首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 15 毫秒
1.
Seven samples, each consisting of approximately 50 Atlantic salmon, were collected from five marine farms in Norway. These farms reported to rear fish originating from the same commercial breed; however, all samples followed a unique route of production from breeder to marine farm via egg, fry and smolt producers. A group of farmed escapees (n=50) were also captured. Following genotyping with 18 microsatellite loci, the global FST was 0.083, and pair‐wise values were as high as 0.158. Four clusters, with varying degrees of genetic differentiation, were identified among samples from the farms, and the source of the escapees was identified successfully. It is suggested that the genetic differences observed among samples from the farms were created through the process of genetic drift, facilitated by parallel sub‐strains, extensive within‐strain selection and low to moderate numbers of adults contributing to batches of eggs. In conclusion, this study has demonstrated that genetic identification of escaped Atlantic salmon, back to the farm of origin, may be possible even when farms rear fish reported to originate from a single breeder.  相似文献   

2.
A simple, low-cost method for inducing ovulation in hatchery-held adult chinook salmon was developed. Use of this method resulted in an increase in the number of eggs collected, by circumventing losses due to prespawning mortality.One hundred and twenty 4-year-old chinook salmon which had returned to the Capilano hatchery prior to 1 October were used as a stock population. Three weeks before the peak spawning period, 36 fish were divided into two groups. The control group received two injections of 0.65% saline spaced 3 days apart. The test group received a 0.1-mg/kg SG-G100 (salmon gonadotropin) injection, followed on the third day by a 2.5-mg/kg SG-G100 injection. By Day 8, 73% of the treated group and 0% of the control group had ovulated. Prespawning mortality accounted for 22% of the treated fish and 83.4% of the control fish. Treatment resulted in a net gain of 16,000 eggs over the control. The second experiment began 3 days before the peak spawning period. The 32 fish which remained in the stock population were divided into three groups and received two injections 3 days apart. The two treatment groups received either 0.1 mg SG-G100/kg followed by 2.0 mg SG-100/kg, or 0.1 mg SG-G100/kg followed by 50.0 mg salmon pituitary extract (SPE)/kg. The control group was injected with 0.65% saline. By Day 8, 73% of the SPE group, 82% of the SG-G100 group, and 40% of the control group had ovulated. Treatment resulted in a net gain of 16,000 eggs for the SG-G100 group and 19,000 eggs for the SPE group over the control. No significant differences in egg size or percent survival to the eyed stage were found between test and control groups. The misjudgment of maturity led to the stripping of several fish before their eggs were completely ovulated. The factors leading to these partial ovulations are discussed.  相似文献   

3.
Abstract Singhi, the Indian catfish Heteropneustes fossilis , attained gonadal maturity repeatedly in a single spawning cycle by photothermal treatment. After the first spawning, maintenance at 30 C and 14 h light/10 h dark for 3 wk induced recruitment of the next batch of mature oocytes for subsequent spawnings. The number of eggs released declined with each spawning. However, fertilizability of the eggs was maintained until the fifth spawning. Mature fish were induced to spawn by D-Lys6 salmon gonadotropin-releasing hormone agonist administration. The dose of salmon gonadotropin-releasing hormone agonist for the second and subsequent spawnings was determined to be 25-fold less compared to the dose administered for the first spawning. Fish released the maximum number of eggs upon induction when they were maintained continuously at 30 C and 14 h light/10 h dark for 6 wk. The result obtained in the present study points to a possibility of obtaining multiple spawnings from those species of farmed fish which spawn once a year.  相似文献   

4.
Salmonid eggs were collected from spawning redds in the Norwegian rivers Alta, Gaula, and Driva in 1982. Their phosphoglucoisomerase (PGI; E.C. No. 5.3.1.9) patterns, as revealed by isoelectric focusing and histochemical staining, were compared to standard zymograms produced by Atlantic salmon (Salmo salar L.) and trout (S. trutta L.) white skeletal muscle extracts, and to the zymogram in salmon eggs of known origin. In salmon, the egg zymogram was identical with that of muscle. Two types of zymograms, identical with either salmon or trout muscle zymograms and thus regarded as species-determinants, were observed among the eggs from wild fish. Their proportions in the three rivers were as expected from current knowledge of species composition. The present findings are related to previous reports on PGI expression in salmonids. The PGI zymograms are probably diagnostic keys to species for eggs from Norwegian stream-dwelling salmonids, including Arctic char (Salvelinus alpinus L.). Some managemental implications of the present results are briefly discussed.  相似文献   

5.
Abstract. Bacteria and cutaneous ectoparasites associated with red spot disease (RSD) in sea mullet, Mugil cephalus L., from the Clarence and Richmond Rivers in north-east New South Wales were identified. Various bacteria, including Aeromonas spp., Alcaligenes spp., Pseudomonas spp. and Vibrio spp. were recovered from lesions designated erythematous dermatitis, necrotizing dermatitis and dermal ulcer, but no genus was consistently dominant in cultures from any of the lesion types. Vibrio anguillarum , previously proposed as the cause of RSD, was recovered from four of 37 lesions of erythematous dermatitis, none of 46 lesions of necrotizing dermatitis and eight of 36 dermal ulcers. Bacteria were recovered only rarely from liver and posterior kidney of diseased fish. These results suggest that none of the bacteria isolated is the primary cause of RSD. There was no evidence that cutaneous ectoparasites, including the digencan Prototransversotrema steeri , are significant in the pathogenesis of RSD in sea mullet. None were found on eight normal fish collected in the month preceding a major RSD outbreak. In the first 2 months of the outbreak, none were found on 18 fish with erythematous dermatitis, eight with dermal ulcers or 11 of 12 normal fish. A single digenean, morphologically consistent with P. steeri , was recovered from a normal fish collected during this latter period.  相似文献   

6.
Abstract. A Vibrio sp. causing the so-called 'Hitra disease' or coldwater vibriosis affecting brood stock Atlantic salmon, Salmo salar L., in Norway, is described by serotyping. Bacteria collected from moribund Atlantic salmon affected by 'Hitra disease' in various parts of Norway, were shown to represent a homogeneous group of marine vibrio. A formalized bacterin was made from one isolate. Vaccination of Atlantic salmon parr was carried out by direct immersion in a formalized bacterin prepared from a Vibrio sp. associated with 'Hitra-disease.' After 6 weeks the fish were revaccinated and transferred to net pens in the sea. Compared with unvaccinated controls, vaccinated fish demonstrated excellent protection when challenged 6 months later during a natural outbreak of coldwater vibriosis.  相似文献   

7.
Mouthrot infections (bacterial stomatitis) have a significant impact on the Atlantic salmon aquaculture industry in Western Canada due to economic losses and fish welfare. Bacteria isolated from lesions in the field have been identified as Tenacibaculum maritimum. Mouthrot is different to classical tenacibaculosis, which is most commonly associated with ulcerative lesions, frayed fins and tail rot. The marine fish pathogen T. maritimum is found worldwide; however, in Western Canada, the knowledge of the genetic profile of T. maritimum is limited. This study looked at increasing this knowledge by genotyping T. maritimum isolates collected from Atlantic salmon from farms in Western Canada. These genotypes were compared to other species of the genus Tenacibaculum, as well as other known sequence types within the species. The Western Canadian isolates belong to two new sequence types within the T. maritimum species. Phylogenetic analysis shows that the isolates form a distinct branch together with T. maritimum NCIMB 2154T separate from other Tenacibaculum type strains, and they are most closely related to strains from Norway and Chile.  相似文献   

8.
Egg strings of salmon lice, Lepeophtheirus salmonis (Krøyer 1837), collected from farmed and wild Atlantic salmon had similar length and number of eggs string?1. Egg production was investigated at water temperatures from 7.1 °C to 12.2 °C. A regression model indicated that at low temperatures egg strings were longer and had more eggs. Mean length of single eggs was significantly smaller and the percentage of non‐viable eggs in the strings was higher at 7.1 °C than at 12.2 °C. Adult females survived for up to 191 days at 7.2 °C, and during this period 11 pairs of egg strings were produced.  相似文献   

9.
Juvenile Atlantic salmon, sea trout and rainbow trout were used in an experiment in which two species in each tank were compared with controls of each species separately. Specific growth rate was best in the experimental groups where the two species were reared together. The theory was developed that social facilitation or moderate interaction could cause the better growht. No starvation as a result of competition was discovered in any group.  相似文献   

10.
Hydrated eggs obtained from a female milkfish, Chanos chanos, were artificially fertilized with the milt collected from a male injected with acetone-dried pituitaries of salmon. The fertilized eggs (1.1–1.25 mm in diameter) developed normally in seawater in basins and petri dishes at a salinity of 30–34‰, and successfully hatched in 25–28.5 hours at a temperature of 26.4–29.9°C. The yolk was completely absorbed in about 2.5 days and during this period many postlarvae died. A few larvae were reared up to 5 days but all died on the 6th day. Attempts were made to feed the postlarvae with freshly hatched trochophore larvae of oysters obtained from eggs artificially fertilized in the laboratory.  相似文献   

11.
The present study investigated the short-term (5 months) effect of replacing dietary marine oils with vegetable oils on the development of arteriosclerotic changes in the heart of Atlantic salmon, Salmo salar. The experiment was performed as a randomized observer-blinded and controlled trial. Farmed Atlantic salmon were randomly sampled from a study population containing 900 individuals. The salmon were divided into three groups and given diets with either 100% fish oil (Diet 1), a 50/50% mixture of fish oil and rapeseed oil (Diet 2) or 100% rapeseed oil (Diet 3). Ten sexually immature salmon from each dietary group were sampled in March and August 2002. Additionally, 47 sexually mature wild salmon were randomly collected in mid-September 2001. Serial histological sections were taken from the bulbus arteriosus and ventricle wall for histopathological evaluation of the coronary arteries and myocardium. No significant differences in mean coronary changes recorded by the main variable 'mean range lesion' (MRL) were detected between the groups in March or August. MRL increased significantly between March and August with Diet 2 (P < 0.01), was nearly significant with Diet 3 (P = 0.06) and was unchanged with Diet 1. This pattern coincided with the Diet 2 group having the highest increase in heart weight. MHC class II immunoreactive cells in the coronary changes were detected in sections from one individual in each group. Heart weight was the most dominant variable in the data set and explained linearly 15.5% of the variation in MRL. Body weight, fish length and heart weight were all significantly, positively and linearly correlated to MRL. The Diet 2 group had the highest growth rate and also exhibited a significant increase in MRL. The possible influence of diet composition on weight gain and MRL needs to be further elucidated. Increase in heart weight seems to be the dominating predictor of the appearance of MRL in Atlantic salmon. However, the present results cannot exclude the possibility that differences in fatty acid composition of fish feed can influence the development of arteriosclerotic changes in Atlantic salmon.  相似文献   

12.
The reproductive success of Lepeophtheirus salmonis settled on host and non‐host fish has been compared. Triplicate single species tanks of Atlantic salmon, marine three‐spined sticklebacks, saithe and Atlantic cod were exposed to 10 adult female L. salmonis per tank (n=30 lice per species). Adult female L. salmonis settlement and egg string production occurred only on salmon and cod, with no egg production occurring on saithe and three‐spined sticklebacks. The number of eggs in egg strings, hatching success of eggs and the survival of all larval stages to the copepodid stage were severely affected by the species of fish on which female L. salmonis had settled. L. salmonis settled on cod produced significantly fewer eggs, lower hatching rates and lower survival rates of larvae than females on Atlantic salmon. The production of egg strings by L. salmonis females infecting cod, which successfully hatch and moult through to the infective copepodid stage, albeit in small numbers, is discussed in terms of the implications to aquaculture and salmon and cod farming scenarios.  相似文献   

13.
The purpose of this study was to investigate the possibility of producing tetraploid fishes. Eggs of salmon (Salmo Salar) and rainbow trout (Salmo gairdneri) were treated with concentrations of cytochalasin B ranging from 1 μg/ml to 100 μg/ml for varying periods of time. All treated groups had higher death rates than untreated controls. If the treatment was started immediately after fertilization and before the eggs had swollen all eggs died. The highest frequency of mosaic embryos and polyploid cells was obtained when the treatment started 35–70 h° (hour-degrees) after fertilization and lasted until about the 4-cell stage of development. A dose of 10 μg/ml of cytochalasin B gave the most satisfactory results. This concentration was used for further work. Two batches of 6000 salmon eggs and several groups of rainbow trout eggs were treated and hatched. The hatchability was generally low while the control group had a normal hatchability. If some of the treated fish are eventually found to be tetraploids and fertile, they will be used to produce triploid offspring by crossing with normal diploid fish.  相似文献   

14.
Bacteria were isolated from the diseased eggs of two damselfish (Pomacentridae) species, Amphiprion clarkii and Amblyglyphidodon curacao . Healthy A. clarkii eggs were infected separately with four bacterial isolates from the diseased eggs, as well as with Vibrio parahaemolyticus and Listonella anguillarum. Amphiprion clarkii eggs exposed to Cura-d, an isolate from diseased A. curacao eggs, showed increased mortality compared to uninfected control eggs. The A. curacao eggs were infected separately with the same two isolates from diseased A. curacao eggs, and similarly, eggs exposed to isolate Cura-d also showed increased mortality compared to uninfected eggs. However, the increase in mortality associated with exposure to isolate Cura-d was most significant in A. clarkii eggs. A 16S rDNA comparative sequence analysis identified that isolate Cura-d was most similar to Pseudoalteromonas piscicida , a known fish pathogen. Both Cura-d and P. piscicida were found to be polarly flagellated, Gram-negative rods with an oxidative metabolism which grew on d-mannose, d-fructose, sucrose and maltose, but not on l-threonine. Based on these properties, it is proposed that Cura-d should be classified as P. piscicida strain Cura-d. It is concluded that the P. piscicida strain cura-d was associated with the increased mortality observed in A. clarkii eggs.  相似文献   

15.
The virulence of two Vibrio strains, previously isolated from diseased corkwing wrasse Symphodus melops and identified as V. tapetis and V. splendidus, to corkwing and goldsinny wrasse Ctenolabrus rupestris and to Atlantic salmon Salmo salar, was studied under laboratory conditions. Both bacteria were shown to be opportunistically pathogenic to corkwing wrasse, causing significantly higher mortality in the challenged groups than in the controls. Bacterial cultivation of kidney samples and re-isolation of V. tapetis and V. splendidus from most mortalities confirmed the two strains as the probable cause of mortality in the challenged groups. The control group also suffered relatively high mortality, but no specific pathogens that were suspected to be the main cause of death were isolated, other than a mixture of Vibrio spp. and, in the case of one individual, atypical Aeromonas salmonicida. Following injection challenge with both bacterial strains, no mortality was recorded in Atlantic salmon. In bath challenge trials with goldsinny wrasse, only slight mortality was observed in the challenged groups and the unchallenged control group. Bacterial examination showed that atypical Aeromonas salmonicida was the probable cause of death in both bath challenged and control groups of goldsinny wrasse, and no indication of infection by any Vibrio sp. was found.  相似文献   

16.
Four small identical tanks fed with power station effluent were each stocked with 10 × “1-group” plaice. The fish in each of the tanks were fed minced fish containing different binding agents. Bacteria were isolated from skin and intestinal samples of two fish taken from each tank. Five generic/group generic types were isolated from fish skin while ten types were isolated from fish intestines. Organisms belonging to the Enterobacteriaceae were isolated from both skin and intestines. The types isolated from intestines also included Aeromonas species (spp.). However, strict anaerobes were unable to be isolated.All intestinal bacteria were tested for their ability to grow on a minimal salt agar medium containing each of the binders as sole carbon source. There was no special relationship between the binder to which the isolates were exposed in the fish intestine and the binders which they could utilise as sole carbon sources. Few isolates could utilise hydroxypropyl-methyl cellulose.  相似文献   

17.
The sea louse (Caligus rogercresseyi) is the most significant parasitic pathogen in Chilean salmon farms, and it infects farmed salmon and native host fish. Fecundity is one of the most important parameters for understanding the population dynamics of a species; however, this information is scarce for this parasite. The fecundity of C. rogercresseyi females collected from native hosts (Eleginops maclovinus) captured near salmon farms in southern Chile was measured to evaluate the reproductive output of this parasite on this host fish. From June 2008 to May 2009, 212 specimens of E. maclovinus were examined. Each fish was measured, and all its parasites were collected, sorted and counted. Seventy‐nine ovigerous C. rogercresseyi females (OFs) were measured. Total body length, egg string length and total number of eggs per string were recorded for each parasite. Ovigerous females body length varied between 3.9 and 5.0 mm. Fecundity varied between 12 and 56 eggs string?1, and it was correlated with OF body length. Temporal variations in OF fecundity were explained by co‐variation in OF body length, but not by month. Ovigerous females on E. maclovinus were smaller and showed lower fecundity than OFs on farmed salmon. Our results suggest that native hosts play a secondary role in C. rogercresseyi egg production in Codigue bay.  相似文献   

18.
Extreme variability in abundance of California salmon populations is often ascribed to ocean conditions, yet relatively little is known about their marine life history. To investigate which ocean conditions influence their distribution and abundance, we surveyed juvenile Chinook salmon (Oncorhynchus tshawytscha) within the California Current (central California [37°30′N) to Newport, Oregon (44°00′N]) for a 2‐week period over three summers (2010–2012). At each station, we measured chlorophyll‐a as an indicator of primary productivity, acoustic‐based metrics of zooplankton density as an indicator of potential prey availability and physical characteristics such as bottom depth, temperature and salinity. We also measured fork lengths and collected genetic samples from each salmon that was caught. Genetic stock identification revealed that the majority of juvenile salmon were from the Central Valley and the Klamath Basin (91–98%). We constructed generalized logistic‐linear negative binomial hurdle models and chose the best model(s) using Akaike's Information Criterion (AIC) to determine which covariates influenced the salmon presence and, at locations where salmon were present, determined the variables that influenced their abundance. The probability of salmon presence was highest in shallower waters with a high chlorophyll‐a concentration and close to an individual's natal river. Catch abundance was primarily influenced by year, mean fork length and proximity to natal rivers. At the scale of sampling stations, presence and abundance were not related to acoustic indices of zooplankton density. In the weeks to months after ocean entry, California's juvenile Chinook salmon population appears to be primarily constrained to coastal waters near natal river outlets.  相似文献   

19.
Abstract Atlantic salmon, Salmo salar L., recreational fisheries in Norway are facing shorter seasons and harvest restrictions because of low adult migration runs. Private fishing‐right holders (landowners) are important stakeholders, being co‐managers of the stocks, owners of salmon habitat and suppliers of angling. Landowners saw measures addressing salmon farming and Gyrodactylus salaris (Malmberg) as the most important management actions to strengthen stocks and downplayed actions restricting their own activity or gain. The results showed a need to build knowledge and improve communication between landowners and river owner organisations about the effects of stocking, catch and release, and other management actions. Four distinct landowner types were identified, based on their objectives for the fishing right. The diversity in the landowner group suggests managing angling tourism will be challenging, and cooperation is required to manage salmon stocks. Policy instruments to facilitate cooperation are discussed for each landowner type.  相似文献   

20.
王会芳 《水产学报》2004,28(3):347-351
According to the salmon‘s(Oncorhynchus) biological character of return to its hatching river, adopting the method of transplant and releasing, 9839000 eyed eggs of the salmon were introduced (Oncorhynchu, keta, O.gorbuscha, O. kisutch, O. masou) from Japan, total 8409000 juvenile fish was hatched and cultivated for 11 years running from 1985 to 1996. total 127 returning and mature salmons were collected from 1987 to 1995. It proved that the salmon could exist in the Yellow Sea area and return to its releasing river.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号