三角帆蚌瘟病的防治

我省珍珠业的发展始于六十年代末。育珠蚌有三角帆蚌、褶纹冠蚌、背角无齿蚌等，其中尤以三角帆蚌以育成的珍珠质量最佳，价值最高。但自七十年代中期，江南一带出现大面积三角帆蚌死亡现象。当初，我省有些地区从外省购进不少三角帆蚌，导致我省1983年发生三角帆蚌暴发性的死亡，一直延续至今，群众称之为三角帆蚌瘟病，     

三角帆蚌疾病的初步研究(简报)

<正> 三角帆蚌(Hyriopsis cumingii)是当前淡水蚌珠生产中最佳的蚌种,一直为育珠者广泛采用。但是,自1975年以来,多数育珠地区,经插珠和未插珠的三角帆蚌均常因发病而导致大批死亡,造成重大损失。生产单位被迫改用褶纹冠蚌(Cristaria plicata)育珠,但珍珠质量不如三角帆蚌的好。因此,防治流行广,危害大的三角帆蚌病的问题,已成为亟待解决的问题。     

三角帆蚌蚌瘟病的防治技术

三角帆蚌蚌瘟病的防治技术潘炳炎，文仲芬（淡水渔业研究中心无锡２１４０８１）三角帆蚌是我国淡水人工育珠中的优良品种，所产珍珠具有光泽好、珠粒圆的特点，但作为育珠用的三角帆蚌，在生产过程中因病害而大批死亡，给育珠生产造成重大损失，特别是三角帆蚌的蚌瘟病，...     

提高三角帆蚌幼蚌成活率和珠质的试验

1979年以来，我县三角帆蚌蚌病蔓延严重，育珠蚌的成活率甚低，严重的地方甚至全部死亡。据统计，1979年以前，全县养殖的三角帆蚌要占总数的80％左右，三级以上的优质珠占21．6％。尔后，随着蚌病的蔓延，三角帆蚌的比例下降到10～20％(1981)，三级以上的优质珠下降到3．2％；当年繁殖的三角帆蚌幼蚌也只长到3～4厘米，到第三年后才能达到10厘米左右，方能作育珠蚌用，接种后三年才能收珠，整个周期共需六年时间。     

三角帆蚌瘟病的病原鉴定

三角帆蚌近几年连续发生大面积死亡,群众称之谓三角帆蚌瘟病。对49个疫点的调查与实验观察表明,不同地区的三角帆蚌大批死亡具有相同的基本特征:本病发生在夏秋两季,只侵害2令以上的三角帆蚌,当年死亡率可达80％左右。本病病程较长,并与环境温度呈密切的负相关:y=52.8653-1.5830x,γ=-0.7693,P<0.01。发病蚌的排水与进水孔纤毛收缩,排粪减少,晚期无粪,张壳死亡。野外与实验室内均能自然感染健康帆蚌。氯霉素、四环素等多种药物在野外与实验室治疗均无效果。自然发病蚌以及相应除菌材料人工感染的发病蚌,病变部位与病变性质相互一致:消化腺与多种上皮细胞水泡变性,消化腺细胞浆出现缎密的酸性包含物,内质网普遍地高度扩张,这符合于一般动物病毒病的组织病理特征。     

三角帆蚌的人工繁殖及幼蚌的培育

三角帆蚌排放钩介幼虫(以下简称排卵)的水温为15～30℃范围内，以18—25℃为排卵盛期。从时间上说，4月中旬即有少量三角帆蚌达到性成熟。5月下旬到6月中旬．三角帆蚌大批达到性成熟。直到8月，仍有性成熟母蚌继续排卵。在环境条件较好、母蚌体质健壮的情况下，三角帆蚌可以在一年中数次排卵，一般可排放3—4次，少数可排卵7—8次之多．     

不同来源的嗜水气单胞菌（Aeromonas hydrophila）对三角帆蚌的致病性研究

探讨了４种不同来源的嗜水气单胞菌对三角帆蚌的致病力。４种来源的嗜水气单胞菌菌种经复壮、分离、鉴定、人工感染健康三角帆蚌均能引起其发病死亡,临床发病症状相似,但对三角帆蚌的毒力有差异,以甲鱼嗜水气单胞菌对三角帆蚌的毒力最强,牛蛙嗜水气单胞菌的毒力最弱。     

三角帆蚌耗氧率和窒息点的初步研究

本文重点报道三角帆蚌的成年蚌(即育珠蚌)的群体耗氧率和窒息点的测定结果。三角帆蚌在水温19℃左右时,24小时平均耗氧率为8.5341毫克/千克/小时,褶纹冠蚌为17.4908毫克/千克/小时。三角帆蚌的窒息点是0.1～0毫克(O_2)/升状态下,168小时才死亡。     

在太湖首次人工放养三角帆蚌幼蚌

近年来，随着珍珠养殖事业的发展，三角帆蚌成蚌已供不应求，太湖中的三角帆蚌资源也因被大量“扒取”日趋衰竭。为了使太湖中三角帆蚌的资源得以恢复，该湖渔管会于今春首次在湖中投放了三角帆蚌幼蚌。     

三角帆蚌的瘟病防治

三角帆蚌的瘟病防治潘炳炎，文仲芳（中国水产科学研究院淡水渔业研究中心，无锡２１４０８１）三角帆蚌瘟病是由嗜水气单胞菌、嵌砂样病毒所引起，常在夏秋两季蔓延。江、浙一带每年５～６月和９～１０月（水温２１～２６℃）为蚌瘟病流行季节，来势凶猛，死亡率甚高。一...     

Prediction of potential freshwater pearl mussel habitat aids in discovery of a large population of Margaritifera laevis in Iturup Island,Russia

1. Freshwater pearl mussels (family Margaritiferidae) are sensitive to human impact and environmental changes. Large declines in their abundance have prompted studies of distribution and estimations of population densities.
2. Iturup Island, a part of Kuril Islands, Russia, is considered to be within the distribution area of freshwater pearl mussels, but this information is based on only two specimens collected several decades ago. Detailed survey of the island is challenging as most of its territory is nearly impassable.
3. A preliminary analysis of island rivers was carried out prior to the surveys to discover potential freshwater pearl mussel habitats. Based on previous experience from European Russia, freshwater pearl mussel habitat was expected to occur in rivers flowing out of lowland lakes.
4. Live individuals of Margaritifera laevis were found during surveys in one river together with the unionid Beringiana beringiana, which were also found in two other rivers where the predicted habitat occurred. Based on prediction and surveys, the occurrence of freshwater pearl mussels in other rivers of Iturup Island is unlikely.
5. Pearl mussels were concentrated in a small section of the Zmeika River with a population of about 100,000 mussels. Present threats to the population include overharvest of host fish masou salmon (Oncorhynchus masou).
6. Surveys using similar methods can help to reveal unknown freshwater mussel populations on other Kuril Islands and on the mainland.

     

Freshwater mussel abundance predicts biodiversity in UK lowland rivers

• 1. Indicator taxa are widely used as a valuable tool in the assessment of freshwater biodiversity. However, this approach to identifying sites of conservation priority requires surveyors to possess expert taxonomic knowledge. Furthermore, sorting and microscopic examination of material can present logistical and financial constraints.
• 2. Comparisons were made between the taxon richness and the density of freshwater mussels (Bivalvia: Unionidae) from 30 sites in seven UK lowland rivers, ranging from ca 3 m to 50 m width and ca 0.5 m to 4 m depth. Where mussels occurred, taxon richness of other invertebrates was strongly correlated with both mussel density and mussel biomass. Overall mussel density was a better predictor of taxon richness than the density of any individual mussel species.
• 3. It is suggested that this association arises from the ‘keystone’ role that mussels play in many freshwater ecosystems. Local biota can benefit from the mussels' filtration, excretion, biodeposition and physical presence.
• 4. Using mussel abundance as a surrogate provides a rapid and straightforward alternative to conventional methods of assessing freshwater biodiversity. No expert knowledge is required and any standardized sampling technique can be used. Freshwater mussels are found throughout the world's lentic and lotic fresh waters and this approach therefore has the potential for widespread utility, especially where rapid comparisons of biodiversity are required between biogeographically similar regions. In addition, the results highlight the ecosystem‐level consequences of allowing the global decline of freshwater mussels to remain unchecked.

Copyright © 2007 John Wiley & Sons, Ltd.     

A critical reflection on the success of rearing and culturing juvenile freshwater mussels with a focus on the endangered freshwater pearl mussel (Margaritifera margaritifera L.)

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Estimation of gut contents of freshwater mussel, Lamellidens marginalis L.

This study examined the food organisms found in the gut of freshwater mussels, Lamellidens marginalis L. A total of 34 taxa of food organisms were recorded, out of which 30 taxa belonged to phytoplankton and four taxa to zooplankton. Both the groups comprised three families each: Cyanophyceae (blue‐green algae), Chlorophycea (green algae) and Bacillariophyceae (diatoms) constituted phytoplankton, whereas Euglenaceae, Chlamydodontidae and Brachionidae belonged to zooplankton. The total number of frequencies of phytoplankton (n=537) were almost nine times more than that of zooplankton (n=60). When blue‐green algae, green algae, diatoms and zooplankton (all the three families together) were tested for significant difference (P<0.05) following Duncan's multiple range test, the result showed only two groups. Blue‐green algae, green algae and zooplankton were not significantly different (P<0.05), forming group A, whereas diatoms were significantly different from others, forming group B. The present study showed that the maximum number of organisms that mussels feed upon belong to green algae, followed by diatoms, blue‐green algae and few taxa of zooplankton.     

Development of release methods for captive‐bred freshwater pearl mussels (Margaritifera margaritifera

1. Biodiversity loss is a global problem with freshwater bivalves considered among the most endangered biota. The freshwater pearl mussel, Margaritifera margaritifera, is declining throughout its range owing to habitat degradation and overexploitation. In most of its range, populations are regarded as reproductively non‐functional, which has led to the development of captive breeding programmes.
2. A novel method of releasing M. margaritifera was tested, with captive‐bred juveniles being released into the rivers caged in ‘mussel silos’ (protective concrete domes with ventilation creating upwelling to ensure water through‐flow).
3. In total, 240 juvenile mussels were released and survival and growth rates were monitored for 18 months after release for three size classes: A (13.01–20.00 mm); B (10.01–13.00 mm); and C (4.01–10.00 mm).
4. Two experimental treatments were tested: one in which sediment was added to each silo (allowing mussels to orientate and burrow) and one without sediment. Survival by the end of the experiment at month 18 was significantly higher for the largest size class at 97% (although growth was lowest in this cohort), and lowest for the smallest size class, at 61% (although growth was highest in this cohort). Survival and growth were unaffected by the experimental treatment suggesting that adding sediment offered no advantage. Growth was positively correlated both with water temperature and with particle size of suspended solids (both of which were collinear, peaking in summer).
5. There are many ex situ breeding programmes for freshwater pearl mussels throughout Europe and the results of this study suggest that the use of mussel silos may be a useful tool to protect juvenile mussels, allowing them to be released at a relatively early stage of development and minimizing the risk of domestication.

Copyright © 2016 John Wiley & Sons, Ltd.     

Viability of a Freshwater Mussel (Elliptio complanata) as a Biomechanical Filter for Aquaculture Ponds I: Clearance Rate of Chlorophyll-α

The production and livelihood of aquaculture facilities depend on increased growth of species being harvested. Only 15%-25% of nitrogen and phosphorus are retained in farmed fish even when all feed is consumed. In both marine and freshwater aquaculture systems, bivalves have proven to be an inexpensive method for controlling algal growth through suspension feeding. With 25% of the native U.S. freshwater mussel species under federal protection, their use in aquaculture ponds could lead to further propagation and restoration of natural populations. Elliptio complanata is an important species in Delaware rivers and connected estuaries; a recent two-year study by the United States Geological Survey found that 98% of mussels found in the Delaware River were Elliptio complanata. The objective of this study was to calculate the clearance rate of E. complanata in a laboratory study. This would help us determine if mussels can serve as an addition to chemical and mechanical filtration regiments and thrive in an aquaculture setting. Using feeding chambers we investigated the effect of E. complanata on algae grown from an aquaculture pond and on a cultured alga over a four-hour period. Temperature, dissolved oxygen, and pH were monitored, and samples were than analyzed for total chlorophyll-α. The average of both the single cell using Chlorella vulgaris and mixed assemblage treatments chlorophyll-α clearance rate was 0.187 liters per hour per mussel. Prior to this experiment, these mussels were held for a period for two months in the holding system in the laboratory. The resulting low clearance rate as compared to the previous studies in the field is possibly due to the stress from holding these mussels. However, our study demonstrated that mussels have the potential to be used in an aquaculture setting and/or recreational ponds to help reduce algae populations that can occur as a result of eutrophication.     

Status of the endangered Glenelg River Mussel Hyridella glenelgensis (Unionoida: Hyriidae) in Australia

• 1. Hyridella glenelgensis is a small freshwater mussel that occurs in the Glenelg–Wannon river system in south‐western Victoria and is listed as ‘threatened’ under the state Flora and Fauna Guarantee Act 1988. The species has rarely been reported since its discovery in 1898, and there are no records from the late 1920s until 1990, and again in 2000, when small numbers were found in the Crawford River, a Glenelg tributary.
• 2. This investigation established that a population still persists in the lower reaches of the Crawford. The mussels prefer sandy sediment in flowing reaches where there is instream woody debris and overhanging vegetation. In these areas, the main threats are land clearance and stock access to the channel and riparian areas.
• 3. The shell morphology of H. glenelgensis and specimens presumed to be H. narracanensis from Eight Mile Creek, south‐eastern South Australia, is distinct. Similar distinctions are apparent for shells from historical museum collections.
• 4. Mitochondrial DNA analysis of very small samples of mussels from the Crawford River and Eight Mile Creek indicates little genetic divergence, suggesting that these could be ecophenotypic variants of one species, which by priority would be H. glenelgensis. Scanning electron microscopy of glochidia indicates morphology typical of the genus.
• 5. Future investigations could include genetic analyses to confirm the taxonomic identity of the populations described here, surveys to locate new populations and measures to protect known habitats.

Copyright © 2007 John Wiley & Sons, Ltd.     

总氮、总磷和钙离子浓度与育珠蚌生长速度的相关性研究

总氮、总磷与钙浓度均是影响育珠蚌生长的主要因素,通过不同处理,进行养殖比较,就三者对蚌生长的相关性程度进行了研究,结果表明:在现有浓度下得出育珠蚌的增重与总氮的偏相关系数为0.998625;总磷的偏相关系数为0.402719;钙离子浓度的偏相关系数为0.995538。     

Rediscovery of the largest population of the freshwater pearl mussel (Margaritifera margaritifera) in the Leningrad oblast (north‐west Russia)

• 1. An internationally important population of the freshwater pearl mussel (Margaritifera margaritifera) was rediscovered in a small river in north‐west Russia.
• 2. A survey of visible mussels in 2008/2009 indicated an estimated population of 40 000 individuals. This is the largest population currently known in the Leningrad oblast and is comparable with the entire pearl mussel population of some western European countries.
• 3. The average density of visible mussels was 29.6 individuals m^?2 in the middle part of the river. In the four largest mussel beds maximum densities of 1000+ individuals m^?2 were recorded. Such densities are exceptional and have not been reported elsewhere in Europe during the last 100 years.
• 4. Live juvenile mussels were recorded, indicating that that this population is viable, although further investigation is required to establish its status.
• 5. Analysis of the population age structure, based on the measurement of empty shells, showed an age class distribution similar to those reported for other healthy Margaritifera populations.
• 6. Only two live juveniles were found. However, this is likely to be due to the survey being restricted to counts of visible mussels only, and the age structure being based on the analysis of dead shells.
• 7. The population's current status and possible reasons for its survival in this river are discussed. Conservation measures should include the construction of a fish ladder to make fish migration through the culvert possible, removal of a metal screen preventing fish migration from the upper reaches of the river to the lake, reduction of recreation activities, and providing the local children's camp with water treatment facilities. Copyright © 2011 John Wiley & Sons, Ltd.