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Amílcar Teixeira - One of the best experts on this subject based on the ideXlab platform.
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Small hydropower plants as a threat to the endangered pearl mussel margaritifera margaritifera.
The Science of the total environment, 2020Co-Authors: Ronaldo Sousa, Simone Varandas, Amílcar Teixeira, Manuel Lopes-lima, Andre L. Ferreira, Francisco Carvalho, Belinda GallardoAbstract:Abstract Freshwater mussels are undergoing rapid global declines due to habitat loss and fragmentation, among other factors, but little is known about the effects of small hydropower plants. Here we assessed the impact of small hydropower plants on the abundance and size structure of the imperilled pearl mussel margaritifera margaritifera. For this, we sampled 66 sites in three Portuguese rivers (Mente, Rabacal and Tuela) located upstream and downstream of dams and within the reservoirs. Pearl mussels were significantly more abundant upstream than downstream of dams (97.4% more) or within reservoirs (98.5% more). In addition, juveniles were mostly found upstream of dams. The most significant environmental alterations that explained the observed patterns were related to changes in sediment characteristics (accumulation of fine sediments and organic matter in reservoirs) and water chemistry, most notably suspended solids (highest values in reservoirs) and dissolved oxygen (lowest values in reservoirs). Overall, results show that small hydropower plants can deeply affect pearl mussel populations: specimens almost disappeared from the areas within the reservoirs and sites located downstream only retained adults without signs of recent recruitment. Future management measures devoted to the conservation of pearl mussels should take into account the results reported here to avoid the construction of new dams in pearl mussel rivers; improve management of the river flow in downstream areas; and consider the decommissioning of dams in pearl mussel rivers with a particular attention devoted to the re-naturalization of river sections under the influence of the reservoir and downstream areas.
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Effects of an extreme drought on the endangered pearl mussel margaritifera margaritifera: a before/after assessment
Hydrobiologia, 2019Co-Authors: Joana Garrido Nogueira, Amílcar Teixeira, Simone Varandas, Manuel Lopes-lima, Ronaldo SousaAbstract:Droughts can change the distribution and alter the behaviour, phenology and physiology of many species, leading in extreme cases to high mortalities or even extirpation. In this study, a before/after comparison was performed in two Portuguese river basins (Rabaçal and Tuela) to assess the possible effects of an extreme drought on the abundance and size structure of two pearl mussel margaritifera margaritifera populations, a Critically Endangered species in Europe. The hydrological year of 2017 was extremely dry in Portugal and this situation was responsible for a major reduction of the river flow and rapid decrease in the water levels during summer. One year after the drought, a significant reduction in abundance was observed (i.e. 27.6% for the Rabaçal and 38.7% for the Tuela basin populations). However, no differences were detected in the size structure of the two pearl mussel populations. Droughts are predicted to increase in number and intensity and it is crucial to monitor M. margaritifera populations, given the low resistance (and possibly low resilience) of this species to these extreme conditions. Management measures that could help the conservation of pearl mussels are discussed.
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Water mill canals as habitat for margaritifera margaritifera: Stable refuge or an ecological trap?
Ecological Indicators, 2019Co-Authors: Ronaldo Sousa, Simone Varandas, Manuel Lopes-lima, Joana Garrido Nogueira, Amílcar TeixeiraAbstract:Abstract Anthropogenic habitats may serve as a refuge for aquatic species, including freshwater mussels (Bivalvia, Unionida). Evaluating the role of anthropogenic habitats is a fundamental, but still ignored, conservation issue given the pace that humans have been converting natural ecosystems. In this study, possible differences in abundance, size and condition index of the freshwater pearl mussel margaritifera margaritifera colonizing anthropogenic (water mill canals) and natural (Tuela River) habitats were assessed. No differences were found in the abundance of freshwater pearl mussels colonizing both habitats, but individuals present in the water mill canals have a significantly higher condition index and size. Water mill canals seem to provide stable conditions for the settlement, growth and survival of freshwater pearl mussels. However, the occurrence of an exceptional drought during the late summer of 2017 was responsible for an almost 100% mortality in one of the two water mill canals surveyed in this study. Therefore, and during extreme climatic events, these anthropogenic structures may function as an ecological trap for freshwater pearl mussels. This study can be used by managers to promote future actions that enhance freshwater pearl mussel protection and guarantee their survival, including on anthropogenic habitats.
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Conservation status of the freshwater pearl mussel margaritifera margaritifera in Portugal
Limnologica, 2015Co-Authors: Ronaldo Sousa, Ângela Amorim, Elsa Froufe, Simone Varandas, Amílcar Teixeira, Manuel Lopes-limaAbstract:Abstract Based on new information, the current conservation status of the freshwater pearl mussel margaritifera margaritifera (Linnaeus, 1758) in Portugal is revised. Between 2010 and 2013 surveys were conducted in eight different rivers to assess distribution, abundance, size-frequency and preferential habitat of this species. Rivers Neiva, Cavado and Terva presented very low abundances (in the Cavado no specimens were found) and showed acute signs of ageing, calling into question the future survival of these populations. Although abundances were low in Rivers Beca, Paiva and Mente, juveniles were present and populations may improve their conservation status in the future, if appropriate management measures are applied. Rivers Rabacal and Tuela presented the highest abundances of adults and juveniles and these two rivers have the highest potential for the conservation of freshwater pearl mussels in Portugal. However, these two populations have suffered severe declines in several stretches due to the construction of dams in recent years. Given that the Portuguese pearl mussel populations are at the southern range of the species distribution, their conservation should be a priority. This current description of the conservation status of M. margaritifera in Portugal can be used as a reference, and guide future research and management initiatives to better conserve this species.
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Ecological status of a margaritifera margaritifera (Linnaeus, 1758) population at the southern edge of its distribution (River Paiva, Portugal).
Environmental management, 2013Co-Authors: Ronaldo Sousa, Ângela Amorim, Carina Sobral, Elsa Froufe, Simone Varandas, Amílcar Teixeira, Manuel Lopes-limaAbstract:An important population of the critically endangered pearl mussel margaritifera margaritifera (Linnaeus, 1758) was surveyed at the edge of its southern distribution (River Paiva, Portugal). Although an earlier study suggested that this population had a very low number of individuals (
Ronaldo Sousa - One of the best experts on this subject based on the ideXlab platform.
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Small hydropower plants as a threat to the endangered pearl mussel margaritifera margaritifera.
The Science of the total environment, 2020Co-Authors: Ronaldo Sousa, Simone Varandas, Amílcar Teixeira, Manuel Lopes-lima, Andre L. Ferreira, Francisco Carvalho, Belinda GallardoAbstract:Abstract Freshwater mussels are undergoing rapid global declines due to habitat loss and fragmentation, among other factors, but little is known about the effects of small hydropower plants. Here we assessed the impact of small hydropower plants on the abundance and size structure of the imperilled pearl mussel margaritifera margaritifera. For this, we sampled 66 sites in three Portuguese rivers (Mente, Rabacal and Tuela) located upstream and downstream of dams and within the reservoirs. Pearl mussels were significantly more abundant upstream than downstream of dams (97.4% more) or within reservoirs (98.5% more). In addition, juveniles were mostly found upstream of dams. The most significant environmental alterations that explained the observed patterns were related to changes in sediment characteristics (accumulation of fine sediments and organic matter in reservoirs) and water chemistry, most notably suspended solids (highest values in reservoirs) and dissolved oxygen (lowest values in reservoirs). Overall, results show that small hydropower plants can deeply affect pearl mussel populations: specimens almost disappeared from the areas within the reservoirs and sites located downstream only retained adults without signs of recent recruitment. Future management measures devoted to the conservation of pearl mussels should take into account the results reported here to avoid the construction of new dams in pearl mussel rivers; improve management of the river flow in downstream areas; and consider the decommissioning of dams in pearl mussel rivers with a particular attention devoted to the re-naturalization of river sections under the influence of the reservoir and downstream areas.
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Effects of an extreme drought on the endangered pearl mussel margaritifera margaritifera: a before/after assessment
Hydrobiologia, 2019Co-Authors: Joana Garrido Nogueira, Amílcar Teixeira, Simone Varandas, Manuel Lopes-lima, Ronaldo SousaAbstract:Droughts can change the distribution and alter the behaviour, phenology and physiology of many species, leading in extreme cases to high mortalities or even extirpation. In this study, a before/after comparison was performed in two Portuguese river basins (Rabaçal and Tuela) to assess the possible effects of an extreme drought on the abundance and size structure of two pearl mussel margaritifera margaritifera populations, a Critically Endangered species in Europe. The hydrological year of 2017 was extremely dry in Portugal and this situation was responsible for a major reduction of the river flow and rapid decrease in the water levels during summer. One year after the drought, a significant reduction in abundance was observed (i.e. 27.6% for the Rabaçal and 38.7% for the Tuela basin populations). However, no differences were detected in the size structure of the two pearl mussel populations. Droughts are predicted to increase in number and intensity and it is crucial to monitor M. margaritifera populations, given the low resistance (and possibly low resilience) of this species to these extreme conditions. Management measures that could help the conservation of pearl mussels are discussed.
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Water mill canals as habitat for margaritifera margaritifera: Stable refuge or an ecological trap?
Ecological Indicators, 2019Co-Authors: Ronaldo Sousa, Simone Varandas, Manuel Lopes-lima, Joana Garrido Nogueira, Amílcar TeixeiraAbstract:Abstract Anthropogenic habitats may serve as a refuge for aquatic species, including freshwater mussels (Bivalvia, Unionida). Evaluating the role of anthropogenic habitats is a fundamental, but still ignored, conservation issue given the pace that humans have been converting natural ecosystems. In this study, possible differences in abundance, size and condition index of the freshwater pearl mussel margaritifera margaritifera colonizing anthropogenic (water mill canals) and natural (Tuela River) habitats were assessed. No differences were found in the abundance of freshwater pearl mussels colonizing both habitats, but individuals present in the water mill canals have a significantly higher condition index and size. Water mill canals seem to provide stable conditions for the settlement, growth and survival of freshwater pearl mussels. However, the occurrence of an exceptional drought during the late summer of 2017 was responsible for an almost 100% mortality in one of the two water mill canals surveyed in this study. Therefore, and during extreme climatic events, these anthropogenic structures may function as an ecological trap for freshwater pearl mussels. This study can be used by managers to promote future actions that enhance freshwater pearl mussel protection and guarantee their survival, including on anthropogenic habitats.
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Conservation status of the freshwater pearl mussel margaritifera margaritifera in Portugal
Limnologica, 2015Co-Authors: Ronaldo Sousa, Ângela Amorim, Elsa Froufe, Simone Varandas, Amílcar Teixeira, Manuel Lopes-limaAbstract:Abstract Based on new information, the current conservation status of the freshwater pearl mussel margaritifera margaritifera (Linnaeus, 1758) in Portugal is revised. Between 2010 and 2013 surveys were conducted in eight different rivers to assess distribution, abundance, size-frequency and preferential habitat of this species. Rivers Neiva, Cavado and Terva presented very low abundances (in the Cavado no specimens were found) and showed acute signs of ageing, calling into question the future survival of these populations. Although abundances were low in Rivers Beca, Paiva and Mente, juveniles were present and populations may improve their conservation status in the future, if appropriate management measures are applied. Rivers Rabacal and Tuela presented the highest abundances of adults and juveniles and these two rivers have the highest potential for the conservation of freshwater pearl mussels in Portugal. However, these two populations have suffered severe declines in several stretches due to the construction of dams in recent years. Given that the Portuguese pearl mussel populations are at the southern range of the species distribution, their conservation should be a priority. This current description of the conservation status of M. margaritifera in Portugal can be used as a reference, and guide future research and management initiatives to better conserve this species.
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Ecological status of a margaritifera margaritifera (Linnaeus, 1758) population at the southern edge of its distribution (River Paiva, Portugal).
Environmental management, 2013Co-Authors: Ronaldo Sousa, Ângela Amorim, Carina Sobral, Elsa Froufe, Simone Varandas, Amílcar Teixeira, Manuel Lopes-limaAbstract:An important population of the critically endangered pearl mussel margaritifera margaritifera (Linnaeus, 1758) was surveyed at the edge of its southern distribution (River Paiva, Portugal). Although an earlier study suggested that this population had a very low number of individuals (
Mark R. Young - One of the best experts on this subject based on the ideXlab platform.
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Characterization of freshwater pearl mussel (margaritifera margaritifera) riverine habitat using River Habitat Survey data
Aquatic Conservation: Marine and Freshwater Ecosystems, 2003Co-Authors: Lee C. Hastie, Mark R. Young, Susan L. Cooksley, F. Scougall, P.j. Boon, Martin J. GaywoodAbstract:1. The feasibility of using River Habitat Survey (RHS) data to describe freshwater pearl mussel (margaritifera margaritifera) macrohabitat in the River Spey, north-east Scotland, was investigated. 2. Mussels were found to be positively associated with a number of RHS variables. These included: boulder/cobble river bed substrates, broken/unbroken standing waves (channel flow types), aquatic liverworts/mosses/lichens and broadleaf/mixed woodland/bankside tree cover. Negative associations with gravel-pebble/silt substrates and emergent reeds/sedges/herbs were also found. 3. Two binary logistic regression models, based on seven and four variables, respectively, were constructed in order to predict the presence/absence of mussels at any given site. Predictive success rates of 83% and 78% were achieved. 4. Another binary logistic regression model, based on four variables, was constructed in order to predict the occurrence of ‘optimal’ M. margaritifera habitat (overall mussel densities ≥ 1 m−2). A predictive success rate of 83% was achieved. 5. The results indicate two potentially important applications of RHS for the conservation management of M. margaritifera: (1) for monitoring the effects of physical changes on extant mussel beds (and predicting their effects on mussel populations), and (2) for determining the habitat suitability of historically occupied sites for re-introductions. Copyright © 2003 John Wiley & Sons, Ltd.
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Freshwater pearl mussel (margaritifera margaritifera) glochidiosis in wild and farmed salmonid stocks in Scotland
Hydrobiologia, 2001Co-Authors: Lee C. Hastie, Mark R. YoungAbstract:Samples of salmonids were taken from six Scottish rivers and examined for freshwater mussel (margaritifera margaritifera (L.)) glochidiosis. The prevalence and magnitude of natural infections observed were comparable to those reported elsewhere. In most rivers, older fish seem to be less susceptible than 0+ fish, possibly due to an acquired immunity resulting from previous exposures. Initial infection loads may be greater on older fish due to greater ventilation rates and/or gill surface areas. However, this host size effect appears to be transitory. In a stock of farmed 0+ salmon, an entire parasitic stage was monitored. This took up to 11 months and only 5–10% of the initially attached glochidia managed to metamorphose and excyst as juvenile mussels. There are apparent differences in host utilisation between salmon and trout in certain rivers. Some trout stocks appear to be under-utilised by M. margaritifera, possibly due to differences in behaviour and/or spawning site. 0+ salmon are the most important hosts in several rivers. However, there are a number of mussel populations located in small streams which have no salmon, and these are entirely trout-dependent. This may be important in terms of conservation, with regard to the recent collapse of migratory trout stocks in Scotland.
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The Extent of, and Causes for, the Decline of a Highly Threatened Naiad: margaritifera margaritifera
Ecology and Evolution of the Freshwater Mussels Unionoida, 2001Co-Authors: Mark R. Young, Peter J. Cosgrove, Lee C. HastieAbstract:margaritifera margaritifera Linn., the freshwater pearl mussel, is distributed from the arctic and temperate regions of western Russia, westwards through Europe to the northeastern seaboard of North America (Fig. 19.1; Jungbluth et al. 1985). Throughout most of its range it has become scarce or threatened, and is listed as “vulnerable” by IUCN (Wells et al. 1983). It is widely believed that it has now become even more threatened (Chesney and Oliver 1998; Young 1991) and the purpose of this chapter is to review evidence for its current status and to identify the causes of its decline.
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physical microhabitat requirements of freshwater pearl mussels margaritifera margaritifera l
Hydrobiologia, 2000Co-Authors: Lee C. Hastie, Philip J Boon, Mark R. YoungAbstract:The spatial distribution patterns of freshwater pearl mussels, margaritifera margaritifera (L.), in the River Kerry, north-western Scotland were investigated, together with their relationships to a number of physical parameters (distance from nearest bank, mean water depth, mean current velocity, substratum descriptors, aquatic vegetation cover). The mussels exhibited a highly contagious, non-random spatial distribution pattern. Adult and juvenile M. margaritifera were found to have broadly similar habitat `preferences', although adults were found over a wider range of physical conditions. Based on computed habitat suitability curves, optimum water depths of 0.3–0.4 m and optimum current velocities of 0.25–0.75 ms-1 at intermediate water levels were observed. River bed substratum characterisitics appear to be the best physical parameters for describing M. margaritifera habitat. Boulder-stabilised refugia, which contain enough sand for burrowing, are ideal microhabitats for juvenile mussels. Adults are able to tolerate silty or muddy conditions for unknown lengths of time, but juveniles are never found in this type of habitat. Substratum-based discriminant function models were used to predict the presence or absence of mussels, with a success rate of 76–92%.
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Growth characteristics of freshwater pearl mussels, margaritifera margaritifera (L.)
Freshwater Biology, 2000Co-Authors: Lee C. Hastie, Mark R. Young, Philip J BoonAbstract:SUMMARY 1. Shell growth in the freshwater pearl mussel, margaritifera margaritifera, was investigated. Three non-linear growth models (i.e. power, logistic and von Bertalanffy) were fitted to Scottish length-at-age data sets and compared. 2. Overall, the von Bertalanffy model outperformed the other two approaches, generating the smallest residuals in eight out of 11 samples (the logistic model provided slightly better fits to the other three). It was concluded that individual M. margaritifera appear to grow in an approximately asymptotic fashion and that the von Bertalanffy equation is an appropriate growth model to fit to freshwater pearl mussel length-at-age data. 3. The ranges in von Bertalanffy parameter estimates observed (k = 0.023‐0.075 year ‐1 , L‘ = 77‐158 mm, to = ‐3.93‐4.33 years) are typical of those reported in northern European populations. 4. Most of the populations investigated had relatively low k-values and high maximum age (Amax) estimates. This feature, which suggests high long-term productivity and less vulnerability to decline (i.e. larger, longer-living mussels produce more offspring), may be a reason why these populations have survived until now. The population which appears to be the most vulnerable (i.e. which has the highest k and lowest Amax) is probably not recruiting adequately at present. 5. An index of absolute growth (mean shell length-at-age) was also used for comparing different populations. Observed between- and within-river differences in mussel growth patterns may be associated with a number of environmental factors, particularly water temperature and productivity. 6. A significant positive relationship between river length and mean mussel length-at-age was observed. In general, mussels grow large in large, cold rivers and vice versa, although there are exceptions which suggest that additional factors may be involved.
Martin Osterling - One of the best experts on this subject based on the ideXlab platform.
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A test for suitable fish hosts for the threatened freshwater pearl mussel (margaritifera margaritifera) prior to reintroduction
2017Co-Authors: Stina Gustafsson, Olle Calles, Martin OsterlingAbstract:A test for suitable fish hosts for the threatened freshwater pearl mussel (margaritifera margaritifera) prior to reintroduction
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The impact of land use on the mussel margaritifera margaritifera and its host fish Salmo trutta
Hydrobiologia, 2013Co-Authors: Martin Osterling, Jan-olov HögbergAbstract:Today, land use impacts a major proportion of all streams. Here, landscape features in corridors along streams and water chemical factors were analyzed in relation to recruitment of the threatened freshwater pearl mussel (margaritifera margaritifera) and its host fish the brown trout (Salmo trutta). Mussel recruitment and trout density were negatively related to forest clear-cuts. Mussel recruitment was negatively related to water color and turbidity. Therefore, the threats to the mussel may be severe, as low mussel recruitment may be caused by direct effects on the juvenile mussels and indirect effects on the host fish. High proportions of lakes and ponds were found to be positive for recruitment and for trout, and deciduous forest was positively related to trout. The combination of investigations at different scales at the landscape level and at in-stream levels may be applicable to find threats to other threatened species. The results indicate that forestry activities may negatively affect recruitment of freshwater pearl mussels and its host fish. Reductions of forestry activities and the retaining of intact quantity and quality of the riparian zones next to streams, both for the mussel and its host fish may be important conservation measures to restore freshwater pearl mussel populations.
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Recruitment of the threatened mussel margaritifera margaritifera in relation to mussel population size, mussel density and host density
Aquatic Conservation-marine and Freshwater Ecosystems, 2012Co-Authors: Bjorn Arvidsson, Jens Karlsson, Martin OsterlingAbstract:Anthropogenic, abiotic factors are considered main causes of recruitment failure of unionid mussels, including the freshwater pearl mussel (margaritifera margaritifera). In this large-scale investi ...
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Anthropogenic changes of brown trout Salmo trutta and the impact on its parasitic mussel margaritifera margaritifera.
2012Co-Authors: Martin Osterling, Håkan SöderbergAbstract:Anthropogenic changes of brown trout Salmo trutta and the impact on its parasitic mussel margaritifera margaritifera.
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The impact of land use on the mussel margaritifera margaritifera and its host fish Salmo trutta.
2012Co-Authors: Martin Osterling, Jan-olov HögbergAbstract:The impact of land use on the mussel margaritifera margaritifera and its host fish Salmo trutta.
Lee C. Hastie - One of the best experts on this subject based on the ideXlab platform.
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Determination of mortality in exploited freshwater pearl mussel (margaritifera margaritifera) populations
Fisheries Research, 2006Co-Authors: Lee C. HastieAbstract:Abstract Estimates of mortality, based on relative numbers of live mussels and empty shells observed were obtained for a sample of seven exploited Scottish freshwater pearl mussel ( margaritifera margaritifera ) populations. Total mortality ( Z ) estimates ranged from 0.058 to 0.189 year −1 and fishing mortality ( F ) estimates ranged from 0.005 to 0.129 year −1 . General trends of increasing Z and F with age were apparent. Pearl fishers generally targeted larger, older mussels. In one heavily exploited population, the Z and F estimates converged, indicating that most of the mortality in older mussels (>50 years) was due to the effects of destructive pearl fishing. Since a complete ban on pearl fishing was introduced in 1998, illegal pearl fishing has continued albeit at a reduced level.
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Characterization of freshwater pearl mussel (margaritifera margaritifera) riverine habitat using River Habitat Survey data
Aquatic Conservation: Marine and Freshwater Ecosystems, 2003Co-Authors: Lee C. Hastie, Mark R. Young, Susan L. Cooksley, F. Scougall, P.j. Boon, Martin J. GaywoodAbstract:1. The feasibility of using River Habitat Survey (RHS) data to describe freshwater pearl mussel (margaritifera margaritifera) macrohabitat in the River Spey, north-east Scotland, was investigated. 2. Mussels were found to be positively associated with a number of RHS variables. These included: boulder/cobble river bed substrates, broken/unbroken standing waves (channel flow types), aquatic liverworts/mosses/lichens and broadleaf/mixed woodland/bankside tree cover. Negative associations with gravel-pebble/silt substrates and emergent reeds/sedges/herbs were also found. 3. Two binary logistic regression models, based on seven and four variables, respectively, were constructed in order to predict the presence/absence of mussels at any given site. Predictive success rates of 83% and 78% were achieved. 4. Another binary logistic regression model, based on four variables, was constructed in order to predict the occurrence of ‘optimal’ M. margaritifera habitat (overall mussel densities ≥ 1 m−2). A predictive success rate of 83% was achieved. 5. The results indicate two potentially important applications of RHS for the conservation management of M. margaritifera: (1) for monitoring the effects of physical changes on extant mussel beds (and predicting their effects on mussel populations), and (2) for determining the habitat suitability of historically occupied sites for re-introductions. Copyright © 2003 John Wiley & Sons, Ltd.
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Freshwater pearl mussel (margaritifera margaritifera) glochidiosis in wild and farmed salmonid stocks in Scotland
Hydrobiologia, 2001Co-Authors: Lee C. Hastie, Mark R. YoungAbstract:Samples of salmonids were taken from six Scottish rivers and examined for freshwater mussel (margaritifera margaritifera (L.)) glochidiosis. The prevalence and magnitude of natural infections observed were comparable to those reported elsewhere. In most rivers, older fish seem to be less susceptible than 0+ fish, possibly due to an acquired immunity resulting from previous exposures. Initial infection loads may be greater on older fish due to greater ventilation rates and/or gill surface areas. However, this host size effect appears to be transitory. In a stock of farmed 0+ salmon, an entire parasitic stage was monitored. This took up to 11 months and only 5–10% of the initially attached glochidia managed to metamorphose and excyst as juvenile mussels. There are apparent differences in host utilisation between salmon and trout in certain rivers. Some trout stocks appear to be under-utilised by M. margaritifera, possibly due to differences in behaviour and/or spawning site. 0+ salmon are the most important hosts in several rivers. However, there are a number of mussel populations located in small streams which have no salmon, and these are entirely trout-dependent. This may be important in terms of conservation, with regard to the recent collapse of migratory trout stocks in Scotland.
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The Extent of, and Causes for, the Decline of a Highly Threatened Naiad: margaritifera margaritifera
Ecology and Evolution of the Freshwater Mussels Unionoida, 2001Co-Authors: Mark R. Young, Peter J. Cosgrove, Lee C. HastieAbstract:margaritifera margaritifera Linn., the freshwater pearl mussel, is distributed from the arctic and temperate regions of western Russia, westwards through Europe to the northeastern seaboard of North America (Fig. 19.1; Jungbluth et al. 1985). Throughout most of its range it has become scarce or threatened, and is listed as “vulnerable” by IUCN (Wells et al. 1983). It is widely believed that it has now become even more threatened (Chesney and Oliver 1998; Young 1991) and the purpose of this chapter is to review evidence for its current status and to identify the causes of its decline.
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physical microhabitat requirements of freshwater pearl mussels margaritifera margaritifera l
Hydrobiologia, 2000Co-Authors: Lee C. Hastie, Philip J Boon, Mark R. YoungAbstract:The spatial distribution patterns of freshwater pearl mussels, margaritifera margaritifera (L.), in the River Kerry, north-western Scotland were investigated, together with their relationships to a number of physical parameters (distance from nearest bank, mean water depth, mean current velocity, substratum descriptors, aquatic vegetation cover). The mussels exhibited a highly contagious, non-random spatial distribution pattern. Adult and juvenile M. margaritifera were found to have broadly similar habitat `preferences', although adults were found over a wider range of physical conditions. Based on computed habitat suitability curves, optimum water depths of 0.3–0.4 m and optimum current velocities of 0.25–0.75 ms-1 at intermediate water levels were observed. River bed substratum characterisitics appear to be the best physical parameters for describing M. margaritifera habitat. Boulder-stabilised refugia, which contain enough sand for burrowing, are ideal microhabitats for juvenile mussels. Adults are able to tolerate silty or muddy conditions for unknown lengths of time, but juveniles are never found in this type of habitat. Substratum-based discriminant function models were used to predict the presence or absence of mussels, with a success rate of 76–92%.