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Justin Aaron Benson Barbara Ann Stewart Paul Graeme Close Alan John Lymbery 《水产资源保护:海洋与淡水生态系统》2021,31(3):708-728
- The five global Mediterranean-climate regions are experiencing alarming rates of freshwater biodiversity loss. Although freshwater mussels are recognized as important functional components in aquatic ecosystems, and are among the most threatened faunal groups globally, there has been no synthesis of the plight of this group within these regions.
- Data from the International Union for Conservation of Nature (IUCN) Red List were reviewed to compare the conservation status, threats, and conservation actions needed for freshwater mussel species occurring in Mediterranean-climate regions (med-mussels) with those of other freshwater mussel species globally. The first comprehensive catalogue of med-mussel species was compiled using existing taxonomic literature.
- There are 41 med-mussel species, 30 of which occur in the Mediterranean basin. Many regions have just a single species, and regions where multiple species occur generally only have between one and four species per river basin. Med-mussel species are almost twice as likely to be ‘Imperilled’, are affected by 2.4 times more threats, and require 3.5 times more conservation actions than non-med mussels. In many cases, the exact threats have not been identified.
- In combination with low species richness, this level of imperilment means that Mediterranean-climate regions are at risk of losing the benefits that mussels provide to broader ecosystem functioning. The conservation of med-mussels can be improved by increasing our knowledge of species distributions, including the identification of cryptic species and significant management units, through population genetic work. In addition, recognizing the potential of ‘novel’ habitats and refuge areas could augment the management of this important functional group.
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Igor Popov 《水产资源保护:海洋与淡水生态系统》2020,30(9):1816-1820
- 1. The freshwater pearl mussel, Margaritifera margaritifera, is a threatened species. One of the threats faced by this species is direct extermination by poachers, and therefore some researchers conceal information on the locations of pearl mussel habitats. For example, some researchers do not publish the names of the rivers where pearl mussels occur, whereas other researchers do.
- 2. Concealing the names of rivers containing pearl mussels makes them unknown not only to potential offenders but also to administrators, nature conservation practitioners, and ordinary citizens. As a result, no protection measures are undertaken, which is all the more regrettable as damage to pearl mussel habitats can occur accidentally.
- 3. Concealing details of the location of pearl mussel habitats in publications has an adverse impact on the work of specialists, as they do not have access to enough information to study and analyse the biology and distribution of these molluscs.
- 4. One river with pearl mussels in the Gulf of Finland was initially described anonymously (as ‘River B’). Unfortunately, the river was subject to severe human impact, and the largest aggregation of pearl mussels was almost exterminated in the process of constructing a new electric supply line.
- 5. Concealing information on pearl mussel habitats in the Russian section of the Baltic Sea basin was also shown to have been a poor decision. Although the threat from potential poachers was insignificant because of the low commercial value of pearl mussels, the authorities remained uninformed about the existence of valuable habitats.
- 6. The question of whether the locations of pearl mussel habitats should be concealed or revealed in scientific publications does not have an unambiguous answer and should be considered on a case‐to‐case basis; however, the cases for which disclosure is reasonable seem to be more numerous.
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- 1. Experiments were carried out in the River Spey, Scotland to determine the effects of aquatic weed (Ranunculus spp.) removal on populations of freshwater pearl mussels (Margaritifera margaritifera) and juvenile salmonids (Salmo salar, Salmo trutta) and their river‐bed habitats.
- 2. Physical removal of Ranunculus had no significant impact either on pearl mussels or on salmon and trout fry.
- 3. Regrowth of Ranunculus post‐removal was negligible for one year, indicating that hand‐removal may be an effective control measure.
- 4. Ranunculus roots appear to facilitate substantial depositions of fine sand that are detrimental both to pearl mussels and salmonid fry.
- 5. The rapid spread of invasive Ranunculus is a potential threat to the conservation status of M. margaritifera in the River Spey.
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- 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.
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Igor Popov 《水产资源保护:海洋与淡水生态系统》2021,31(11):3319-3325
- 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.
- 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.
- 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.
- 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.
- 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).
- Surveys using similar methods can help to reveal unknown freshwater mussel populations on other Kuril Islands and on the mainland.
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Genetic structure of Irish freshwater pearl mussels (Margaritifera margaritifera and Margaritifera durrovensis): Validity of subspecies,roles of host fish,and conservation implications 
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下载免费PDF全文 Juergen Geist Evelyn Moorkens Ian Killeen Sarah Feind Bernhard C. Stoeckle Áine O. Connor Ralph Kuehn 《水产资源保护:海洋与淡水生态系统》2018,28(4):923-933
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- 1. Australia has a distinct suite of endemic freshwater mussel species, several of which are restricted to south‐eastern Australia, an intensively modified region supporting much of the nation's population and where pressures on freshwater ecosystems are increasing.
- 2. Surveys were made of 78 sites in the Hunter River system to determine the distribution and abundance of the six mussel species occurring in the region, to identify threatening processes and to locate populations of high conservation value.
- 3. Mussel populations were mainly distributed in the hydrologically stable southern Barrington rivers, where those in the Williams River have the highest conservation value. Strongholds for Hyridella drapeta were found in Wollombi Brook.
- 4. Mussels were not detected at 40% of the sites, some of which supported mussels in the past. These were mainly reaches that have undergone river metamorphosis.
- 5. Where found, most mussel populations had low densities and were highly fragmented. Major threats to these remnant populations are degradation of riparian and instream condition from agricultural activities, extreme climatic events (flood and drought) and the introduced macrophyte, Salvinia molesta.
- 6. While threat mitigation can be achieved by habitat protection and strategies to reconnect mussel populations, managers are largely unaware of this invertebrate group. Formal recognition of regionally threatened mussel populations would do much to focus efforts on conservation.
- 7. The proposed construction of a large dam on the Williams River is a potential threat to the most important mussel populations in the Hunter River system. Copyright © 2009 John Wiley & Sons, Ltd.
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- 1. The Hawkesbury‐Nepean River provides potable water for 5 million people living in the Sydney basin, and water for agricultural and horticultural production that meets most of Sydney's daily needs for fresh food. Anecdotal evidence indicated that numbers of freshwater mussels have seriously declined in much of the river over recent decades.
- 2. A field survey revealed the presence of populations of three species of mussels, Hyridella depressa, Hyridella australis and Velesunio ambiguus in the river. Higher density mussel populations were most common in catchment areas with little human modification to the channel bed or adjacent vegetation communities.
- 3. Levels of disturbance of riparian vegetation and, to a lesser degree, land use, were identified as being strongly associated with the absence of mussels from some reaches.
- 4. Catchment geomorphology was also shown to be relevant to the abundance, population structure and suite of mussel species present in different geomorphic reaches of the river. Absence of mussels was noted from areas where they had been recorded in previous studies. These results demonstrate that mussel species are under threat in the catchment.
- 5. As filter feeders with the ability to remove excess nutrients and bioaccumulate toxic substances, freshwater mussels play an important role in natural remediation processes in freshwater systems.
- 6. The decline in mussel populations in the Hawkesbury‐Nepean River highlights concerns for the overall health of the river system, and supports the need to identify the subsidiary impacts of physical habitat modification in developing both riverine and riparian management strategies.
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- 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.
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- Mahseer (Tor spp., Cyprinidae) are iconic, large-bodied, migratory freshwater fishes of Asian rivers. Long valued as a food source and serving other societal roles, these fishes are severely threatened by a broad range of interacting and escalating human impacts, including dam construction, water pollution, over-exploitation, and habitat destruction. Mahseer fishes are therefore beneficial to people, both directly and as indicators of ecosystem functionality and the associated ecosystem service benefits provided by the rivers that they inhabit.
- A literature review demonstrated that wild mahseer populations have a direct role in 11 of the 36 ecosystem services assessed and are indicative of a further 18 ecosystem services provided by the habitats that support them.
- Recognition of this range of ecosystem service benefits is helpful in describing to non-specialist public and policy-making communities the diversity of values provided by mahseer fishes and their supporting habitats, and hence the importance of their conservation.
- Assessment of the broad range of ecosystem services to which mahseer contribute is an approach that could usefully be applied to promote the benefits of conserving other ‘umbrella’ taxa and the habitats that support them.
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1. Populations of freshwater pearl mussels (Margaritifera margaritifera (L.)) were surveyed in 12 Scottish rivers (selected from those known to contain viable populations). Overall mussel densities in different rivers ranged from 0.27 to 30.01 m−2. Median densities ranged from 2.5 to 14.5 m−2 and a maximum of 398 mussels m−2 was observed in one river. 2. Total population estimates in different rivers ranged from 2000 to 0.9–3.7 million. One population is particularly dense, with an estimated 0.6–1.2 million mussels in a 4‐km stretch of river. 3. Samples from nine populations were taken in order to provide mussel size/age data. Marked differences between size profiles and their corresponding age profiles were observed. It is difficult to interpret the former in terms of recruitment. 4. There were signs of recent recruitment in all of the populations investigated. Large numbers of young mussels (aged ≤20 years) were found in four rivers. The largest proportions at any particular site were 67/219 (30.6%) aged ≤10 years and 191/219 (87.2%) aged ≤20 years, both values being recorded in the same river. 5. The expected predominance of young mussels was not achieved in any population. Presumably, there is considerable underestimation of the youngest age classes owing to biased sampling techniques. However, several populations are thought to be recruiting at levels that are high enough to maintain viability. 6. One population (River F) is the best example of a ‘healthy’, moderately fished, recruiting population and its age profile could be used as a benchmark for future comparisons. 7. The results of this study emphasize the international importance of Scotland in terms of M. margaritifera conservation. However, the small numbers of juveniles found in some Scottish rivers indicates that many populations are vulnerable to decline and, therefore, their conservation status may be threatened in the long term. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献