major component of bivalve oocytes. Glycogen content decreased significantly during sexual maturation, whereas total protein content increased as the gametes matured. Golden shell colored oysters had significantly higher protein content, but significantly lower glycogen and fat contents in the mantle than those of commonly cultured oysters (<0.05). General nutritional composition was not different among the other three organs. These results indicate that nutritive content was similar in the common and golden shell colored oysters and provide data for breeding the golden shell colored strain in the future.

Abstract:The razor clam is wildly distributed in China, Japan, and Korea. The razor clam has high nutritive and economic value and is one of four marine bivalves produced in China. Artificial breeding and frequent inbreeding have decreased the genetic diversity of razor clams, and the germplasm resources are degraded. As a result, massive razor clam mortalities occur occasionally. Cultured clams are generally small and have poor disease resistance, and no superior commercial razor clam varieties have been bred for the commercial market. Therefore, improving genetic traits and breeding outstanding varieties of razor clams via artificial selection are primary goals of razor clam culture. In this study, six natural populations of (Zhejiang Xiangshang and Leqing populations, Fujian Xiapu and Changle populations, Jiangsu Sheyang and Shanghai Chongming populations) were selected as the F₀ material structure foundation populations, and continuous multiple-generational breeding (selection intensity:2.063) was carried out using the mass selection method. The growth difference between the F₅ breeding strain and a control population was compared. The selection response, realized heritability, and F₅ heredity acquisition were evaluated. The results showed no differences in egg diameter or fertilization rate between the F₅ generation (>0.05) and the control group. However, the metamorphosis rate, survival rate, and late growth in shell length of the F₅ generation were significantly superior to those of the control group (<0.05). Variations in the selection response of shell length, realized heritability, and heredity acquisition of F₅ during days 7-360 were 0.30-0.78, 0.14-0.37, and 4.83%-42.18%, respectively, and the means were (0.49±0.06), (0.23±0.08), and (26.49±11.73)%, respectively. These results suggest that continuous multiple-generational breeding of razor clams was effective, as it significantly improved survivability and the major economically important traits. Continuous selection of five generations of razor clams was effective, making further breeding to identify new razor clam varieties with desirable traits possible. The genetic gain in shell length was generally low, probably because of genetics and environmental factors. Razor clams are a mudflat bivalve that hide in silt, and their long body reduces adaptability to the environment. Hence, breeding should focus on weight selection to obtain more practical results.

Abstract:is mainly distributed in coastal waters off southern China and is a warmwater, economically important shellfish. is characterized by rapid growth, a short breeding cycle, suitability for high density cultivation, and is nutritious, so there is high demand among consumers. Guangdong is often affected by typhoons, so more rain falls there than in other provinces. Sea salinity drops when rainfall increases, and the osmotic pressure in aquatic animals varies because of salinity changes, which can result in massive mortalities of abalone. is a local species in Guangdong, making it particularly susceptible. Response surface methodology (RSM) is a collection of statistical and mathematical techniques to optimize a process. This methodology generates an empirical mathematical model that defines the effect of an inde-pendent variable on a response of interest to optimize the response. RSM has been applied in ecotoxicological studies of marine bivalve larvae and to investigate the effects of environmental variables on embryonic and larval develop-ment. RSM has not been used in any gastropod nutritional studies. In this study, the synergistic effects of salinity and stress duration on alpha-amylase gene expression were assessed using central composite design and RSM. The results show that the linear effects of salinity on alpha-amylase gene expression were not significant (P<0.05), suggesting that expression of the amylase gene was affected by stress duration. In addition, the quadratic effects of salinity on amylase gene expression were significant (<0.05), but the quadratic effects of stress duration on amylase gene expression were not significant (>0.05). No synergism was detected between salinity and stress duration. The RSM model equation for the relationship between amylase gene expression and the two factors was established ( value was 65.80%, and the Pre. values was 50.18%, suggesting a good model fit for prediction. Maximal amylase gene expression was observed when salinity was 31, and stress duration was 36 h. is affected by many factors, as it is cultured in a marine environment. Additional factors should be studied in the future.

Abstract:is a popular food in China, Japan, and Korea because of its fresh meat and high nutritional value. In recent years, desalination marine fish farming has aroused interest, and is a marine model organism for studying low-salinity aquaculture because of its ability to tolerate a wide range of environmental salinities. This fish species has been used to explore the molecular mechanisms of osmoregulation in marine teleosts due to its small genome, and>95% of the genome has been sequenced. Studies have shown that can survive in hypo-osmotic conditions such as 10%-25% saltwater, but the fish does not survive in freshwater. Therefore, to investigate the molecular mechanism of low-salinity tolerance in IgM), Na-K-Cl cotransporter 1 () was analyzed using real-time quantitative polymerase chain reaction (qRT-PCR) analysis of the gill and kidney from juvenile juveniles were divided randomly into five groups and maintained in water with salinities of 32 (control) 16, 12, 8, and 4 for 72 h. The results show that all three genes were expressed in gill and kidney. expression levels were not different between the two tissues ( expression level in the gill was significantly higher than that in the kidney ( expression decreased initially and then increased in the gill, whereas it decreased initially, increased, and finally tended to stabilize in the kidney in fish under acute low-salinity stress. More notable differences were detected in the gill between the low-salinity and control groups compared with those in the kidney at the same time points. expression decreased in the gill but increased in the kidney under low-salinity stress, and expression levels in the gill were higher at all time points than that at 0 h. expression levels in the gill of fish in the low-salinity groups were significantly lower than those in the control group at 6 and 72 h ( expression levels were observed in the low-salinity groups at 3 h, 6 h, 24 h, and 72 h compared with those in the control. Changes in kidney IgM, NKCC1, and T. rubripes were maintained in different salinities and for various durations. These results suggest that these three genes play an important role in the low-salinity tolerance of and provide basic data for clarifying the molecular mechanisms of osmoregulation in .

Abstract:is a fish that migrates to spawn, displays rapid growth and high economic value, and is a good substitute food for Clupea pallasii, Opisthonema oglinum, Engraulis japonicus, Sardinops melanostictus, and . In this study, development of the vertebral column and pectoral and caudal fins of larvae (1-51 days post hatching[dph]) is described using a cartilage and bone clearing and staining technique. The results show that the vertebral column started to develop from hemal arches, neural arches, and hypurals at 10 dph. The neural and hemal arches extended to the neural and hemal spines at 16 dph, respectively. Segmental bone rings formed at 19 dph, and the vertebral column was completely ossified by 23 dph. The appendicular skeleton developed in sequence from the pectoral, caudal, dorsal, and anal to ventral fins. Development of the pectoral fins started when the coracoid appeared at 2 dph. Cartilage of the appendicular pectoral fins formed at 13 dph, and the pectoral girdle and cleithrum ossified by 19 dph. The caudal fin began to develop when the hypurals appeared at 5 dph, and two sections of the epural, one section of the urostyle, and six sections of the hypurals formed at 12 dph. The caudal vertebra and caudal fin began to ossify 19 dph and were completed by 23 dph. The dorsal and anal fins ultimately developed 18 and 22 fins, respectively. The order of development of the appendicular skeleton was the same as that of other fish. The appendicular skeleton, hemal arches, hemal spines, neural arches, neural spines, dorsal ribs, and ventral ribs had cartilage ossification stages. The vertebra and supracleithrum were formed directly from the periosteum, as cartilage staining had no effect on vertebra or the cletthrum. Developmental deformities were detected in trunk vertebra, but the rate was lower than that observed in . Some caudal vertebrae grew abnormally during the trial. Early exercise had an effect on deformity of longer caudal vertebrae. However, caudal vertebrae lacked protection from forks in the neural arch and ventral ribs. Abnormal growth may have occurred due to nutrition, water quality, or other factors. Studying the early development of the vertebral column and pectoral and caudal fins of is important to understand functional adaptation during early development, environmental optimization, and to classify and identify fish.

Abstract:The benthic marine bivalve, , is a commercially caught species and is exploited in many southern coastal cities of China, where it is sold by wet weight. However, efficient and effective management strategies are needed for a sustainable supply of this wild resource, and an understanding of reproductive biology and the fishery is required. The aim of this study was:(1) characterize gonadal morphology and histology; (2) describe the main gametogenic events and link them to maturation stage, and (3) characterize spawning, eggs, and newly hatched veliger larvae. Samples were collected monthly from January 2012 to January 2013 from Cangnan Bay, south of Zhejiang Province, China. Routine histological techniques were used to characterize the gonadal development stages. The results show that the clam is characterized by typical gonadal development of bivalves, and the reproductive cycle was divided into proliferation, growing, maturation, breeding, and suspensive stages. Gonadal maturation of clams from the South Zhejiang coast was completed over 1 year. The spawning season occurred from early June to mid-September, and peak spawning occurred from early July to mid-August, when water temperature was 24.8-29.4℃. This clam is dioecious, and gametes of both sexes are released at about the same time. The female to male ratio was 1:1. Spawning was induced by shade-drying or running seawater. Embryos developed in salinity of 28 and temperature of 29℃. The D-shaped larvae hatched after 16-20 hours at 29℃. The larvae developed into post-larvae and completed metamorphosis into spat after 5-6 days, with a mean shell length of 200 μm.

Abstract:Aquatic plants are one of the most important ecological factors in Chinese mitten crab culture. However, the effects of aquatic plants on growth of Chinese mitten crab, have not been quantitatively evaluated, and their effects on nutritional quality remain vague. In this study, we investigated the influence of an aquatic plant () on growth and nutritional quality of Chinese mitten crab, and compared growth and amino acid and fatty acid composition of adult Chinese mitten crab reared in concrete ponds with and without <0.05) in body weight, carapace length, carapace width, and condition factor between Chinese mitten crabs reared with and without >0.05) in the hepatopancreas or gonado somatic indices were observed between crabs in the two rearing environments. Amino acid, essential amino acid, and flavored amino acid contents in the muscle of Chinese mitten crabs reared in ponds with were significantly higher than those in crabs reared in ponds without <0.05). The flavored amino acid contents in the hepatopancreas of female crabs reared with were significantly higher than those in crabs reared without <0.05), but no differences were detected in males (>0.05). Muscle fatty acid composition and content were not different in crabs reared in the ponds with and without plants. However, saturated fatty acid, monounsaturated fatty acid, and polyunsaturated fatty acid contents in the hepatopancreas were significantly higher in crabs reared in the ( enhances growth of Chinese mitten crab and should help improve the nutritional quality of Chinese mitten crab.

Abstract:Five male greenhouse reared Chinese soft-shelled turtles ( from the eco-pond for Chinese mitten crabs () (defined as ER) were dissected to collect muscle, soft apron and liver. The proximate composition and amino acid and fatty acid contents in edible tissues were determined to investigate differences in biological indices and nutrient composition of edible tissues. The results showed that the soft apron index and hepatosomatic index of GR were significantly higher than those of ER (<0.05). Muscle crude ash and soft apron moisture contents were significant higher in ER than those in GR (<0.01), while the higher soft apron protein content was detected for GR, but no differences in any other proximate composition factors were detected between in the two environments. The contents of most amino acids, total essential amino acids (∑EAA), and total amino acids (TAA) in muscle and the soft apron of GR were significantly higher than those of ER (<0.05), but higher cysteine content and ∑EAA/TAA ratio were found for ER. The muscle and soft apron essential amino acid scores (EAAS) were similar in ER and GR, but higher mean EAAS was observed in ER than that in GR. C_18:1n9 and C_18:1n7 fatty acid and total monounsaturated fatty acid contents in muscle were significantly higher in GR than those in ER, but C_22:6n3, total polyunsaturated fatty acid (∑PUFA), ∑n-3PUFA, total highly unsaturated fatty acid, and the n-3/n-6 ratio were significant higher in ER than those in GR ( contents were significantly higher in GR than those in ER (<0.05), but no differences were detected in any of the other fatty acids. These results indicate the high nutritional value of male reared in the two environments.

Abstract:The long-term changes in fish ecological structure and fishery resources were studied in the Eastern Seas of China (Bohai Sea, Yellow Sea, and East China Sea) and the South China Sea based on 1983-2013 catch statistical data, using fish trophic level (TL), the FiB index, and the main fish cluster caught by Chinese fishing vessels. A correlation analysis of the change in fish ecological structure based on fishing method was also conducted. The results show that mean TL has declined among the 25 main fish species caught in the Eastern Seas of China. The contribution of carnivorous fish in the lowest class to total catch has increased 60%, the contribution of carnivorous fish in the middle class to total catch has increased 129%, and the contribution of carnivorous fish in the advanced class to total catch has decreased 51%. No changes in mean TL have occurred in the South China Sea; however, the contribution of carnivorous fish in the lowest class to total catch has decreased 6%, the contribution of carnivorous fish in the middle class to total catch has decreased 43%, and the contribution of carnivorous fish in the advanced and middle classes to total catch has increased 198%. These results suggest that fisheries resources in the Eastern Seas of China, but not those in the South China Sea, are declining.

Abstract:Two acoustical surveys were conducted using a Simrad EK60 scientific echosounder (38 kHz split-beam transducer) in the Nansha, Zhongsha, and Xisha areas during spring 2013 and 2014 to explore the abundance and spatiotemporal distribution of mesopelagic fish species in the central-southern part of the South China Sea. The abundance and distribution were estimated using the echo-integration method based on acoustic data and mid-water trawl samples. We identified 79 fish and squid species in 60 genera, 37 families, 16 orders, and 3 classes in the Zhongsha and Xisha areas during spring 2014. Osteichthyes was the most abundant (65 species), followed by Coleoidea (13 species), and Chondrichthyes was only represented by one species. Stomiidae, Myctophidae, and Gonostomidae (Osteichthyes) were the most abundant families and were represented by 20, 13, and 6 species, respectively. The nautical area scattering coefficient (NASC, m²/nmi²) of mesopelagic fish in the Nansha area was much lower than that in the Zhongsha and Xisha areas, and the former presented more obvious ascending intensity at night. The NASC composition of fish living in 10-200 m depth range at night was not different from that of fish living in 200-1000 m during the day in the Nansha area in spring of 2013, but the difference was significant in the Zhongsha and Xisha areas in spring of 2014. The NASC composition values of fish living in 200-1000 m during the day for the different latitude scopes in the Nansha, Zhongsha, and Xisha areas were significantly different. The NASC of mesopelagic fish in the central-southern part of the South China Sea was (2387±601) m²/nmi². We estimated the abundance of mesopelagic fish in the central-southern part of the South China Sea to be (82±21) million tons based on the existing mesopelagic fish target strength parameters and the median value. These results indicate that the NASC of mesopelagic fish in the central-southern part of the South China Sea was 29.2% higher than the global average. Mesopelagic fish are a potential major strategic fishery resource and are very important for China to develop.

Abstract:Chinese sturgeon, , is an ancient and large anadromous fish in the family Acipenseridae (Acipenseriformes, Actinopterygii) and has been classified as Critically Endangered on the IUCN. Hydroelectric dam construction, including the Gezhouba Dam and the Three Gorges Dam on the upper Yangtze River has resulted in a sharp decline in the wild populations of , indicating that cultured stocks may serve as the only source for species conservation. Many rehabilitation efforts, as well as controlled reproduction, have been undertaken to prevent this endangered species from becoming extinct. However, Chinese sturgeons in captivity are exposed to a range of stressors, including variable temperatures and water quality and potential pathogens. Non-tuberculous mycobacteria (NTM) causes cutaneous lesions and spreads to internal organs via the circulatory or lymphatic systems. In this study, a cultured F₂ generation of Chinese sturgeon was infected with NTM, and developed typical symptoms of ascites, peritoneal granulomas, kidney edema, and a grey white liver. An acid-fast Mycobacterium liflandii identified by 16S rDNA and IS2404 sequence analyses. Nine blood indices were significantly different between ten healthy and four NTM-infected F₂ Chinese sturgeon (<0.05). Total white blood cell count, neutrophils, and alanine aminotransferase levels were significantly elevated but the other indices decreased significantly, including lymphocytes, sodium, chlorine, calcium, total protein, and globulin, suggesting that the liver and kidney were badly damaged by NTM. An infected F₂ Chinese sturgeon with serious ascites was treated for 75 days with a combination of rifampicin, erythromycin, and amikacin. The ascites decreased significantly early in the treatment, and five blood indices increased significantly (<0.05), including red blood cell count, hemoglobin, packed cell volume, mean corpuscular volume, and globulin, indicating that the antibiotics were effective. However, fish con-dition deteriorated over time and they were eventually euthanized. These results show that mycobacteriosis is a widespread and extremely harmful zoonosis of Chinese sturgeon. It is essential to promote research on a vaccine, drug susceptibility of isolated strains, medication dosing, and side effects in Chinese sturgeon to reduce endangering the health of the population. Furthermore, early supervision and diagnosis of this disease is required. We detected mycobacteria in the skin mucus of all infected Chinese sturgeon and in apparently normal individuals, indicating that sampling skin mucus is a good indicator of the distribution of the pathogen. Additionally, the isolated strain was found in water where infected Chinese sturgeon were held; therefore, it is important to monitor mycobacteria in water and in the fish population. How and where the Chinese sturgeon became infected with mycobacteria remain unknown. Fur-ther monitoring studies are necessary to evaluate the pathogenic potential of this strain in China for susceptible and receptive fish hosts and for mammals. This information will be useful to predict future epidemics and to implement ad-equate preventive and control measures.

Abstract:Chinese giant salamander ranavirus (CGSRV) is a new pathogen that has been identified recently in cultured Chinese giant salamanders () and is causing serious damage associated with high morbidity and mortality. In this study, Chinese giant salamanders were infected with an intraperitoneal injection of CGSRV at a concentration of 1.0×10^6.5 TCID₅₀/mL. Liver, spleen, kidney, lung, intestine, stomach, skin, muscle, heart, and brain were collected 0 d, 3 d, 5 d, 7 d, 9 d, 13 d, and 16 d after infection for pathological and tissue tropism examinations. Paraffin sections and hematoxylin and eosin staining were used for the histopathological observations, SYBR Green quantitative polymerase chain reaction (qPCR) was performed to examine the dynamic quantitative distribution and tissue tropism of CGSRV. The histopathological examination revealed extreme lesions caused by CGSRV in many tissues and organs, particularly in the liver, spleen, kidney, muscle, and skin, and basophilic or eosinophilic inclusions appeared in damaged cells. Hepatocytes and renal tubular epithelial cells had degenerated 3 d after infection, and eosinophils and lymphocytes had infiltrated the renal interstitial and central veins of hepatic lobules. Degeneration, necrosis, and inflammation progressed in parenchymatous organs, and catarrhal inflammation was observed in the gastrointestinal tract after 5-7 d. Necrosis, exfoliation of the epidermis, and degeneration and necrosis of muscle fibers were detected after 9 d. Degeneration, necrosis, and inflammation were extensive in the liver, the number of lymphocytes decreased remarkably, glomerulonephritis with exudation and necrosis was detected in the kidney; hemorrhaging, necrosis and infiltration of inflammatory cells was detected in the skin and muscle, and myocarditis was observed in the heart after 13-16 d. The SYBR Green qPCR results indicated that the number of CGSRV tissue copies increased to 2.36×10³-1.84×10⁹ copies/mg tissue during infection. The number of copies was higher in lung, intestine, liver, spleen, kidney, skin and muscle, indicating that CGSRV has a broad tissue distribution and that the liver, spleen, kidney, skin, and muscle were target organs for viral replication and damage. A positive correlation was observed between the quantity of virus and pathology.

Abstract:Ictalurus punctatus is native to the Americas and a superior freshwater fish cultured worldwide. However, acute mortalities often occur during aquaculture. In addition, the disadvantages of antibiotics have been highlighted, and a safe and effective substitute has become a hot topic. Thus, many studies have been published on the beneficial effect of probiotics, and most have targeted the microflora of the gastrointestinal tract, but few studies have investigated microflora of the gills and skin. To provide a theoretical basis to study gill, skin, stomach, foregut, and hindgut microorganisms and to screen probiotics from , we compared the microbial structures of the gills, skin, stomach, foregut, and hindgut from of different weights and explored the correlation with aquatic flora using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and quantitative-polymerase chain reaction (Q-PCR). All samples possessed rich bands, but the location, number, and color of the bands were quite different among samples. The mean numbers of DGGE bands detected in the organs from low to high were gills, skin, foregut, hindgut, and stomach. The Shannon diversity index and evenness and richness of bacteria in the skin, gills, stomach, foregut, and hindgut were 3.06, 0.94, and 23.00; 2.97, 0.92, and 19.67; 3.44, 0.93, and 31.33; 3.16, 0.93, and 23.50; and 3.30, 0.95, and 26.00 in low weight (LW) and 3.11, 0.99, and 23.83; 3.10, 0.96, and 22.33; 3.45, 0.94, and 31.50; 3.23, 0.94, and 25.05; and 3.28, 0.95, and 25.33 in high weight (HW) , respectively. The Shannon diversity index, evenness, and richness of gills and richness of the foregut from HW (I. punctatus than that in LW . Clustering and principal component analysis (PCA) distinguished LW from HW I. punctatus in the skin, gills, stomach, foregut, and hindgut were 0.82, 0.78, 0.78, 0.61, and 0.73, respectively, suggesting significant differences in the bacterial flora between LW and HW . In addition, the Shannon diversity index and evenness and richness of microflora in the aquatic environment were 3.45, 0.99, and 31.40, indicating slightly lower diversity than that of the stomach flora. The Q-PCR results showed that the dominant skin microflora were Enterobacteriaceae and , the dominant microflora in the water, gills, and stomach were Enterobacteriaceae, ; and the dominant microflora in the foregut and hindgut were Enterobacteriaceae, Flavobacterium (10^1.97) on the skin, Enterobacteriaceae (10^7.69) in the stomach, 3.83) in the foregut, and ), and ) in the hindgut were significantly higher in HW than those in LW <0.05). Moreover, the total numbers of bacteria in the skin, gills, stomach, and foregut (I. punctatus. These results reveal an increasing trend for the numbers of microflora in HW . The Q-PCR results were analyzed by PCA to identify the correlations between the microflora in all samples. The results demonstrated that LW and HW were distinguished by PCA1; the skin microflora was associated with that on gills, the foregut microflora was associated with that in the hindgut, and the stomach microflora was associated with that in the water. These results indicate the unique flora of the skin, gills, and gastrointestinal tract in and show that the structure and abundance of microflora are complex in LW and HW .

Abstract: