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1.
《水生生物资源》1999,12(2):121-130
The French oyster farming industry relies almost exclusively on juveniles collected from the natural environment; the supply of spat produced by hatcheries is low, about 10 % of the industry's requirements. Development through selective breeding of oyster stocks which are better suited for aquaculture purposes, is likely to reverse this tendency since only hatcheries will be able to supply such animals. Scallop farming, which at present is poorly developed in France, relies exclusively on hatchery produced spat. Although hatchery technology is constantly being improved, significant production problems remain which must be solved before hatcheries become a major supplier of juveniles for the industry. This paper describes the present state of hatchery technology in France based on experimental results obtained with the great scallop Pecten maximus and the Pacific oyster Crassostrea gigas, over the past ten years. Compared to the great scallop, the Pacific oyster has higher D larva yields (60 % for C. gigas vs. 30 % for P. maximus) and a faster larval growth rate (10 μm·d−1 for C. gigas vs. 5 μm·d−1 for P. maximus). However, Pacific oysters have a greater heterogeneity during larval development and higher mortality rates (40 % for C. gigas vs. 25 % for P. maximus) which produce lower overall yields of pediveliger larvae ready-to-set for Pacific oysters (15 %) compared to the great scallop (30 %). Development of continuous larval and post-larval culture methods along with development of continuous phytoplankton technology offers one of the most promising methods to improve molluscan hatchery techniques.  相似文献   

2.
We used mitochondrial (mt) DNA barcoding to evaluate the species diversity of oysters sampled from the coast of Okinawa Island, Japan. Our analysis revealed the presence of a hitherto-unrecognized population of the Portuguese oyster Crassostrea angulata, a putative species closely related to the Pacific oyster C. gigas. Forty-eight Okinawan oyster specimens were collected and subjected to species diagnosis trials based on mtDNA barcodes. Of the 30 Crassostrea specimens, 17 were identified as C. angulata, seven as C. gigas and six as C. bilineata (syn. C. iredalei). The remaining 18 Saccostrea specimens formed several divergent clades in phylogenetic trees, although they could not be identified to species level because of the confounding taxonomy of the Saccostrea species complex. Our results stress the necessity for reviewing the species diversity of Okinawan oysters.  相似文献   

3.
Light spatfalls of the Pacific oyster, Crassostrea gigas, have occurred in the estuaries of the Rivers Exe, Teign and Dart (Devon) and in the Menai Strait (Gwynedd), near to sites of commercial cultivation of this species. Comparisons of the sizes of the naturally settled oysters with hatchery oysters suggests that the spat from the River Teign and Menai Strait settled in 1989 and 1990. The springs and summers of these years were exceptionally warm with mean monthly air temperatures 0.8°-1.3°C above the 1951–1980 average for the period April to August. Although sitings of Pacific oyster spat were made in Loch Sween and Emsworth Harbour over 20 years ago, there is no evidence that self-sustaining populations have developed. The spatfalls which occurred in some coastal waters of Devon and Gwynedd in 1989 and 1990 are unlikely to sustain natural fisheries and are likely to die out as did the Portuguese oysters which occasionally settled in the River Blackwater, Essex.  相似文献   

4.
In order to develop an appropriate natural resource management policy, it is important to elucidate the cryptic habitats of species. Oyster species are likely to have such unrecognized habitats owing to the difficulty involved in morphological species identification. In this study, we discovered a novel cryptic habitat of the Kumamoto oyster Crassostrea sikamea, a sibling species of the Pacific oyster C. gigas, in Korean waters. We collected 50 oyster samples from Suncheon Bay, located in the southern Korean Peninsula, among which 20 individuals of C. sikamea, 29 of C. gigas, and one C. sikamea/C. gigas hybrid were identified based on mitochondrial and nuclear DNA markers. There were no significant differences in shell morphology between the two species, which is consistent with how difficult it is to delineate them based on their shell features. Our identification of this novel C. sikamea habitat should help to improve the resource management of East Asian oysters.  相似文献   

5.
In order to study the possibility of gaining commercial benefit from culturing an excess of one sex of the Pacific oyster (Crassostrea gigas), comparative data on the growth rate and condition of male and female oysters are reported. Historically, measurement of sex‐specific growth rate in oysters has been overlooked or confounded by protandric sex. The recent conclusion that the sex ratio of Pacific oysters is predominantly under genetic rather than environmental control introduces the possibility of manipulating sex ratio for commercial gain if they exhibit asynchronous sex‐specific growth rates. Pacific oysters were cultured intertidally in Smoky Bay, south Australia. The observations, made over the 7‐month gametogenic cycle from August to February to ensure no sex reversal, were of growth rates of male and female oysters and ambient chlorophyll a concentrations. Mean shell growth of female oysters was significantly faster than that of males (4.5 ± 3.3 compared with 3.8 ± 3.2 μm day?1 mm?1 total length). Sex‐specific asymmetries in length and weight were generally significant and increased in magnitude during the 7‐month study period, suggesting potential commercial benefits from increasing the proportion of cultured female oysters. The fastest increase in the sex‐specific disparity in growth and condition came after the October chlorophyll a peak, suggesting that females utilize blooms more efficiently than males. Our results compare favourably with methods currently used to increase oyster growth (e.g. triploidy can provide growth gains of 13–51%).  相似文献   

6.
Pacific oysters (Crassostrea gigas) were first observed in the Dutch Wadden Sea near Texel in 1983. The population increased slowly in the beginning but grew exponentially from the mid-1990s onwards, although now some stabilisation seems to be occurring. They occur on a variety of substrates such as mussel beds (Mytilus edulis), shell banks, dikes and poles. After initial settlement spat may fall on older individuals and congregate to dense clumps and subsequently form reefs. Individual Pacific oysters grow 3–4 cm long in their first year and 2–3 cm in their second year. Many mussel beds (Mytilus edulis) are slowly taken over by Pacific oysters, but there are also several reports of mussel spat settling on Pacific oyster reefs. This might in the end result in combined reefs. Successful Pacific oyster spat fall seems to be related to high summer temperatures, but also after mild summers much spat can be found on old (Pacific oyster) shells. Predation is of limited importance. Mortality factors are unknown, but every now and then unexplained mass mortality occurs. The gradual spread of the Pacific oyster in the Dutch Wadden Sea is documented in the first instance based on historical and anecdotal information. At the start of the more in-depth investigation in 2002, Pacific oysters of all size classes were already present near Texel. Near Ameland the development could be followed from the first observed settlement. On dense reefs each square metre may contain more than 500 adult Pacific oysters, weighing more than 100 kg per m2 fresh weight.  相似文献   

7.
The effects of starvation on biochemical composition and gametogenesis were investigated in the Pacific oyster Crassostrea gigas. Histological analysis, combined with oocyte examination and measurements of protein, glycogen and lipid levels and RNA/DNA ratio from gonad, adductor muscle and mantle tissue of each sex were performed. In the starved groups, C. gigas showed gonad development, but the progress was delayed during the experiment. Glycogen was the first substrate used by C. gigas for dealing with lack of food. While glycogen was rapidly consumed, protein and lipid contents decreased gradually. A decrease in the RNA/DNA ratio in the starved groups in all the body components was found during starvation, illustrating that RNA/DNA ratio was a valid indicator of nutritional condition in C. gigas. A significant increase in water and ash contents and a corresponding decrease in condition index were observed in the starved groups, showing that the water and ash content and condition index were related to the usage of glycogen, lipid and protein reserves in body composition. During starvation, energy reserves were mobilized for survival and gonad development, but spawning was arrested. The information obtained in this study is useful for broodstock management in the Pacific oyster industry.  相似文献   

8.
This is the first evaluation of growth and survival of spat of the Cortez oyster Crassostrea corteziensis (Hertlein) produced under controlled conditions in a coastal area in the state of Sonora, Mexico for aquaculture purposes. A suspended culture technique, used for the Pacific oyster C. gigas, was used. The Cortez oyster has an isometric shell growth during the first 13 months, reaching 71.3±1.9 mm length, 52.6±1.3 mm thickness and 25.1±0.8 mm width. Allometric growth was found between total weight and length, thickness and width (survival was 70%). The relationships between particulate organic, inorganic material, chlorophyll a and environmental parameters with growth are described. Growth rates of C. corteziensis were affected by temperature with retardation at less than 18°C. For aquaculture purposes, it is recommended that spat be sowed after winter, and oyster harvest occur at the end of autumn. According to the von Bertalanffy equation, Cortez oysters would reach the traditional exploitation size of 65 mm (mean length) at harvest. Finally, the results of this study have shown that C. corteziensis is a good candidate for aquaculture projects in this region.  相似文献   

9.
Growth is an important aquaculture trait, which has been one of the most important traits for genetic improvement in aquatic species. Numerous fast‐growing domesticated aquaculture organisms are being cultured, but the physiological processes underlying growth remain largely unexplored. The Pacific oyster (Crassostrea gigas) is one of the most widely farmed bivalves. In order to improve the productivity traits, a fast‐growing selective strain of C. gigas was established. In this study, we compared physiological energetics of the fast‐growing selective strain and an unselected hatchery population of C. gigas under different conditions of temperature. Components of energy gain (clearance rates, ingestion rates, absorption efficiency and absorption rates), energy loss (metabolic rates) and resulting energy budget (scope for growth) were analysed at four temperatures (15, 20, 25 and 30°C). The results indicated that selective breeding oysters had a higher energy gain compared to unselected oysters, but the selected strain and hatchery population of oysters did not significantly differ in metabolic rates at all tested temperatures (p > 0.05). The enhanced energy gain resulted in almost two times higher scope for growth in selective breeding oysters compared with unselected oysters. Physiological characteristics of C. gigas were greatly affected by temperature and showed a fluctuation with the increase in temperatures. The selective breeding oysters outperformed those of hatchery population in growth performance by an increased energy gain along with a similar energy loss. This study provided insight into physiological energetics accounting for growth improvements in fast‐growing selective strain of C. gigas.  相似文献   

10.
In the present study, hybrid and inbred oysters were produced by factorial hybridization between two closely related species, the Pacific oyster Crassostrea gigas and the Portuguese oyster C. angulata. Tissues samples were used for the analysis of total lipid content (TLC) and fatty acid composition (FAC). In general, FAC but not TLC in hybrid oysters was significantly different from inbred oysters. Hybrid oysters have significantly lower ∑SFA composition but higher ∑PUFA composition than inbred oysters, with heterosis for ∑SFA, ∑MUFA and ∑PUFA of ?6.03%, ?6.53% and 14.31% respectively. Moreover, hybrid oysters have significantly higher EPA + DHA content and n3/n6 PUFA ratio than inbred oysters, indicating higher lipid nutritional quality than inbred oysters. Among them, the hybrid ♀ C. gigas × ♂ C. angulata appears to be the most nutritious. These results indicated that the lipid nutritional quality of oysters can be improved by hybridization.  相似文献   

11.
We investigated the early growth and reproduction of hatchery-produced Pacific oysters Crassostrea gigas raised in a suspended long-line facility in Gamakman Bay, off the south coast of Korea. In October 2009, 4?months after transplanting, shell length had increased from 27.4 (July) to 82.5?mm (October), and tissue weight had increased from 0.2 to 5.2?g, indicating that the oyster had reached a marketable size in this month. Histological studies indicated rapid gonad maturation, and the oysters spawned during August and October, with a peak in September. An enzyme-linked immunosorbent assay used to quantify egg biomass revealed that the oysters produced a relatively small quantity of eggs, ranging from 5.1?% (August) to 8.8?% (September) of their body weight. The low total carbohydrate reserve in the tissue recorded in August and September coincided with intense energy utilization due to spawning, while the protein maximum in September matched peak egg mass. Our results suggest that hatchery-produced seed could supply a portion of the spat required in Gamakman Bay as well as in other oyster culture grounds of Korea, where the oyster industry is facing a shortage in the supply of natural spat.  相似文献   

12.
In this study I investigated the seasonal occurrence of microzooplankton in the gut of the Pacific oyster Crassostrea gigas. Gut contents consisted of various microzooplankton, including tintinnid ciliates, dinoflagellates (Dinophysis spp.), copepods, copepod nauplii, bivalve larvae, and rotifers. Monthly variations in the abundance of protists (tintinnids and Dinophysis spp.) in the gut contents were significantly correlated with the variation in their abundances in the surrounding seawater, whereas this relationship was not significant with metazoans (copepods, copepod nauplii, and bivalve larvae). In laboratory experiments, oysters actively fed on ciliates. When oysters fed on ciliates labeled with a stable nitrogen isotope (15N), the 15N:total N ratio of the oyster tissues was significantly higher than that for oysters under a no-food condition, suggesting that oysters assimilate nitrogen of the ciliates into their body tissues. Based on these results, I conclude that microzooplankton forms an important food source for oysters, especially when other food sources such as phytoplankton are not abundant.  相似文献   

13.
The Pacific Oyster (Crassostrea gigas) has been grown in a shallow hypersaline pond, approximately 3 km2 in area. The pond is non-tidal and is the primary one of a series used in the manufacture of salt by evaporation.In the past, similar areas have been considered unsuitable for oyster cultivation: however, the growth rates recorded for C. gigas in this experiment were very high (maximum of 22.4 g/month live weight) and mortalities were less than 30% over the period of study (12 months).The successful cultivation of C. gigas in the pond appears to depend on water circulation caused by wind action and it is likely that similar non-tidal areas could be used for oyster farming.  相似文献   

14.
Shell length and tissue growth of Pacific oyster Crassostrea gigas integrated culture with Sea bass Lateolabrax japonicus were monitored during April–October 2010 in Ailian Bay, China. And also, the food sources of the oyster were analyzed and quantified by stable carbon and nitrogen isotope methods. Results showed that the increment of shell length and flesh dry weight of oyster cultured at cage area were greater than that at control area significantly (P < 0.05). Enrichment of δ13C and δ15N in oyster tissue at the cage area relative to the control area was significant (P < 0.05). Based on the simple linear mixing model, the contribution rate of the fish feces and waste fish feed to oyster was 29.27 and 5.59 %, respectively. This work demonstrates that the differences in growth performance of oyster between cage area and control area were resulted from the utilization of organic matter derived from fish aquaculture. Integrated filter-feeding bivalves culture with marine fish can reduce the environmental impact of organic waste from fish-farming activities.  相似文献   

15.
This study investigates the vulnerable period in postspawning Pacific oysters (Crassostrea gigas) through physiological and immunological assessments. After spawning, the oyster condition index reduced by 50% and required 70 days to recover to the prespawning level. The mantle glycogen reduced quickly while the reduction in tissue protein occurred slowly. The mantle tissue also lost more protein than gills. The analysis of adenylate energy charge indicated that oysters were stressed in the first 8 days after spawning. As a result of spawning, haemocyte phagocytosis was reduced and remained at a low level for 3 days. In contrast, the reduction of haemolymph antimicrobial activity did not occur until 3 days after spawning and continued to decline until day 8. This immunesuppression was not directly correlated to the changes in haemocyte density. Our study suggests that the first 8 days after spawning are a critical period for oyster survival due to the loss of energy and low immunity. This study further improves our understanding of the coincidence between spawning and summer mortality in oyster aquaculture.  相似文献   

16.
Temperature and quality of the available food are important factors that influence the physiology of oysters; however, the combined effects have not been well studied. We evaluated the impacts of the temperature and diet on the growth, survival and biochemical composition in the Pacific oyster Crassostrea gigas spat, cultured in the laboratory for 8 weeks at 23, 26, 29 and 32°C and fed Isochrysis sp.‐Pavlova lutheri (IP) and Dunaliella tertiolecta (Dt). The growth and biochemical composition showed a pattern, which changed in response to rising temperature. The shell length was significantly longer, in spat fed the IP diet, except at 32°C, where both diets produced poor growth results. The survival was <50% after 5 weeks at 32°C, whereas at all other temperatures it was >88%. High temperatures directly increased lipids and saturated fatty acids, while the proteins, carbohydrates and unsaturated fatty acids decreased. High temperatures achieved in the environment, as those reached on clear summer days during low tides, are an important stressor in oyster spat, especially when the quality of the available food is poor.  相似文献   

17.
The microalga Chaetoceros calcitrans was cultured with three concentrations of vitamin B12 (cyanocobalamin) to supplement the feed for the oyster Crassostrea gigas. In two additional assays, vitamins B12 and B9 (folic acid) were dissolved in the water to increase the methyl donors necessary for the one‐carbon cycle and DNA methylation. Microalgae did not present differences in their concentration of vitamins, and no correlation was found between the concentration of vitamin supplement and the vitamin concentration in oysters; however, changes in the expression of genes involved in the DNA methylation were found. The expression of proton‐coupled folate transporter (PCFT) was lower in oysters supplemented with Vit. B9. The expression of proton‐coupled folate transporter (PCFT) was lower in oysters supplemented with Vit. B9., however, the expression of genes implicated in the release of the methyl used to maintain methylation such as methionine synthase (MS) and DNMT1 expression was high, suggesting faster transportation of Vit. B9. The methylenetetrahydrofolate reductase (MTHFR), implicated in the reduction of folic acid, was lower in oysters supplemented with Vit. 9 and B12 dissolved in the water. DNA methyltransferase DNMT1A, involved in DNA maintenance, was higher in oyster supplemented with Vit. B9, but the expression of DNMT1B was not different. In conclusion, the supplementation with folic acid increases the expression of genes implicated in the maintenance of DNA methylation in C. gigas.  相似文献   

18.
《水生生物资源》2002,15(4):251-258
French mollusc production is based mainly on the Pacific cupped oyster, Crassostrea gigas. Since 1991, annual mass mortality of juveniles has been reported during summer months. These recurring episodes concern professionals who fear that like Portugese oyster, C. angulata, C. gigas could in turn disappear following one of these epizooties. Previously, bacteriological analysis of moribund oyster juveniles yielded an isolate of a Vibrio splendidus biovar II strain, named TNEMF6. This isolate was demonstrated to be pathogenic to Crassostrea gigas spat by experimental challenge. To study the association between summer oyster mortality and presence of TNEMF6 cluster strains, Vibrionaceae fauna were isolated from infected spat along the French Atlantic coast between 1997-1998. Strains related to V. splendidus biovar II were selected. Comparison with TNEMF6 was performed by classical biochemical tests and polymerase chain reaction – restriction fragment length polymorphism (PCR-RFLP) of SSU rDNA, rpoD, and gyrB genes. Genomic similarities were confirmed by DNA/DNA hybridization. Only one strain out of 14, TNNIII7, was found to be closely related to the pathogenic bacteria. Neither the phenotypic nor the genotypic markers used in this study were able to distinguish pathogenic from non-pathogenic strains of the widespread V. splendidus. However, future genetic comparisons of TNEMF6 and TNNIII7 is likely to reveal genes involved in pathogenicity.  相似文献   

19.
北部湾钦州港近江牡蛎重金属污染分析   总被引：2，自引：0，他引：2  
为近江牡蛎的食用安全及养殖环境监督管理提供科学依据,2015年7—11月在北部湾钦州港采集近江牡蛎样品,利用原子荧光光度计和原子吸收光谱仪测定近江牡蛎体内重金属含量,分析其污染程度。结果显示,调查海域牡蛎体内重金属平均含量从高到低依次为ZnCuCdCrAsPbHg,其中Zn、Cu含量较高,平均值分别为532.03、126.96 mg/kg。Cu参照《无公害食品水产品有毒有害物质限量》(NY 5073-2006),发现除了7月2号站样品未超标,其余样品均超标,超标率达89%。As参照《食品安全国家标准食品中污染物限量》(GB 2762-2012),发现总超标率为11%,仅7月3号站样品存在超标。Pb、Hg含量较低,其平均值分别为0.02、0.009 mg/kg。重金属富集系数揭示近江牡蛎对Zn、Cu、Cd、Cr富集严重。膳食暴露评估方法显示,重金属的膳食摄入量低于联合国粮食和农业组织的食品添加剂联合专家委员会(JECFA)推荐的暂定每周摄入量,钦州湾近江牡蛎属于安全食用范围。  相似文献   

20.
The growth and survival of Crassostrea gigas were evaluated in hanging culture in the Chone River estuary (Bahía de Caráquez), Manabí province, Ecuador. Oyster seeds (~10 mm) were confined in lantern nets at a density equal to the occupation of half the surface of the basket base, until reaching commercial size (80 mm). A sample for oyster biometric, parasitic and bacterial analysis was obtained monthly. Temperature, salinity, oxygen concentration, seston and phytoplankton biomass were determined. At the end of the study, the oysters were analysed for heavy metal concentration. The commercial oyster production was extrapolated to estimate the possible economic performance of a family production module (a 7 × 7 m bamboo raft). The results show a great biological feasibility of culture of C. gigas with harvests of commercial size oysters in only 5 months and acceptable survivals (accumulated >70%, after 3 weeks of crop seed selection). The heavy metal concentrations and the parasitological and bacteriological analyses did not indicate levels of contamination. The economic projections suggest that, even with a profitability of 57%, the initially invested capital could be recovered within the first harvest.  相似文献   

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