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1.
The freshwater pearl mussel (Margaritifera margaritifera) is a highly specialized and sensitive freshwater bivalve, whose survival in the juvenile phase is indicative of high quality habitats. This contribution investigates the use of juvenile freshwater pearl mussels as bioindicators, considering the influence of mussel stock and study stream conditions on juvenile performance, as described by survival and growth rates. A standardized cross experiment was carried out investigating juvenile performance in four different pearl mussel stocks originating from the Rhine, Danube and Elbe drainages, representing distinct genetic conservation units. The juveniles were exposed in five study streams which were selected to integrate pearl mussel streams with different water qualities and recruitment status of the mussel population. Per study stream, five standard mesh cages containing an equal number of 20 (10 × 2) juvenile pearl mussels per stock in separate chambers were installed. Survival and growth rates of juveniles were checked after three months (i.e. before their first winter) and after nine months (i.e. after their first winter). Mussel stock and study stream conditions significantly influenced juvenile performance. Growth rates were determined by study stream conditions and increased with stream water temperature, organic carbon and C/N ratios. Survival rates varied stock-specifically, indicating different levels of local adaptation to their native streams. Due to the detection of stream-specific differences in juvenile performance, freshwater pearl mussels appear suitable as bioindicators. However, a careful consideration of stock-specificity is necessary to avoid false interpretation of bioindication results. The comparison of stock-specific survival in native versus non-native streams implicates that exposure of juveniles outside their native habitats is able to increase breeding success or else serve for risk spreading in breeding programs.  相似文献   

2.
The freshwater pearl mussel Margaritifera margaritifera (L., 1758) is considered to be a critically endangered species. It is important to obtain information on the distribution and status of the surviving populations of the species, but in Russia this work is still problematic due to the size of the country’s territory, combined with the insufficient number of available specialists. “Searching rules” have been proposed to remotely identify potential pearl mussel habitats in rivers. The most important criteria are relating to the lakes found at the rivers’ sources, as well as to the extent of the deforestation along river basins. About 200 watercourses of the Russian section of the Baltic Sea basin were evaluated using these “rules”. As a result, two previously unknown, viable populations were discovered (comprising about 53,000 specimens), while the absence of pearl mussels was made evident among some rivers which were traditionally believed to be their habitats. The obtained data provides an update on the status of pearl mussels in Russian territories located south of the 61 st degree of latitude. There are 10 populations of this species; 4 of them are almost extinct, 6 are relatively numerous but declining. The total number of pearl mussels hardly exceeds 90,000 individuals.  相似文献   

3.
The freshwater pearl mussel was historically abundant in many streams and rivers in the Elbe, Oder, and Danube Basins in the Czech Republic, Central Europe. By the 21st century, the mussels had become extinct in the lower and middle altitudes, and current populations are only present near the upper limit of their natural range. The current population of this mussel is estimated to be only 1% of the historical abundance. The population decline was related to the negative impacts of pollution from industry, intense agriculture, forestry, and sewage water. The freshwater pearl mussel habitat has also been impacted by watercourse regulations and has been fragmented by dams and weirs. All of these impacts have resulted in failure of the reproductive cycle; the last significant cohort of juveniles settled approximately 30 – 40 years ago. Therefore, this species is considered critically endangered, and an action plan was developed to conserve the populations in the Czech Republic. Special measures were conducted between 1984 and 2005 to improve the age structure of elderly populations. Fish infected with millions of glochidia were released in two locations, and over 53,000 captive-bred juveniles that were three to five years old were released in seven locations. Only the latter approach resulted in a small number of subadults that gradually emerged from the substratum to the bottom surface, as confirmed by monitoring efforts. Despite simultaneous efforts to restore mussel habitat over the last 25 years, natural reproduction still does not occur in the Czech Republic. Therefore, complete restoration of oligotrophic streams is the key to the future presence and natural reproduction of freshwater pearl mussels in the Czech Republic.  相似文献   

4.
Unionoid mussels are obligate parasites on one or more fish species. The objective was to compare growth and survival of encysted mussel larvae of the freshwater pearl mussel (Margaritifera margaritifera) on young-of-the-year (YOY) versus one-year old brown trout (Salmo trutta). YOY and one-year old trout from the Brattefors and Lärje Rivers, Sweden, were infested with mussel larvae from their home river. The mass-normalized encystment abundance was higher on YOY trout than on one-year old trout. The proportional decrease in mass-normalized encystment abundance was larger on YOY brown trout from the Brattefors River than on YOY brown trout from the Lärje River. Encystment per individual fish was higher on YOY trout than on one-year old trout from the Brattefors River, whereas this relationship was reversed for trout from the Lärje River. Larval growth was higher on YOY trout than on one-year old trout. There was a larger difference in larval growth between YOY trout and one-year old trout from the Brattefors River than on the brown trout from the Lärje River. The ability to use both YOY and older fish, such as in the Lärje River, may increase the reproduction potential of mussel populations, compared to a reduced ability to use more than one year class, such as in the Brattefors River. This may also affect the dispersal of mussels, as older brown trout often move and migrate to a higher degree within and between rivers. The dispersal potential of mussels may therefore be relatively high in the Lärje River, but low in the Brattefors River. In rivers where the mussels have to rely on YOY brown trout, it could be worth facilitating passage through migration obstacles for YOY brown trout. Infested YOY brown trout could be artificially re-distributed within rivers, to places with former mussel distributions. It could also be worth testing the suitability of brown trout of different age classes when starting breeding programs.  相似文献   

5.
Substrate conditions are considered crucial for the survival of juvenile freshwater pearl mussels (Margaritifera margaritifera L.) – and therefore for the recovery of overaged populations in danger of extinction – as fine sediments can clog the interstitial habitat and hamper water and oxygen circulation to the juveniles. Watercourses and their bed sediments must meet two seemingly diametrically opposite requirements in order to offer the freshwater pearl mussel appropriate habitats: stable substrates for all live stages and an unclogged interstitial for the juveniles. As only few scientific publications deal with subsurface conditions in pearl mussel brooks, the present preliminary study tries to contribute to this topic by compiling a variety of chemical and hydromorphological data from several Austrian watercourses with distinctly different characteristics. It was clearly shown that discharge patterns, hydraulic pressure, water depths and flow velocities affect both river bed stability and the perfusion of the hyporheic zone: In an artificial millrace with permanent low flow conditions and a permanently stable substrate a distinct barrier was detected within the first 5 cm substrate depth that totally blocks the interchange between surface and interstitial water, resulting in an accumulation of substances of all kinds, among them potentially toxic substances. Such a barrier was also found to be building up in several natural watercourses, clearly indicating the danger of adverse land-use and of long-term low flow conditions in smaller brooks (given that the local decrease in precipitation, proven in long-term studies, proceeds). Significant differences in substrate concentrations in the interstitial water were detected between watercourses, whereas chemical conditions in the surface water exhibited no differences at all. An accompanying biomonitoring study showed high survival rates all over the study area, indicating the suitability of juvenile freshwater pearl mussels as bioindicators in terms of surface water, but not of interstitial water.  相似文献   

6.
The freshwater pearl mussel (Margaritifera margaritifera) is declining throughout its entire range. On the river Rede, North-East England, the population has been equally declining and shows no apparent recruitment. The study presented here aimed at characterizing water quality and habitat conditions for pearl mussels to identify possible indicators of pressures on the population and inform a restoration and conservation strategy. Water quality monitoring revealed levels of turbidity and suspended sediments to be above the limit set for functional pearl mussel rivers. Substrate sampling revealed silt was present at all sites. A loss of redox potential between the water column and the substrate occurred at all sites, indicating non suitable conditions for juvenile pearl mussels. These investigations suggest that fine sediment input in the river could be one of the factors preventing the development and survival of juvenile mussels while adults face water quality largely affected by high turbidity and high phosphate load. Restoration strategy for the Rede pearl mussel population should focus mainly on limiting sediment and nutrient input in the river throughout the catchment in order to improve habitat for juvenile pearl mussels. This work highlights the need for a catchment-based approach in order to succeed in the conservation of a fragile species.  相似文献   

7.
The Ballinderry River, Co. Tyrone (SAC), is one of only six rivers in Northern Ireland that still supports a population of the globally endangered freshwater pearl mussel, Margaritifera margaritifera. Fewer than 1000 individuals still exist in the river; without intervention it is predicted the Ballinderry pearl mussel will be extinct by 2098. This paper aims to identify key catchment pressures on remaining mussel stocks and prioritise tributaries within the catchment for remediation work to ensure effective targeting of limited resources. A combination of redox assessment, river surveys and SCIMAP modelling was used to rank tributaries, taking into consideration their size and proximity to the main mussel population at the “sanctuary site”. Diffuse and point sources of sediment were identified within the prioritised catchment. The Tulnacross tributary was selected as the highest priority tributary and has been used in a pilot remediation study. A number of different hard and soft engineering techniques have been used for remediation as well as replacing cattle drinkers with pasture pumps and fencing alongside the river. Initial observations suggest river substrate is cleaner. This study is an example of how to tackle problems within a large-scale catchment with limited resources with participation of local stakeholders and riparian landowners.  相似文献   

8.
Bivalve molluscs are newly discovered models of successful ageing. Here, we test the hypothesis that extreme longevity of freshwater mussels is associated with an enhanced resistance to oxidative stress. We assess whether resistance to oxidative stress might be causally involved in the exceptional longevity exhibited by the freshwater pearl mussel Margaritifera margaritifera. We compared resistance to oxidative stress and total haemocyte counts, a health status biomarker in M. margaritifera (maximum lifespan potential 190 years) with three other freshwater bivalve species spanning a range of longevities. Previous studies of the comparative stress resistance and longevity of marine bivalves provide evidence for the hypothesis that an association exists between longevity and not only an enhanced resistance to oxidative stress but also a general resistance to multiplex stressors. We compared baseline total haemocyte counts, age-related changes, and responses to exposure to the oxidative stressor tert-butyl hydroperoxide (TBHP). Surprisingly our data does not support the premise that extreme longevity in M. margaritifera is associated with enhanced resistance to oxidative stress. In comparison with its shorter-lived counter parts M. margaritifera was the least resistance to oxidative stress. Following TBHP exposure, no association between longevity and resistance to oxidative stress-induced mortality nor a marked resistance to oxidative stress-induced declines in total haemocyte counts were observed. The results suggest longevity evolved separately in freshwater mussels and this group warrants further attention from biogerontologists because such study may provide novel insights not detected through the study of the marine members of the class, where most attention is currently focused.  相似文献   

9.
Many of the unionoid mussel species are threatened, and to be able to develop strategies for effective conservation, one of the needs is to distinguish host fish species from non-host fish species using reliable methods. Margaritifera margaritifera lives as a parasite on brown trout (Salmo trutta) and/or Atlantic salmon (Salmo salar). The aim was to compare the reliability of two methods measuring the host specificity of M. margaritifera in two rivers that flow out into Skagerrak in the Atlantic Ocean. A second aim was to compare the time- and cost-efficiency of the two methods. The methods were (1) natural encystment abundances on fish in their native streams using electrofishing, and (2) encystment abundances from controlled artificial infestation in aquaria, on fish that were sacrificed. In both rivers, young-of-the-year (YOY), but not older brown trout, were naturally infested with relatively low loads of glochidia larvae, while the Atlantic salmon was not infested at all. When using artificial infestation, both YOY and older brown had encysted glochidia larvae on their gills, while glochidia larvae were not able to develop in Atlantic salmon at all. Here, the encystment was higher on the brown trout from the Lärje River, and older brown trout from the Lärje River did not seem to have as strong immunity response compared to older brown trout from the Brattefors River. In summary, brown trout is the only host fish for M. margaritifera in these rivers. Both methods can be used to discriminate between host fish species, but the method measuring natural encystment seems most time- and cost-efficient. In addition, natural encystment can be measured using a non-destructive photo-method, and is therefore suggested to be used when discriminating between host fish species for M. margaritifera.  相似文献   

10.
Oxygenated streambeds are considered a key requirement for the successful recruitment of stream fauna, including highly endangered freshwater pearl mussel Margaritifera margaritifera. Excessive amounts of fines impede exchange between open water and interstitial, leading to colmation and low oxygen levels in the juvenile habitat. Understanding the dynamic relationship between sediment delivery, transport, deposition and remobilization in relation to anthropogenic drivers is still poorly understood, yet is essential for conservation and restoration.This study analysed spatiotemporal sediment dynamics and interstitial habitat quality in five pearl mussel streams at the border region between Bavaria, Saxony and the Czech Republic during 2018 and 2019, comparing extremely dry periods with higher discharge events caused by snow melt and rainfall. Physicochemical habitat conditions within the streambed and sediment deposition were recorded in high spatial resolution along the stream courses, with a particular focus on the effects of tributaries and outflows of man-made fishponds.Habitat conditions were unsuitable for juvenile pearl mussels at the majority of sites, indicated by pronounced differences in physicochemical parameters between open water and the substrate, independent of discharge conditions. Sediment deposition varied markedly between discharge events, in terms of both the quality and quantity of deposits. Snow melt resulted in the highest sedimentation rates, but the smallest proportion of fine particles. During low flow conditions, fine sediment deposition was highly variable, ranging from 0.048 to 4.170 kg/week/m², mostly independent of flow velocity. High spatiotemporal variation was observed within and amongst stream systems, revealing different longitudinal patterns of fine sediment deposition, with catchment land use as the main driver. Temporal variability in sediment deposition was mainly associated with the discharge condition while abiotic parameters varied mainly with season.The high site-specificity of sedimentation rates and substrate conditions in response to different discharge events highlights the importance of an adapted conservation management which considers anthropogenic effects at the local scale.  相似文献   

11.
Changes in the vegetation cover associated with intensive forest extermination may have a strong effect on the riverine environment, including the chances of survival for bivalve mollusc populations in small streams and rivers. In order to check this hypothesis, drainage area properties of the rivers with extinct and existing pearl mussel populations in the Russian section of the Baltic Sea basin were compared. Preservation of forest vegetation along the river banks of the studied rivers was correlated with the presence of pearl mussel populations. Traditional agriculture turned out to be, in some cases, more harmful for river ecosystems than urbanization and industrialization.  相似文献   

12.
Fine sediment deposition in stream beds frequently generated by certain land use practices has become an increasing stressor for rivers throughout the world. In this study, the role of fine sediment deposition and its impact on the benthic macro-invertebrate assemblages was investigated in a low mountain freshwater pearl mussel stream, the Waldaist. Communities of unaffected sites and sites under high fine sediment deposition were compared. Distinct reactions of benthic assemblages in fine gravelly habitats were ascertained demonstrating a severe but still underestimated threat for invertebrate biodiversity.  相似文献   

13.
淡水蚌类是全球最受威胁的动物群之一.加强淡水蚌类灭绝机制的研究,对促进野生淡水蚌类生物多样性的保护和管理具有重要的意义.淡水蚌类具有独特的生活史,发育过程中的钩介幼虫必须依赖于宿主鱼才能完成变态发育.淡水蚌局部种群之间的交流是通过宿主鱼的迁移和幼虫漂流来实现的.通过对鄱阳湖12个采样地点调查,计算了39种淡水蚌的局部定居率和灭绝率,利用一般线性模型,通过比较最低赤池信息准则和许瓦兹贝叶斯准则来评估淡水蚌类的8个生物学特征对预测种群局部定居率和灭绝率的可行性.结果表明:淡水蚌类的生物学特征与局部定居率和灭绝率存在相关性,可以用来预测种群局部定居和灭绝,其中种群结构和繁殖时期这两个生物学特征是预测局部定居率的最佳组合模型,分布密度、繁殖能力、保护现状和运动能力是预测局部灭绝率的最佳结合模型.就鄱阳湖淡水蚌类而言,局部灭绝率显著超过局部定居率,表明局部种群隔离程度正在加重,面临着严重的种群灭绝危机.  相似文献   

14.
Amik Lake or, historically, Lake of Antioch, was a large freshwater body in the lower Orontes River basin (Hatay Province, Turkey) that was drained in the 1940s–1970s. Several endemic animal species were described from this lake, including the freshwater mussel Anodonta pseudodopsis Locard, 1883 (Bivalvia: Unionidae) characterized by a large rounded shell covered by a peculiar yellow or yellowish-brown periostracum. Molecular analyses of topotypes of this nominal taxon collected from the former lake’s tributaries in the Amik Plain indicate that it is an intra-specific lineage of the widespread Anodonta anatina (Linnaeus, 1758) based on the mitochondrial COI and 16S rRNA, and the nuclear 28S rRNA gene fragments. Geometric morphometric analyses using the lectotype and topotypes of Anodonta pseudodopsis support our DNA-based hypothesis on the status of this nominal taxon. A new synonymy is provided as follows: Anodonta anatina = Anodonta pseudodopsis syn. nov. The syntype of Anodonta pseudodopsis SMF 5129 “See von Antiochia” (Senckenberg Research Institute and Natural History Museum, Frankfurt, Germany) is designated here to be the lectotype of this nominal taxon. Finally, we conclude that Anodonta anatina range covers the Orontes River basin in Turkey and Syria and the Nahr al-Kabir al-Shamali River in the Latakia Governorate of Syria. This intraspecific lineage of Anodonta anatina and other freshwater mussels of the Middle East are highly threatened due to multiple anthropogenic impacts and must be a focus of international conservation efforts. The Karasu River in eastern Turkey hosts viable populations of all freshwater mussel species of the Orontes’s fauna and can be considered one of the most important water bodies for the conservation of these imperiled animals in the region.  相似文献   

15.
《Marine pollution bulletin》2013,66(10-12):453-462
Bivalve larvae and hydrographic parameters were sampled over a range of spatio-temporal scales in a deep atoll lagoon. Bivalve larvae abundances were very high throughout the year: 18,550 m−3 in average. Larvae were (i) concentrated at mid-depth with nocturnal ascent and diurnal descent, (ii) heterogeneously dispersed at the lagoon scale, (iii) subject to day-to-day variation in abundance and (iv) transferred between different parts of the lagoon providing evidence of intra-lagoonal connectivity. The primacy of physical factors was seen on large spatial scale with the diluting effect of water renewal and transfers by hydrodynamics. On smaller spatial scale, the primacy of biological processes was recognised, with larval swimming activity leading to dial vertical migration correlated with food concentration. Variations in larval abundance were driven by bivalve reproductive activity correlated with meteorological conditions (i.e. windy periods). Finally, relationship between bivalve larvae patterns and pearl oyster (Pinctada margaritifera) settlement structuring is discussed.  相似文献   

16.
Sixty female flounder (Platichthys flesus) were collected in Autumn 2011, 15 from each of the following sampling sites: at the mouths of the Douro and Vistula Rivers, and at nearby open sea locations. The aim of the study was to assess several biomarkers in the two geographically distant regions. Hepatic EROD, GST, SOD, GPx, POx, LP; muscular AChE, BChE, LP; and branchial Na+/K+-ATPase were analysed. Moreover, BTI, PY, and three gross morphometric indices were calculated. The results were analysed with t-test, ANOVA, and PCA. Many differences were found between the open sea sites and the river mouths, mainly in Portugal, and between the two rivers. Salinity and pollution seem to be the main factors that affected the biomarkers. Effects of chronic pollution were observed at the river mouths, and an indication of a possible temporary exposure to pollutants was found at the open ocean site in Portugal.  相似文献   

17.
Erosion and sediment yield are a significant problem in the Guadalquivir River basin. Such phenomena are largely driven by a land use devoted to intensive cultivation of olive trees, with a large socioeconomic influence in Andalusia. This sediment overload in rivers causes serious impacts on all fluvial ecosystem components.In this study we assess the chronic effect of sediment yield on fish communities at 104 river sites located in two different sub-catchments – the Bembézar and Guadajoz rivers – both with different lithological composition and erosion rates. Sediment yield was estimated using a semi-quantitative Factorial Score Model (FSM), developed specifically for Spanish rivers. The fish populations of both basins were evaluated in composition and abundances by the study of Fernández-Delgado et al., 2014. The influence of sediment yield on the fish community was analyzed using General Additive Models.The sediment yield was higher in the Guadajoz basin (921 T/Km2 per year) than in Bembézar (701 T/Km2 per year). In the former, fish communities were poorer in both fish density and diversity, with Luciobarbus sclateri as the only substantially present species and a significant relationship between sediment yield and load, and fish density. In contrast, in the Bembézar basin, sediment yield was correlated with total fish density, including Luciobarbus sclateri, Pseudochondrostoma willkommii, Cobitis paludica, Iberochondrostoma lemmingii, Anaecypris hispanica, and Cyprinus carpio. Intermediate values of sediment yield led to maximum densities, while those higher decreased the density of these species.  相似文献   

18.
The clade of the Iranian freshwater Aphanius species from endorheic and exorheic drainage basins contains three subclades, of which the Aphanius sophiae subclade with seven species is the most specious one. Recently, two previously not known populations of Aphanius were discovered in two isolated basins; one in the Arjan Wetland (Helleh subbasin), and the other in the Semirom spring (Karun Basin), both are located in the Central Zagros Mountains (SW Iran). The objective of this study is to investigate their taxonomic status, to elucidate their phylogenetic relationships and to contribute to future conservation strategies and habitat management of the freshwater species of Aphanius in Iran. Methods include analysis of genetic data based on mtDNA (cyt b), combined with meristics, morphometrics, scale sizes (J-indices) and otolith data. The results based on cyt b clearly indicate that two species are present in the Arjan Wetland, one is closely related to A. sophiae (currently thought to be restricted to the Kor Basin), the other represents Aphanius shirini (previously only known from its type locality Paselari spring). However, significant phenotypic differences are not present between these two species. The second population from the Semirom spring is sister to A. sophiae (Kor Basin) according to cyt b data, but differs significantly from this species with regard to the phenotype. The presence of A. shirini in the Arjan Wetland is most likely be explained by man-made introduction because of the recent droughts. The similarity of the two species present in the Arjan Wetland may be due to phenotypic plasticity, but also hybridization could have played a role. The isolation of populations of A. sophiae is discussed in the context of the active geological history and climate change, and it is likely that their divergence happened in the Early or Middle Holocene (c. 11,700–4000 y. ago). The presence of A. sophiae in the Helleh subbasin and Karun Basin extends the currently known zoogeographic range of this species, which previously has only been reported from the Kor Basin. Such knowledge is important for future conservation strategies and habitat management.  相似文献   

19.
Many cultured pearl farms are located in areas of the Pacific that have thriving, highly diverse fish communities but the impacts of farming on these communities are poorly understood. We studied the effects of pearl oyster farming on shore fish abundance and diversity in the lagoon of Ahe, French Polynesia by adapting roving diver census methods to the coral reef bommies of the lagoon and compared 16 sites with high pearl farming impact to others with no direct impact. Pearl farming has a slightly positive effect on reef fish abundance (N) and no significant impact on fish diversity (H) or community composition. This is important when considering the ecological sustainability of pearl farming in French Polynesia and suggests that a potential synergy between pearl farms and marine conservation should be further explored.  相似文献   

20.
The ecological state of 18 small rivers in Minsk Region was for the first time estimated by jointly used macrophyte-based characteristics, including saprobity index, biological macrophyte index for rivers, and a scale of cenotic/supercenotic organization of aquatic and coastal-aquatic plants. Rivers with relatively safe ecological status were shown to dominate, while other rivers are in a safe and satisfactory state. The proposed approach to determining the ecological quality of watercourses is based on the calculation of a complex characteristic, i.e., an integral macrophyte index of small river ecological status; this index has been developed in the context of a classification scheme of surface water quality in the National Environmental Monitoring System of the Republic of Belarus.  相似文献   

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