Differential study of the Parabramis pekinensis intestinal microbiota according to different gonad development stages

To investigate the differences in gut bacterial community of Parabramis pekinensis at different growth stages, we collected wild P. pekinensis from the Jingjiang region of the Yangtze River, and detected the intestinal microflora structure using high-throughput sequencing technology. Results show that during stage I the dominant bacteria were Proteobacteria, Actinobacteria, and Firmicutes. During stage II, the proportion of Proteobacteria and Actinobacteria decreased, while the proportion of Firmicutes and Fusobacteria increased, especially Clostridium and Cetobacteria increased significantly. During stage III, Cetobacterium had a dominant position, while the proportion of Firmicutes decreased slightly. In stage IV, the male and female fish showed obvious differences. In the female gut, the proportion of Proteobacteria increased to the first place, while Fusobacteria decreased to the second place. In the male fish, the proportion of Fusobacteria dropped to the fifth, especially that of Cetobacterium decreased significantly, and that of Verrucomicrobia increased. In stage V, the proportion of Fusobacteria increased again to the first place, while Proteobacteria did not decrease significantly in the female gut. The gut bacterial community in males changed into a structure similar to stage I. In stage VI, the gut bacterial community in both females and males changed into a structure similar to stage I. There were significant differences in the intestinal microflora structure of P. pekinensis at different gonad development stages and sexes. To some extent, the changes in intestinal microflora structure reflect the changes in the nutritional requirements of P. pekinensis.

     

In vitro selection and characterization of putative probiotics isolated from the gut of Acipenser baerii (Brandt, 1869)

To select and characterize potential probiotic bacteria from the gut microbiota of Siberian sturgeon (Acipenser baerii), 129 strains isolated from the hindgut were screened for antagonistic activity against five fish pathogens. Ten isolates showed antagonism towards three or more pathogens. Nine of these isolates were Gram‐positive, belonging to Lactococcus (seven) and Bacillus (two), and a single strain belonging to the Gram‐negative Citrobacter. These inhibitory isolates were identified using genetic, phentotypic and biochemical traits, and further characterized by in vitro tests assessing the adhesion and growth in mucus and resistance to gastric and intestinal fluids. The candidate probiotics were determined to be non‐pathogenic through an in vivo study. Based on these assays, Lactococcus lactis ssp. lactis STG45 and STG81 showed the broadest inhibitory potential, a high viability in simulated gastrointestinal juice and the highest adhesion capacity to mucus. They were therefore selected as the most promising candidate probiotics. This is the first study screening probiotics among the gut microflora of Siberian sturgeon.     

Effect of Arthrospira supplementation on Oreochromis niloticus gut microbiota and flesh quality

Supplementing fish feed with Arthrospira platensis has several beneficial effects, such as improved growth, survival and feed conversion, but little is known about how it affects gut microbiota or flesh quality. In this trial, feed with 3% A. platensis was given to Oreochromis niloticus (SPR, spirulina supplemented) over a period of 50 days and their gut microbiota and flesh quality were compared with controls (CTRs, no supplementation). Average daily growth was higher in SPR fish (p < 0.05). Regarding microbiota, a total of 5,470,272 readings (individuals) were obtained from 16 gut samples (n = 8 CTR, n = 8 SPR), with a gamma diversity of 1,563 species but no significant differences were found between treatments. Among the high inter‐individual variability found, some individual microbiota were dominated by Proteobacteria (36.6%) and Fusobacteria (32.9%) and others more by Actinobacteria (37%). Regarding flesh quality, significant differences were observed in flesh colour post‐mortem (a*, b* and chroma) (p < 0.05), with higher reflectance in the range of 470–500 and 620–670 nm in SPR tilapia, which corresponds with the reflectance range of β‐carotene and phycocyanin. However, rigor mortis was resolved earlier in SPR fish (p < 0.05), which suggests a shorter shelf life. Adding 3% of A. platensis in O. niloticus diet can improve growth and flesh colour and does not appear to modify intestinal microbiota.     

中华鲟血清卵黄蛋白原水平的初步观察

通过碱不稳定性蛋白结合磷法测定不同年龄中华鲟(Acipenser sinensis)血清中磷含量,以磷的含量变化反映卵黄蛋白原(VTG)变化情况。实验鱼为人工养殖0.5、1、2、3、4、5、6、8、9、10龄中华鲟和野生成熟中华鲟,共81尾,其中8尾野生雌鱼在人工繁殖前后各取样2~4次,共测97个血液样本。结果显示:低龄中华鲟VTG含量较低,最低值在5龄,含磷量为(4.6±1.6)mg/L,5龄后增加,成熟后达到最大,含磷量为(52.0±4.5)mg/L。在性腺不同发育时期,雌性个体在Ⅱ~Ⅴ期VTG的含量增加,Ⅱ~Ⅲ期增加速度较快,随后变缓,Ⅴ期达到最高水平,Ⅵ期降低;而雄性个体在Ⅱ~Ⅳ期VTG的增加量很少,Ⅳ期达到最高水平,含磷量为(28.7±12.2)mg/L。繁殖雌鱼产前VTG含量最高,含磷量为(62.5±8.7)mg/L,产后低于产前。此外,发现产后鲟鱼卵巢液中含量低于其血清中含量,但高于其他年龄组血清中的水平。本实验表明淡水养殖的中华鲟有可能达到性成熟。     

长江江苏溆浦段2015 年发现中华鲟野生幼鱼的形态和分子鉴定

在葛洲坝下中华鲟(Acipenser sinensis)产卵场连续两年未监测到自然繁殖的情况下,2015年6月在江苏溆浦段发现15尾疑似中华鲟幼鱼。本研究通过形态学和分子生物学方法对该15尾幼鲟进行鉴定。形态学度量结果显示,除1尾个体外,新发现的14尾幼鲟与历史记载的中华鲟野生幼鱼生物学性状完全一致,但其体长和体重低于历史同期出现在该区域的中华鲟。同时采用11个多态微卫星位点,对15尾幼鲟样本和分布于我国的3种鲟鱼,包括30尾中华鲟(A.sinensis)、39尾达氏鲟(A.dabryanus)和33尾施氏鲟(A.dabryanus)进行遗传分析,发现这15尾幼鲟与中华鲟的遗传距离最近(F_(st)=0.039,P0.05),其次为达氏鲟(F_(st)=0.108,P0.05),最远为施氏鲟(F_(st)=0.209,P0.05),从遗传和进化的角度判定该批幼鱼为中华鲟,该结果暗示中华鲟在葛洲坝下游极有可能找到了新的产卵场,为中华鲟的繁殖群体和幼鱼的种群监测提供了依据。遗传多样性分析显示,该批鱼的遗传多样性(SW=1.998)略低于野生中华鲟(SW=1.886),暗示中华鲟幼鱼遗传多样性水平降低,野生亲本的数量仍不容乐观。     

Timing of spawning in cultured and wild Atlantic salmon (Salmo salar) and brown trout (Salmo trutta) in the River Vosso, Norway

Spawning time and size of wild and nonnative cultured female Atlantic salmon (Salmo salar L.) were studied in the River Vosso, Norway. Cultured immigrants were smaller, and peak spawning occurred 21 and 26 days earlier relative to wild salmon in 1991 and 1992, respectively. It was calculated that hatching and initial feeding of offspring of cultured females peaked 12 and 9 days earlier in spring 1992 and 19 and 8 days earlier in spring 1993 relative to offspring of wild females. Spawning time of the cultured salmon is similar to most Norwegian salmon populations and to cultured fish in other streams. In the River Vosso it also overlaps with that of brown trout (Salmo trutta L.), which may increase hybridization. The early time of breeding in nonnative fish indicates local adaptation in this trait in wild salmon. The consequences of early breeding of cultured fish are unpredictable in relation to spring temperatures but probably reduce their relative breeding success. The smaller size may also reduce the success of cultured females.     

达氏鳇和施氏鲟生长差异群体肠道菌群特征

同塘生长差异常常导致鲟养殖产量受损,而肠道菌群是影响鱼类生长性能的关键因素之一。为揭示肠道菌群与鲟科鱼类个体生长差异之间的关系,本研究对同批次繁育、同条件养殖的生长速率差异大于体重50%的达氏鳇(Huso dauricus)和施氏鲟(Acipenser schrencki)群体进行了肠道菌群特征研究。结果表明,达氏鳇和施氏鲟肠道菌群多样性和组成在种属间及生长差异群体间均具有明显差异。其中,生长快速达氏鳇群体(LH)肠道优势菌属为鞘氨醇单胞菌属(Sphingomonas,67.0%),生长慢速达氏鳇群体(SH)肠道优势菌属为鞘氨醇单胞菌属(29.5%)和狭义梭菌属1 (Clostridium sensu stricto 1, 54.2%);而生长快速施氏鲟群体(LA)肠道优势菌属为鞘氨醇单胞菌属(33.5%)和鲸杆菌属(Cetobacterium,38.1%),生长中速施氏鲟群体(MA)肠道优势菌属为鞘氨醇单胞菌属(42.6%)、狭义梭菌属1(14.3%)和鲸杆菌属(33.0%)。鞘氨醇单胞菌属和梭菌科(Clostridiaceae)细菌是不同生长速率鲟肠道中的主要差异类群。综上可知,鲟...     

Nutritional comparison in muscle of wild,pond and factory cultured Japanese flounder (Paralichthys olivaceus) adults

Muscle proximate composition, amino acid profiles, fatty acid compositions and selected minerals of wild, pond and factory cultured Japanese flounder adults were compared in this study to elucidate their nutritive values and dietary nutrition requirements. Wild and pond cultured Japanese flounder flesh had higher crude proteins, but crude lipid contents of factory cultured fish were 3.8~4.0 fold greater. Major amino acids in Japanese flounder were aspartic acid, glutamic acid and lysine. Wild fish had higher levels of total amino acids, essential amino acids, nonessential amino acids and half‐essential amino acids and the contents in pond cultured samples were similar. Arachidonic acids (ARA), eicosapentaenoic acids (EPA), docosahexaenoic acids (DHA), polyunsaturated fatty acids (PUFA), DHA + EPA and n–3 PUFA in wild Japanese flounder were significantly higher than that in factory cultured fish, whereas fatty acid levels were close between pond cultured and wild fish. Japanese flounder were rich in zinc, iron and selenium, but poor in copper, chromium and nickel. Results indicated wild Japanese flounder had higher nutritional value and better meat quality, but the nutritional compositions of pond cultured fish were close to wild Japanese flounder, which suggested that pond culture of Japanese flounder offers broad application prospects.     

Habitat use and population structure of four native minnows (family Cyprinidae) in the upper Missouri and lower Yellowstone rivers, North Dakota (USA)

Abstract – In 1997 and 1998, sampling was conducted on the Missouri and Yellowstone rivers, North Dakota, to obtain information on the distribution, abundance, and habitat use of the flathead chub (Platygobio gracilis Richardson), sicklefin chub (Macrhybopsis meeki Jordan & Evermann), sturgeon chub (Macrhybopsis gelida Girard), and western silvery minnow (Hybognathus argyritis Girard), four declining fish species (family Cyprinidae) native to the Missouri River basin, USA. The study area consisted of four distinct river segments near the confluence of the Missouri and Yellowstone rivers – three moderately altered segments that were influenced by a main‐stem dam and one quasi‐natural segment. One moderately altered segment was located at the confluence of the two rivers (mixing‐zone segment (MZS)). The other two moderately altered segments were in the Missouri River adjacent to the MZS and extended up‐river (above‐confluence segment (ACS)) and down‐river (below‐confluence segment (BCS)) from this segment. The quasi‐natural segment (Yellowstone River segment (YRS)) extended up‐river from the MZS in the Yellowstone River. Catch rates with the trawl for sicklefin chub and sturgeon chub and catch rates with the bag seine for flathead chub and western silvery minnow were highest in the BCS and YRS. Most sicklefin and sturgeon chubs were captured in the deep, high‐velocity main channel habitat with the trawl (sicklefin chub, 97%; sturgeon chub, 85%), whereas most flathead chub and western silvery minnow were captured in the shallow, low‐velocity channel border habitat with the bag seine (flathead chub, 99%; western silvery minnow, 98%). Best‐fit regression models correctly predicted the presence or absence of sicklefin chub, flathead chub, and western silvery minnow more than 80% of the time. Sturgeon chub presence and absence were predicted correctly 55% of the time. Best‐fit regression models fit to fish number data for flathead chub, sicklefin chub, and sturgeon chub and fish catch‐per‐unit‐effort (CPUE) data for flathead chub also provided good fits, with R² values ranging from 0.32 to 0.55 (P < 0.0001). The higher density and catch of the four native minnows in the YRS and BCS suggest that these two segments are better habitat than the ACS and MZS.     

Effects of dietary Radix Rehmanniae Preparata polysaccharides on the digestive enzymes,morphology, microbial communities and mucosal barrier function of the intestine of Luciobarbus capito

In this study, we assessed the effects of Radix Rehmanniae Preparata polysaccharides (RRPP) on the digestive enzymes, morphology, microbial communities and mucosal barrier function of the intestine of Luciobarbus capito. Fish were fed different amounts of RRPP (0, 0.05, 0.1, 0.2 and 0.4%) for 60 days. The results revealed that intestinal amylase and trypsin activities significantly increased after the 0.2% RRPP treatment (p < .05). Increases in intestinal fold height, wall thickness and fold density were observed in Luciobarbus capito fed an RRPP‐supplemented diet, and the best effect was observed in the proximal intestine. Sequencing of the bacterial 16S rRNA V4 region showed that dietary RRPP reduced intestinal microbial community richness and species diversity. Fusobacteria, Proteobacteria, Firmicutes and Verrucomicrobia were the dominant bacterial phyla in the intestine of Luciobarbus capito. Dietary RRPP affected the overall microbial community and increased the abundance of the genus Cetobacterium. Moreover, RRPP significantly upregulated the expression of occludin, zonula occludens (ZO)‐1 and claudin‐c in the intestine (p < .05). In summary, supplementing the diet of Luciobarbus capito with RRPP can improve digestive enzymes activities and intestinal morphology, modulate the microbial composition and enhance intestinal mucosal barrier function.     

Recent advances of genome mapping and marker‐assisted selection in aquaculture

Aquaculture is the fastest growing sector in agriculture. Substantial genetic gains have been achieved in a few cultured species using conventional selective breeding approaches. However, the majority of fish and shellfish species remain in their wild state. Due to the recognition of the enormous potential of marker‐assisted selection (MAS) to speed up genetic gain through early selection, aquaculture scientists have constructed linkage maps in over 40 species and mapped quantitative trait loci (QTL) for important traits in over 20 species since the 1990s. Although MAS and genomic selection (GS) have not been widely used in aquaculture, their application in breeding programmes is expected to be a fertile area of research. In this paper, I summarized the recent advances of linkage and QTL mapping, as well as MAS in aquaculture species. I also discussed the potentials of genome‐wide association studies (GWAS) and GS in aquaculture species.     

Opportunistic pathogens are abundant in the gut of cultured giant spiny frog (Paa spinosa)

Pathogen infection poses a serious threat to the survival and commercial quality of cultured Paa spinosa, which provide protection as a substitute for wild P. spinosa. The gut microbiota plays vital roles in host health and immunity. To provide guidance for preventing intestinal diseases of artificial P. spinosa culture, we compared gut microbiota compositions of wild and cultured P. spinosa using high‐throughput sequencing. A total of 11,526 operational taxonomic units (OTUs) were identified from 14,043 sequences from each sample. Cetobacterium, PW3 Bacteroides and some unidentified species from Bacteroidales, Rikenellaceae and Clostridiales were significantly increased in the gut microbiota from cultured P. spinosa, whereas Faecalibacterium and unidentified bacteria from Ruminococcaceae were significantly decreased in the gut microbiota from cultured P. spinosa. According to the gut microbiota composition, we hypothesized that the cultured P. spinosa in Jing'an would exhibit a higher risk of pathogenic infection than those in Cili. These results provided a method to forecast the pathogenic infection risk of cultured P. spinosa, which could guide the artificial culture of and prevent diseases in P. spinosa through gut microbiota.     

The loss of genetic diversity in Dabry's sturgeon (Acipenser dabryanus,Dumeril) as revealed by DNA fingerprinting

• 1. Dabry's sturgeon, a large, long‐lived migratory fish is endemic to the Yangtze River. Over‐fishing and habitat destruction have caused large‐scale declines in natural stocks in the last two decades.
• 2. Examining patterns of genetic diversity has become an integral component of many management plans for endangered species. DNA fingerprinting was applied to detect genetic diversity in Dabry's sturgeon collected in 1958–1959, 1980–1981 and 1998–1999.
• 3. Studies on direct genetic parameters (genetic variability, hypervariable loci and heterozygosity) and indirect parameters (band‐sharing coefficient and allelic frequency) showed that the continuous decline in wild populations has caused the loss of genetic diversity in present‐day sturgeon.
• 4. The present‐day populations have the lowest genetic variability; thus, effective management is needed to preserve genetic diversity.
• 5. A conservation strategy is urgently required, comprising artificial rearing facilities coupled with breeding management plans.

Copyright © 2003 John Wiley & Sons, Ltd.     

History,current status and prospects of sturgeon aquaculture in Russia

Since natural sturgeon populations have drastically declined, aquaculture of these valuable fish is important to meet the ever‐increasing demand for meat and caviar, thereby reducing the pressure on natural sturgeon resources. There are two directions in sturgeon aquaculture: controlled propagation for release and commercial farming. The controlled propagation supports the conservation of natural fish populations, while the commercial cultivation of sturgeons supplies the needs of the consumer market with the delicacy production of caviar (mainly). This review deals with the current status of the controlled propagation and stocking in the Volga‐Caspian basin and the commercial farming of sturgeons in Russia. The article also investigates the management of farmed broodstocks of sturgeons, which are used for obtaining seedlings and caviar. It is for sure that the active and continuous development of the two directions of sturgeon aquaculture will allow preserving these unique ancient fish on our planet until natural populations can be re‐established by self‐sustaining populations.     

Loss of genetic variability in the captive stocks of tambaqui,Colossoma macropomum (Cuvier, 1818), at breeding centres in Brazil,and their divergence from wild populations

The loss of variability in farmed populations and the risks of interactions with wild populations support the need for the genetic monitoring of species farmed throughout the world. In Brazil, the tambaqui is the most widely farmed native fish species. Despite this, there are no data on the pedigree of the farmed stocks, and the potential for interactions with wild populations in the Amazon basin has raised concerns with regard to the genetic variability of these stocks. The present study analysed sequences of the mitochondrial Control Region and 12 microsatellites to characterize the genetic variability of seven historically important commercial tambaqui breeding centres located in four different regions of Brazil, and compared these sequences with those obtained from individuals collected from a wild population. High levels of genetic diversity were found in the wild population, whereas genetic diversity was reduced in both markers in most captive populations, except for the broodstock located near the Amazon River. High F_ST and D_EST indices were recorded between the wild population and most of the captive stocks analysed. The drastic reduction in genetic diversity found in most captive stocks and the difference between these stocks and the wild population may have been the result of the small size of the founding populations and the absence of breeding management. The renewal of the broodstocks and the application of breeding management techniques are recommended. In the Amazon region, in addition, the use of broodstocks that are genetically very different from local wild populations should be avoided.     

Weaning methods using formulated feeds for snakehead (Channa striata and Channa micropeltes) larvae

The culture of snakehead fish (Channa striata and Channa micropeltes) in Vietnam is limited, and snakehead culture has been banned in Cambodia, because traditional practices include capture of fingerlings from the wild as seed, as well as capture of small‐size (also known as trash fish or low‐value) fish. As hatchery breeding technology has improved, we investigated the optimal weaning practices for these two species. Both laboratory experiments and farm trials were conducted. For C. striata, the optimal weaning procedure is to begin at 17 days after hatch (dah) and wean the fish at 10% replacement of live feed with formulated feed per day. However, for C. micropeltes, the optimal procedure is to wait until 40 dah to begin weaning and then to wean the fish with a 10% replacement of live feed with formulated feed every 3 days. These results should enable farmers to domesticate snakehead culture in Vietnam and Cambodia and eliminate reliance on fish captured from the wild as both seed and feed.     

Microbial communities associated with early stages of intensively reared orange‐spotted grouper (Epinephelus coioides)

The gut microbiota plays key roles in the health and general welfare of fish larvae, the present study characterized the bacterial communities associated with grouper Epinephelus coioides larvae during a period of 22 days post hatch (DPH) in an intensive hatchery using both cultivation‐based and cultivation‐independent approaches. Both approaches confirmed that bacteria were present in the gut of larvae before and after the onset of exogenous feeding, and the number of cultiviable bacteria increased gradually from 2 DPH to 22 DPH. A more complex bacterial profile was present in larvae fed fertilizer oyster eggs for 4 days (8 DPH), probably as a result of the onset of exogenous feeding. Interestingly, similar internal microbiota were observed in larvae fed fertilized oyster eggs for 4 days (8 DPH) and rotifers for 2 weeks (22 DPH), although different microbial communities were present in the two feeds. This might suggest that the gut environment of E. coioides larvae selects for a common microbiota, which is more closely related with the rearing water than the two feeds. Therefore, bacterial community of the rearing water may play a critical role in the establishment of gut microbiota of fish larvae and more attention should be paid to its practical modulation by using probiotics. In addition, some potentially beneficial bacteria, such as Lactococcus spp., were the major components of the microbiota associated with fertilized oyster eggs, while these bacteria were not detected in larvae samples.     

Phylogenetic analysis of intestinal bacteria of freshwater salmon Salmo salar and sea trout Salmo trutta trutta and diet

The microbial diversity of culturable intestinal microflora of wild freshwater salmonid fishes salmon Salmo salar and sea trout Salmo trutta trutta juveniles (0+ years old) from the same environmental conditions were investigated by means of molecular identification techniques and analysis of diet. Significant differences in the intestinal microbial diversity were observed in different fish species. The predominant group in the intestinal tract of the salmon comprised representatives of the Enterobacteriaceae family (23%), Plesiomonas (19.2%) and Carnobacterium (15.3%). Predominant microbiota in sea trout intestinal tract were Enterobacteriaceae (52%), Aeromonas (22%) and Pseudomonas (14%). The results show that Enterobacteriaceae were predominant in the intestinal tract of the salmon and the sea trout juveniles raised on diets of different compositions. However, molecular identification of the intestinal microbiota at the species or genus level revealed differences in these fish species. Bacteria in the hindgut of salmon included Pragia and Serratia. However, bacteria in the gut contents of sea trout from the Enterobacteriaceae family were Buttiauxella, Enterobacter, Moellerella, Pantoea, Rahnella and Tiedjeia arctica. A novel phylotype of T. arctica is harbored in the intestinal tract of wild salmon, and may correspond to a previously undescribed species.