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1.
- 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.
2.
- 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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Teresa J. Newton Steven J. Zigler James T. Rogala Brian R. Gray Mike Davis 《水产资源保护:海洋与淡水生态系统》2011,21(2):122-131
- 1. Despite a heightened global concern for native mussels, fundamental research on mussel ecology in large rivers is lacking. These gaps in knowledge about where mussels occur, and why, are limiting habitat restoration activities.
- 2. Large‐scale systematic surveys for native mussels in three reaches of the Upper Mississippi River documented mussel communities composed of 16–23 species and ranging from 2.9–4.5 live mussels m?2 that were actively recruiting new cohorts into their populations (87–100% of the species were found as juveniles ?5 years old). Estimates of mean tissue biomass and production in these reaches ranged from 2.1–3.1 g C m?2 and 0.4–0.6 g C m?2 year?1, respectively.
- 3. Mussels filtered a significant amount of water (range, 0.05–0.07 m3 m?2 d?1) over a 480 km reach of the Upper Mississippi River – amounting to a filtration rate of 53.1 million m3 day?1. The filtration rate of mussels as a percentage of river discharge ranged from 0.5–1.4% at high flows (5% exceedance), from 1.5–4.4% at moderate flows (50% exceedance) and from 4.4–12.2% during low flows (95% exceedance).
- 4. Collectively, these data suggest that native mussels play an integral role in this ecosystem by sequestering suspended materials that can be used by other benthic organisms. Published in 2011 by John Wiley and Sons, Ltd.
5.
- 1. The status of host fish populations and fish species richness was investigated at 36 sites of 20 extant freshwater pearl mussel populations, including the drainages of the Elbe, Danube, Rhine, Weser, Aulne, Kemijoki and Tuuloma in Germany, the Czech Republic, France and Finland, by carrying out comparative electrofishings.
- 2. Brown trout (Salmo trutta f. fario) were found to be the available host fish for pearl mussels in all except one of the streams investigated with mean densities of 2861 ha?1 (range 0–8710 ha?1) and a mean biomass of 119 kg ha?1 (range 0–478 kg ha?1). Streams that had been frequently stocked with brown trout had higher trout biomass and densities of host fish than natural populations, but trout stocking had no positive effect in two of the streams investigated.
- 3. Fish species richness ranged from 2 to 16 species per stream and showed a negative correlation with host fish biomass and host fish densities. Undisturbed oligotrophic pearl mussel headwater streams usually only yielded a low number of fish species. Habitat degradation can reduce competitiveness of specialized trout and result in an increased abundance of ubiquitous or atypical species.
- 4. A link between the lack of juvenile pearl mussels and a lack of suitable host fish was only rarely observed. Functional pearl mussel populations with relatively high numbers of juveniles had significantly lower densities and biomass of host fish than pearl mussel populations without recent recruitment.
- 5. This study suggests that 0+ host fish are not necessarily required to sustain functional pearl mussel populations. Low densities of host fish can be compensated by the higher glochidia carrying capacity of older host fish with limited previous contact with pearl mussel glochidia, by the long reproductive period of mussels, and by low mortality rates of juvenile mussels during their post‐parasitic phase.
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Jes Jessen Rasmussen Liselotte Wesley Andersen Trine Just Johnsen Jens Thaulow Marc Anglès d'Auriac Søren Nøhr Thomsen Martin Hesselsøe 《水产资源保护:海洋与淡水生态系统》2021,31(9):2506-2514
- Environmental DNA (eDNA) from water samples is increasingly used to detect the presence and distribution of species in aquatic ecosystems. However, before implementing eDNA in monitoring programmes, various species-specific sampling or analytical issues remain to be resolved in order to minimize frequencies of false-positive and -negative results. For example, empty shells from freshwater pearl mussels (Margaritifera margaritifera) contain extractable DNA (chemical extraction from ground-up shells) suggesting a risk of false-positive samples at stream sites with extinct populations but with empty shell material remaining.
- The aim of this study was to investigate whether empty and naturally degrading shells from M. margaritifera can cause false-positive eDNA signals in water samples.
- Water samples were collected from outdoor stream channels (in Lemming, Denmark) with living freshwater pearl mussels or empty shell material (density ~10 individuals m−2) during a 3-week experimental period. Living freshwater pearl mussels were collected from Hemgravs stream in Sweden and transported to Denmark according to permissions granted by the Swedish and Danish authorities.
- All water samples from stream channels containing empty shells were negative for eDNA indicating that eDNA traces in stream water are most likely to originate from living individuals located upstream of the sampling site. Water samples collected from stream channels containing living individuals of M. margaritifera were consistently positive for eDNA except for one sample (interpreted as a false negative).
- The study shows that positive eDNA signals for freshwater pearl mussels most likely reflect the presence of living individuals. Consequently, we suggest that eDNA should be used to locate remaining population fragments of M. margaritifera in deep and turbulent streams, providing a platform for faster and more efficient decision making when launching investigative and mitigation initiatives.
8.
- 1. This paper documents a diverse, reproducing freshwater mussel community (20 species) in Lower Lake — an impounded, regulated portion of the Little Tallahatchie River below Sardis Dam in Panola Co., Mississippi, USA.
- 2. Despite being regulated and impounded, the lake has a heterogeneous array of habitats that differ markedly in mussel community attributes. Four distinct habitat types were identified based on current velocity and substrate characteristics, representing a gradient from habitats having lotic characteristics to lentic habitats. All four habitat types supported mussels, but habitats most resembling unimpounded, lotic situations (relatively higher current velocity and coarser substrate) had the highest mussel abundance and species density (10.1 mussels m?2, 1.8 species m?2, respectively). Lentic habitats (no flow, fine substrate) were characterized by lower abundance and species density (2.0 mussels m?2, 0.8 species m?2, respectively), but supported mussel assemblages distinctive from lotic habitats.
- 3. Evidence of strong recent recruitment was observed for most species in the lake and was observed in all four habitat types.
- 4. Although impounded and regulated, Lower Lake represents one of the few areas of stable large‐stream habitat in the region. The presence of a diverse, healthy mussel community in this highly modified habitat suggests that a large component of the regional mussel fauna is relatively resilient and adaptable and is limited primarily by the absence of stable river reaches. Management actions that increase stream stability are likely to result in expansion of the mussel fauna and restoration of a valuable component of ecosystem function in this region.
9.
Marie‐Cécile Trouilhé Catherine Souty‐Grosset Frédéric Grandjean Bernard Parinet 《水产资源保护:海洋与淡水生态系统》2007,17(5):520-538
- 1. In France, the distribution of the native white‐clawed crayfish (Austropotamobius pallipes) is restricted, fragmented and mainly located in headwater streams. To conserve this indigenous species, it is necessary to characterize its habitat preferences.
- 2. Seven brooks in the Deux‐Sèvres Département (western France) containing wild populations of A. pallipes were studied to determine its ranges of tolerance to 19 physical and chemical water parameters. On two brooks, the Sèvre Nantaise and the Verdonnière, sites with and without A. pallipes were compared. Each site was sampled twice monthly from November 2002 to November 2004.
- 3. It was found that the white‐clawed crayfish was able to tolerate wide ranges of values of some of the measured parameters. The Magot site harboured the largest A. pallipes population (17.5 crayfish m?2) and had dissolved oxygen concentrations as low as 4.93 mg L?1, while water temperature rose above 20°C for several consecutive days during summer and nitrate concentrations were always found to be above 30 mg L?1. These unusual findings could call into question the status of A. pallipes as a bioindicator of good water quality.
- 4. Principal component analyses (PCA) suggested that an increase of organic matter was a discriminant factor for the presence or absence of A. pallipes. In addition, sites with and without crayfish on the Sèvre Nantaise brook showed showed significant differences (p<0.05) in total organic carbon (TOC), and those on the Verdonnière brook in turbidity and total suspended solids (TSS).
10.
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
11.
Vanina Pasqualini Christine Pergent‐Martini Catherine Fernandez Lila Ferrat Jean E. Tomaszewski Grard Pergent 《水产资源保护:海洋与淡水生态系统》2006,16(1):43-60
- 1. A monitoring system was developed in two Corsican coastal lagoons (Biguglia and Urbino; Corsica, Western Mediterranean).
- 2. Three species of seagrass (Nanozostera noltii, Ruppia cirrhosa and Cymodocea nodosa) were monitored by (i) measuring spatio‐temporal changes in the seagrasses, using fixed structures, (ii) investigating temporal changes in the biological parameters of the seagrasses, and (iii) mapping their distribution by processing aerial images of both lagoons.
- 3. These investigations showed that, while the two lagoons exhibit, a priori, a certain structural homogeneity (ecosystems based on aquatic plants), they function in different ways that are specifically linked to environmental conditions.
- 4. At present, the estimated net production varies from 86 to 469 g C m?2 yr?1 at Biguglia and 190 to 1301 g C m?2 yr?1 at Urbino. These values confirm the richness of these two lagoons, and the interest of using seagrass, by means of regular monitoring, for the conservation and management of coastal lagoons.
12.
- 1. During 2001 and 2002, 12 tributaries of the River Duero basin, north‐west Spain, were sampled. Pearl mussels Margaritifera margaritifera (L.) were located in two of them. Isolated individuals were found in the River Tera, a tributary of the River Esla; and only a few colonies with more than 20 mussels were found in the River Negro.
- 2. All of the specimens found were adults (mean length 95 mm), with juveniles being absent in the river bed. The River Negro plots showed a low median mussel density (0.11 m?2), and that of greatest size consisted of 164 ageing individuals.
- 3. Mussels were mainly located in permanent rivers and in shallow stretches with little flow of water, with heterogeneous substrates and heavily shaded by the riparian woods. The whole basin has well‐conserved rivers with cold oligotrophic water and poor mineralization due to the insolubility of the rocks.
- 4. This relic population has a severely restricted distribution because of a series of large reservoirs in a hydropower complex of the rivers Duero and Esla (caused by the construction of the Ricobayo Dam in 1947) and their negative impact on the rheophilous fish. The mussels of the River Tera have been isolated from the rest of the Duero basin since 1969 (Cernadilla Dam), whereas in the River Negro they have been isolated since 1995 (Agavanzal Dam).
13.
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
14.
Maria C Haws Puá alaikahonihò omau Pascua Robert Howerton Angela Hi'ilei Kawelo Keliiahonui Kotubetey 《Aquaculture Research》2014,45(2):312-319
Abundance, length‐frequencies and distribution of Ruditapes philippinarum (Manila Clams) and Tellina (Quidnipagus) palatum were measured at two beaches in Kāne'ohe Bay, O'ahu, Hawai'i in June, 2010. Abundances had decreased from 866.2 m?2 to 3.4 m?2 for Ruditapes and from 75.5 m?2 to 1.5 m?2 for T. palatum since 1977. Distribution of both species was patchy, but both were most commonly found >40 m from shore. Size frequencies of live clams compared with empty shells suggest that few Ruditapes survive to sexual maturity. A similar trend was not detected for T. palatum. Aquaculture trials of R. philippinarum were conducted at the He'eia and Moli'i traditional Hawaiian fishponds in the same bay. The clams failed to thrive, although triploid and diploid Crassostrea gigas performed well in concurrent trials in the same fishponds. Current lower abundances for wild R. philippinarum could be due to factors related to predation or nutrient limitations. Previously, two large sewage outfalls existed at the surveyed clam bed areas which may have temporarily increased nutrient availability for both wild and cultured clams. Current nutrient levels may inhibit Manila clam growth and recruitment in Kāne'ohe Bay. 相似文献
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During periods when the population size of Japanese anchovy Engraulis japonicus is large, the abundance of 1‐yr olds has been considered to be dependent on the growth and survival processes in the late larval and early juvenile stages in the Kuroshio–Oyashio transition region off northern Japan. Recent growth rates for 10 days before capture of larval and early juvenile E. japonicus were estimated and examined in relation to the surface water temperature and the available copepod density in 1997, 1998 and 1999. Late larval and early juvenile E. japonicus were distributed in the waters with temperature from 15 to 19°C and available prey density from 10 to 1000 mg dry weight (DW) m?2 in the transition region. The late larval growth rates were found to be regulated more strongly by water temperature than by copepod density in the waters <16°C, and more strongly by copepod density than water temperature in the waters <100 mg DW m?2 in the Kuroshio–Oyashio transition region. The recent growth rates decreased from the western waters to the eastern waters in the survey area 140–170°E in 1998, correlating with decreases of food availability to 50–100 mg DW m?2. While in 1999, the recent growth rates were faster in the waters east of 150°E, resulting from eastward expansion of warm water ranges and high available prey density 100–400 mg DW m?2. The key environmental factors regulating late larval growth rate of E. japonicus in the transition region seem to be spatially different between years. 相似文献
16.
- 1. In rearing experiments performed between 1997 and 2007, captive‐bred juvenile mussels were harvested shortly after they had dropped off their host fish, and exposed to different types of cages and holding systems.
- 2. Survival of juveniles ranged from 0 to 92% in the first 4 months, but the mean annual mortality was high in all trials and with all systems. In three trials with sheet cages and sediment boxes exposed to mussel rivers from an initial number of 1440 to 1660 only one to eight mussels reached 4 years of age.
- 3. With the exception of mussels kept in spring water no relationship between growth and survival was observed.
- 4. Low survival rates were obtained in sheet cages exposed to very oligotrophic and highly eutrophic brook stretches. Several natural sites that were lacking recruitment in the wild nevertheless showed good results in the cages.
- 5. All holding systems showed irregular variations in survival rates. Pairs of sheet cages showed no correlation between the survival of mussels in the adjacent cages. In contrast, growth rates were correlated.
- 6. No relationship could be found between the growth or survival in sheet cages at different sites and brooks and the corresponding data on water chemistry.
- 7. The systems tested for rearing young mussels involving a minimal time and effort in the natural habitat were not successful due to the elevated mortality rates of juveniles.
- 8. The rearing success of young pearl mussels in cages in the water flow of mussel rivers gives no information about the suitability of these sites for natural reproduction. Thus, to find potential natural habitats for Margaritifera, it is imperative to survey water quality, sediments and habitat structure. Copyright © 2010 John Wiley & Sons, Ltd.
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Jennifer M. Khan Michael Hart Jack Dudding Clinton R. Robertson Roel Lopez Charles R. Randklev 《水产资源保护:海洋与淡水生态系统》2019,29(8):1202-1215
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18.
Negative effect of zebra mussels on foraging and habitat use by lake sturgeon (Acipenser fulvescens)
- 1. Lake sturgeon (Acipenser fulvescens) are threatened or endangered throughout much of their range. Juvenile sturgeon utilize sandy and silty habitats extensively during their growth. Invasive zebra mussels change the nature of sandy and silty habitats because they settle on and coat the habitat with the shells of living and dead individuals. The potential impacts of this increased habitat complexity on lake sturgeon is unknown.
- 2. Juvenile lake sturgeon habitat choice was assessed in laboratory experiments, and zebra mussel impact on the foraging success of juvenile lake sturgeon on three different prey species was measured.
- 3. Sturgeon foraging on chironomids was virtually eliminated by 95% zebra mussel cover of the sand floor of the foraging arena, and 50% cover reduced foraging significantly. Foraging on more mobile prey items (amphipods and isopods) was essentially eliminated by either 95% or 50% zebra mussel cover of the arena floor. In habitat choice experiments, sturgeon avoided the zebra‐mussel‐covered habitat more than 90% of the time.
- 4. This combination of zebra mussel avoidance and reduced foraging in the presence of zebra mussels may be detrimental to sturgeon restocking programmes utilizing smaller sturgeon in zebra‐mussel‐infested waterways.
19.
- 1. Microhabitat preferences of freshwater mussels and associated substrate characteristics were investigated across a range of geomorphic reaches in the Hawkesbury–Nepean River, Australia.
- 2. The structure of substratum patches available was strongly influenced by geomorphic reach type. In each reach type, mussel distribution was most frequently correlated with coarse sand and a roughness element characteristic for that reach. Roughness elements such as boulders and cobbles create a flow refuge and were linked with mussel size.
- 3. Small mussels tended to be associated with boulder‐stabilized habitats and medium sized mussels with cobble habitats. Large mussels rarely co‐occurred with any particular roughness element. Individual species were strongly linked to geomorphic reach type. This association may be due to species' differences in ability to colonize available microhabitat types.
- 4. The highly tolerant Velesunio ambiguus dominated shale reaches, characterized by fine sediments and human impacts. In contrast, Hyridella depressa dominated in gorges, utilizing small flow refuges among boulders, while H. australis were present in low densities across a range of substrate conditions.
- 5. The persistence of multispecies assemblages in mussel beds throughout the Hawkesbury–Nepean River implies similar niche utilization among species. Partitioning of habitats across species on the basis of size suggests some degree of habitat selection, or differential survival. At the local scale, microhabitat characteristics influenced the size distribution and densities of mussel assemblages. Continuing declines in mussel densities are likely to result from ongoing channel modification and increased siltation resulting from changes to riparian vegetation.