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 62 毫秒
1.
Abstract. Diseases of bivalve molluscs characterized by the presence of prokaryotic intra-cytoplasmic inclusion bodies in epithelial cells are reviewed. The paper reports the history, clinical and pathological findings during hatchery epizootics of chlamydiosis in larval and postmetamorphic bay scallops, Argopecten irradians (Lamarck), and enzootic infection in wild, captive and cultured adult and juvenile bay scallops during a 15-year period (1972–1987) of surveillance for scallop diseases in the northeastern Atlantic coastal region of the United States. The disease was found in 44·4% of adult bay scallop laboratory accessions as an endemic disease without overt clinical signs or mortalities, and as a highly fatal epizootic disease with a rapid course in 20% of hatchery-reared larval and postmetamorphic bay scallop accessions. The pathogenesis and development of the chlamydial agent during hatchery epizootics are described. The importance of the congenital 'childhood' diseases of larval bay scallops and other species of bivalve molluscs is discussed.  相似文献   

2.
Feeding experiments using commonly-cultured algae were conducted with purple-hinge rock scallops, Hinnites multirugosus Gale, to suggest the application of these algae to hatchery culture of scallops. The uptake of finely divided particulate matter was also studied to ascertain the possible importance of detritus as a supplemental food for the rock scallop. A 1:1:1 mixture by culture volume of Tahitian Isochrysis, Tetraselmis suecica, and Dunaliella salina appeared to be superior as a diet for juvenile rock scallops. Significant growth also occurred in juvenile rock scallops fed T-Isochrysis, T. suecica, Isochrysis galbana, and Rhodomonas sp. Gymnodinium splendens, Monochrysis lutheri, and Dunaliella salina fed alone were poor foods for juvenile rock scallops. Finely divided particulate matter as radiolabeled abalone fecal matter was utilized as food. Significant radioactivity appeared in DNA, RNA, lipid, protein, carbohydrate, and free-reducing substances after one week providing evidence that particulate matter was incorporated into juvenile rock scallop metabolic pathways.  相似文献   

3.
Abstract. Over a 15-year period hatchery brown trout, Salmo trutta L., have been added 10 Lower Lough Erne, Northern Ireland to supplement declining native populations. Introductions have mainly comprised eyed ova and fingerlings, stocked into a number of rivers in the Erne drainage. Utilizing a natural genetic tag an electrophoretic assessment of the stocking programme was undertaken. The percentage hatchery genetic contribution in trout populations varied widely from river to river (19%-91%). Lough-caught brown trout (3+ and older) showed a substantial (21·5%) hatchery genetic component. Introgression of native-and hatchery stocks was evident. The resultant deleterious genetic consequences for the conservation of the unique Lough Erne brown trout gene pool arc discussed and alternative management strategies are proposed.  相似文献   

4.
The scallop Argopecten purpuratus is one of themajor resources of commercial importance in Chilean aquaculture. One of themajor limiting factors for the culture of this species has been mass mortalityoccurring during production of juvenile seed organisms where massmortality of veliger larvae has been attributed to the presence of pathogenicbacteria in scallops and hatchery systems. Bacteriological studies havedemonstrated that in addition to bacterial pathogens, beneficial bacterialspecies capable of improving scallop larval survival may also be isolated fromscallops and hatchery systems. Research has been carried out on thedetermination of the feasibility of implementing beneficial bacteria in thecontrol of culture pathogens, thus reducing the need for chemotherapeuticmethods. The present review analyzes bacteriological research data on thedifferent roles of bacteria associated with scallop culture and discussesrecentdata on the implementation of beneficial bacteria in biological control ofpathogens in larval mass cultures of Argopectenpurpuratus.  相似文献   

5.

Optimizing the release density and size of juvenile commercial species for local ecosystems is a critical issue that should be considered when countering predation impacts. To ascertain whether mariculture production of the Japanese scallop (Mizuhopecten yessoensis) could be enhanced by modifying releasing practices, we experimentally investigated the effects of density and size of scallop seeds on their survival in the presence of two sea star species, Asterias amurensis and Distolasterias nipon, with different predation capacities. Under current mariculture practices, the juveniles are briefly exposed to air just before release; therefore, we also examined how air exposure stress increased the predation risk. Scallop survival in the presence of both sea stars increased by?>?20% by increasing scallop size from 30 to 50 mm. Increasing scallop density (range: 5 to 30 scallops m?2) increased each individual’s survival in the presence of A. amurensis but had no significant effect on predation by D. nipon. Therefore, the release of smaller quantities of large-sized scallops rather than larger quantities of small scallops is recommended to reduce D. nipon predation. In the presence of sea stars, especially by D. nipon, the predation impact on small scallops increased after just a few hours of air exposure, indicating that air exposure of juvenile scallops should be minimized. Our results will mitigate the economic cost of mariculture by facilitating the determination of optimal release conditions for juvenile scallops.

  相似文献   

6.
The great scallop, Pecten maximus is a potentialaquaculture species in Norway, but production to date has been low. Greatscallop landings in 2000 were 571 tonnes, exclusively from harvesting wildstocks, landed by divers. Approximately two million juveniles of 15mm shell height have been produced annually in a hatchery since1998, and distributed to farmers. Research projects on larvae and juvenilesinclude studies of various antibacterial treatments, improved culture systemdesigns and application of probiotics. Results from hanging cultures underdifferent environmental conditions indicate a strong correlation between lowtemperature and poor survival, and point out the importance of careful selectionof cultivation sites. Good growth potential of scallops in Norwegian waters hasbeen shown, and it is possible to reach market size of 10 mm shellheight in three to four years. Experiments with fences and other strategiesprotecting cultured scallops on the seabed from predation by crabs are inprogress.  相似文献   

7.
The escape or release of cultured and domesticated organisms into the wild poses a threat to the genetic integrity of natural populations. Based on data from 17 microsatellite loci, the genetic differentiation between wild and hatchery Oujiang color common carp Cyprinus carpio var. color was investigated, and its potential application for identifying the escapees of hatchery strains was assessed using Bayesian genetic assignment. No significant differences were observed between pooled hatchery and pooled wild populations in terms of allelic richness (A R), observed heterozygosity (H O), and inbreeding coefficient (F IS). Analysis of molecular variance and pairwise F ST comparisons suggested significant genetic differentiation between hatchery strains and between hatchery and wild populations, which was further confirmed by principal components analysis and Bayesian clustering analysis. Bayesian genetic alignment showed high self-assignment accuracy (ranging from 86.0 to 96.0%) in the original populations, demonstrating the ability of this technique to identify hatchery Oujiang color common carp escapees in the wild population.  相似文献   

8.
The growth and survival of the Zhikong scallop Chlamys farreri suspended in deep water of Haizhou Bay were studied from July 2007 to June 2008, and the biodeposition method was used to estimate the clearance rate of C. farreri under field conditions. Results showed that the scallop grew fast during all the culture time, with the exception of summer. The condition index of the scallop increased with time and reached the highest value in spring of the second year. The survival of scallops was 60.8 ± 3.9% at the end of this study, mortality occurring mainly during the summer and autumn of the first year. The clearance rate fluctuated obviously with season,with the highest value in September 2007, and the lowest value in March 2008. Factors accounting for variations in growth and clearance rate of scallops are also discussed.  相似文献   

9.
After more than 20 years of hatchery production of Asian seabass in Thailand, genetic information is still lacking for effective genetic management and a selective breeding programme. This study aimed to evaluate genetic status of existing hatchery populations and genetic consequences of a selective breeding attempt. We examined genetic relatedness in seven hatchery samples, including a selectively bred population (RACF‐F1), compared with three wild samples using 11 microsatellite loci. Genetic diversity and relatedness values within most hatchery samples, except for RACF‐F1, did not differ from those of wild populations (P > 0.05). RACF‐F1 had the lowest allelic diversity and effective population size (Ar = 6.99; Ne = 7.8) and highest relatedness values (mean rxy = 0.075–0.204). Pairwise ΦST values, principal component analysis and model‐based cluster analyses revealed three genetically distinct hatchery groups: Eastern Thailand (CHN, RACF, NSCF and SKCF), Southern Thailand (NICA) and the Andaman Sea (STCF). Results suggest that exiting domestic populations capture reasonable amount of genetic variation and can be useful for a base population for genetic improvement programmes. In addition, given the rapid increase in relatedness that we observed in one selectively bred population, we recommend using selection methods and hatchery practices that reduce variability in family contribution in the subsequent generations.  相似文献   

10.
This study provides for the first time an evaluation of the natural availability of scallop seeds along the coastal area of Taranto (Mediterranean Sea, Southern Italy). To select the best artificial collectors to harvest scallop seeds in this area, cylindrical collectors (Cyl) were compared to traditional ‘Japanese‐style onion bags’ (Bag) across three sites. Scallops represented 26.6% of total bivalve recruitment among all collectors (782 ± 331 ind. m?2). The most recruited scallops were Flexopecten glaber and Mimachlamys varia. The white (F. glaber) and black scallops (M. varia) were abundant at all three sites, while the queen scallop, Aequipecten opercularis, was only found at one site. Beyond the recruitment of scallops, numerous other potential commercial bivalve species were collected, including Limaria tuberculata, which was the most abundant bivalve species (33.3% of total recruitment). At all sites, Bag collectors had higher recruitment than Cyl collectors. Scallops recruited in artificial collectors exhibited a multicohort size distribution at most sites, suggesting potentially continuous reproductive activity in the scallop populations. F. glaber, M. varia and L. tuberculata could be good candidates to diversify the aquaculture production because of the availability of seed and their growth rate. Moreover, the farming of these bivalves integrates well with other forms of aquaculture (e.g. mussels), thus potentially offering farmers an additional source of income.  相似文献   

11.
Specimens taken from natural populations of the scallop, Euvola ziczac (L.), were mass spawned in order to produce an initial stock of parents for a selection experiment. The purpose of the present study was to improve scallop shell growth and to calculate the degree of heritability of this characteristic. At one year of age, the top 10‰ of the stock (i.e. the larger scallops) were segregated to create the selected line. An equal number of mean-sized scallops was used to create the control line. In the second generation, after 294 days in culture, the heritability values of the scallops were calculated. Heritability estimates fluctuated between 0.47 and 0.54 depending on the character investigated, i.e. shell length or shell height. The selected line was 5.5‰ longer and 4.5‰ higher than the control line, and 7.3‰ longer and 9.4‰ higher than the parental line.  相似文献   

12.
We investigated strategies to enhance populations of bay scallops,Argopecten irradians irradians (Lamarck, 1819), in a presumablyrecruitment-limited natural habitat. At present, the Niantic Riverestuary supports only a minor bay scallop population that is harvestedrecreationally. Three enhancement strategies were evaluated; (1)collection and redistribution of natural spatfall, (2) introduction andover-wintering of hatchery-reared stock into natural habitat to providenew spawning stock, and (3) over-wintering of hatchery-reared stock insuspension culture for creation of mobile spawner sanctuaries. Anassessment of natural bay scallop recruitment in the Niantic Riverconducted in 1997 indicated that few spat were found, they were widelydispersed within the river, and peak spawning occurred in late July1997. Direct re-seeding was evaluated as an enhancement measure byplanting hatchery-reared scallops ( 38 mm shell height) insmall-scale, 100-m2 plots at different times and densities.Time of planting and the inferred predation intensity were major factorsaffecting survival; whereas, planting density had no significant effect.Approximately 9,000 scallops (35–45 mm shell height), broadcastwithin an eelgrass bed in November 1997, had high over-winter survivaland underwent gametogenesis and spawning during 1998. Of 26,000 bayscallops ( 45 mm shell height) over-wintered in suspensionculture from 1998–1999, approximately 60–80%survived, and these scallops spawned in mobile sanctuaries, during thesummer of 1999. There is good potential for using aquacultural methodsfor enhancement of bay scallop populations when natural recruitment ispoor and habitat and environmental conditions are not limiting.  相似文献   

13.
Intraspecific hybridisation may result in hybrid offspring exhibiting superior (heterosis) or inferior (outbreeding depression) fitness relative to their parental populations. As both have been demonstrated in salmonids, consequences of interbreeding between divergent populations are relevant to their conservation. Atlantic salmon Salmo salar L. were extirpated from Lake Ontario by the late 19th Century due to anthropogenic causes. Multiple allopatric populations of hatchery‐reared Atlantic salmon are being stocked in an effort to re‐establish a self‐sustaining population. This study evaluated whether interbreeding between Sebago Lake (Maine) and LaHave River (Nova Scotia) individuals will result in heterosis or outbreeding depression in juveniles. This was accomplished through full‐factorial 2 × 2 mating crosses between the strains and comparing multiple fitness‐related traits between the cross types. Hybrid juveniles displayed no signs of outbreeding depression nor heterosis. Further studies on comparative fitness of backcross and F2 hybrids are recommended to assess potential consequences for this and similar restoration efforts.  相似文献   

14.
Abstract Stocking has had a considerable effect on wild brown trout, Salmo trutta L., populations throughout Europe. To elucidate this impact and to outline further management strategies, the genetic structure of 25 wild populations and five hatchery stocks from Czech Republic and Slovakia were analysed using mitochondrial (control region) and nuclear DNA (microsatellites, LDH‐C1*) markers. Stocking practices have caused massive hybridisation between the Atlantic and Danube brown trout strains in the central Danube basin and have lead to a loss of among‐population divergence in Slovakia and the eastern part of Czech Republic. Comparison with studies from neighbouring countries revealed substantial differences in haplotype, allele frequencies and genetic diversity across Central Europe. Differences in stocking management and origin of breeding stocks appear to be crucial factors for the spatial variability of the genetic structure of brown trout.  相似文献   

15.
The effects of transfers and introductions of bivalue molluscs are alwaysmore or less unpredictable. Moving scallops, there is a risk of introducingpathogenic agents or of disturbing the balance between potentiallypathogenic agents and host species in the recipient ecosystem. Risk is noteliminated by merely following official regulations. Some factors which maybe important in order to assess risk, and to choose the level of risk we arewilling to accept, are: The existence of ``stowaways', and the action of mechanical vectors.One organism may carry another, and it is seems impossible to obtain a``clean' organism, in spite of long quarantines. The biological vector function. There may be unknown reservoirs,intermediate or alternative hosts of pathogenic agents in the ``new'environment. An introduced species may also carry potentially pathogenicagents into a new ecosystem. The often lacking knowledge concerning epizootiology. Life cycles ofmany pathogenic agents are poorly known, as are the infectious dose ofagent, influence of environmental factors on disease, etc. The diagnostic tools, and the ``human factor' in diagnostics. Methodsare often not sensitive enough to detect a pathogenic agent in a carrierstate, or immediately after the agent has entered the host, or at a lowprevalence/how intensity level. It is also important that personnel aresufficiently trained to do the diagnostic work. The official priority of disease control. There are no notifiablediseases of scallops. EC regulations, and the ``one area/one agent/one bivalve species'management. National and international trade, including illegal transport of livebivalves.Considering these factors enables a better focus on the riskfactors and the assessment of risks associated with introductions andtransfers of scallops. Consideration may also help to clarify the scientificlevel of knowledge and experience required to handle scallop diseases, andfocus on practical problems in scallop health control.  相似文献   

16.
Sympatric populations of the hermaphroditic scallop, Pecten fumatus Reeve, and of the dioecious scallop, Chlamys (Mimachlamys) asperrima (Lamarck), from Jervis Bay, New South Wales, Australia, were sampled between October 1991 and December 1994. Over the first 2 years, 5.1% of adult P. fumatus and 4.5% of adult C. asperrima were infected with a trematode, Bucephalus sp., that causes parasitic castration. A significant increase in the numbers of infected scallops occurred in spring 1993, teaching 63% in P. fumatus and 24% in C asperrima in May and March 1994, respectively. The prevalence of infection increased with scallop size, reaching 66% in P. fumatus greater than 80 mm in shell height and 40% in C. asperrima greater than 75 mm in 1994. Seasonal and interannual variations in parasitism for the P. fumatus recorded over a continuous period of 5 years in Jervis Bay are discussed, as are interspecies differences and the potential impact of the parasitic castration on reproductive potential and marketability of P. fumatus and C. asperrima.  相似文献   

17.
    相似文献   

18.
Low salinity is one of important environmental factors which often led to mass mortality of the noble scallop Chlamys nobilis cultivated in the South coast of China. It is well known that enzymic system and non‐enzymic system both play crucial roles in all living organisms against severe environments. To investigate how change about enzymic system and non‐enzymic system in the stenohaline marine bivalve under low salinity stress, an acute challenge lasting 48 hr was conducted using golden and brown noble scallops in the present study. The serine proteinase inhibitor from the noble scallop (CnSPI) was first cloned and expressed in different tissues. After low salinity stress, the gene expression levels were determined in haemocytes and compared between golden and brown scallops. Meanwhile, total carotenoids content (TCC) in adductor, superoxide dismutase (SOD) enzymatic activity and methylenedioxyamphetamine (MDA) content in gill and haemocytes were also determined and compared between the two colours scallops. Results showed that the CnSPI gene expression levels were significantly decreased after low salinity stress, and the golden scallops had higher gene expression levels than brown scallops (p < .05) at most times. Moreover, after low salinity stress, TCC, SOD enzymatic activity and MDA content also fluctuated, and the golden scallops contained higher TCC and SOD, but lower MDA than the brown ones. The present results indicated that enzymic system and non‐enzymic system were both changed under low salinity stress in the noble scallop and significantly different responses to the stress existed between golden and brown individuals. The SPI gene and carotenoids (CAR) both play a resistant role to low salinity stress in the noble scallop.  相似文献   

19.
Saroma Lake is the southernmost lagoon exhibiting seasonal sea ice coverage in the Northern hemisphere and one of the most important aquaculture areas for Japanese scallops (Mizuhopecten yessoensis). Under conditions of adequate food and appropriate temperature, scallops grow well from the time of ice melting in April to harvesting starting in July. However, over the past decade, Saroma Lake frequently has not been completely covered by ice in winter, and the production of Japanese scallops has shown significant changes. Therefore, this study integrated data from satellite remote sensing, buoys, and in situ observations with climatic events [the winter East Asian Monsoon (EAM) and El Niño/La Niña–Southern Oscillation events] to investigate the impact of ice coverage variations on scallop growth in Saroma Lake between 2007 and 2015. Daily ice conditions were detected using Moderate Resolution Imaging Spectroradiometer false colour images and an unsupervised classification method. The results indicated that EAM strongly influenced the ice coverage variation in Saroma Lake through their effects on temperature during winter. Ice coverage variations show a strong correlation with water temperature and spring phytoplankton blooms, which are the two most important environmental factors for scallop growth. In addition, extreme climate events could cause water temperature anomalies (as in 2015) which are unfavourable for scallop growth. Monitoring ice conditions should be considered when developing plans and management strategies for scallop aquaculture in Saroma Lake.  相似文献   

20.
The genetic variations of rohu (Labeo rohita, Hamilton) sampled from five hatchery populations (Arabpur, Brahmaputra, Comilla, Kishorganj and Natore) and three major river populations (the Halda, the Jamuna and the Padma) were analysed by allozyme electrophoresis. Ten enzymes encoded by 11 loci were screened, and six were polymorphic. Alleles at three loci (Est‐1*, Gpi‐1* and Gpi‐2*) proved variable for hatchery and river populations, and the Mdh‐2* locus exhibited heterozygous genotypes for river populations only. Polymorphic loci per population (27.3±5.3%), heterozygous loci per individual (15.5±1.2%) and relative gene diversity (0.27±0.08) in river populations were higher than those for hatchery populations (25.5±1.8%, 10.7±1.6% and 0.25±0.01 respectively). Also, the observed heterozygosity (Ho) and expected heterozygosity (He) (0.09±0.03 and 0.14±0.04 respectively) in river populations were higher than those in hatchery populations (0.08±0.01 and 0.11±0.01 respectively). The lower levels of genetic variability in hatchery populations suggested the occurrence of inbreeding and/or genetic drift. The pairwise population differentiation (FST) values showed a lower level of genetic differentiation between hatchery and river population pairs. The unweighted pair‐group method with arithmetic mean dendrogram of Nei's genetic distances showed a relationship between the genetic distance and geographic distance. The populations were clustered into three groups: the Padma in one group, the Halda in second group and the Jamuna, including five hatcheries, in the third group. Highly diversified rohu individuals were observed in the Padma and Halda Rivers, whereas less genetically variable individuals were found in the Jamuna River and five hatcheries. These findings can be useful for rohu hatchery propagation to enhance the sustainable aquaculture production.  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