333 research outputs found
The yellow European eel (Anguilla anguilla L.) may adopt a sedentary lifestyle in inland freshwaters
No full textWe analysed the movements of the growing yellow phase using a long-term mark–recapture programme on European eels in a small catchment (the Frémur, France). The results showed that of the yellow eels (>200 mm) recaptured, more than 90% were recaptured at the original marking site over a long period before the silvering metamorphosis and downstream migration. We conclude that yellow European eels >200 mm may adopt a sedentary lifestyle in freshwater area, especially in small catchment
Differentiable production and condition indices of premigrant eels (Anguilla anguilla) in two Atlantic coastal catchments of France
No full textThis paper assesses potential production of premigrant European eels Anguilla anguilla based on analysis of sedentary eel populations in two small river systems in western France that are in close proximity. Abundance and biological characteristics were evaluated from electrofishing surveys conducted in three years in September and October, before the catadromous migration of silver eels. Mean density and biomass density of the eel population differed greatly between the systems (39 ± 6 ind.100 m ± 2 and 1352 ± 171 g.100 m ± 2 in the Frémur River and 3 ± 0.32 ind.100 m ± 2 and 385 ± 42 g.100 m ± 2 in the Oir River). Premigrants were dominated by males in the Frémur (85.8%) and by females in the Oir (79.0%). Estimated premigrant biomass density was 4.5-fold higher in the Frémur (254.5 g.100 m ± 2.year ± 1) than in the Oir (56.0 g.100 m ± 2.year ± 1). Mean Fulton’s K condition factor was significantly higher for both sexes in the Oir (0.20 ± 0.004 and 0.20 ± 0.003 for males and females, respectively) than in the Frémur (0.17 ± 0.002 and 0.17 ± 0.004, respectively). The large differences in densities and biological characteristics of eels from neighboring catchments suggest that huge variability of both quantity and quality of silver eel production can be expected at the scale of the European stock
Patterns of silver eel (Anguilla anguilla L.) sex ratio in a catchment
No full textChanges in the numbers and size-class structure of European silver eels, Anguilla anguilla, in the River Fre´mur (France) were examined over a 9-year period after installation of downstream eel passes. The number of silver eels migrating downstream peaked in 1999, then decreased strongly and steadily after 2000, reaching relatively low levels. At the same time, a gradual shift in the silver eel sex ratio from a dominance of males (size from 270 to 442 mm, age from 3 to 6 years) to females (size from 366 to 1112 mm, age from 4 to 9 years) was recorded. Possible explanations for the escapement patterns observed are environmental sex determination and the installation of eel passes on the main hydraulic engineering structures in 1992 and 1996
Migration pattern of silver eel (Anguilla anguilla, L.) in an obstructed river system.
No full textThe downstream migration of European silver eels in the River Frémur was examined to determine the potential effects of the numerous migration barriers that exist on waterways in western France. The Frémur has a 14 m high dam which creates a 3 · 106 m3 water supply reservoir, 6 km from tidal limit. Based on 8-year records (1996–2004) of migrant silver eels captured in a Wolf trap located about 1 km below the dam, the influence of this dam on the migration was examined. These records indicate that 91% of silver eels were captured when the dam was overtopped (i.e. when the water reservoir was full). The timings of the overflow periods varied greatly between years mainly because they are function of the duration of the filling period which in turn is dependent on the level of summer water abstraction and annual hydrological conditions. Consequently, migration periods occurred at variable dates (between November and April) which is late in comparison with nonobstructed European river systems (generally between August and December). During overflow periods the migration of silver eels increased markedly during rain events (increasing river flow). This indicates that flow flushes, are essential so that settled silver eels can orientate themselves and pass over the dam. The hypothesis of a ‘dam effect’ that could stop temporarily or permanently some of silver eels in the reservoir is discussed. Finally, the influence of the migration delays on the condition of silver eels is considered
Towards a standardized characterization of the potentially migrating silver European eel (Anguilla anguilla L.)
No full textWe defined a standardized method for discriminating candidate silver eels
that may undergo catadromous migration in the following season from the sedentary
fraction of a population. A combination of two qualitative criteria (state of differentiation
of the lateral line and colour contrast) and one quantitative criterion (Ocular Index
OI) was used to determine the development toward silvering. In the non-migratory
phase, we found a gradient of the three criteria between yellow (0 criterion), presilver
(1 to 2 criteria) and silver (3 criteria) eels. In the migrant phase, silver eels had ended
their metamorphosis process and were characterized at the same time by the presence
of the 3 silvering criteria. A mark-recapture survey using PIT-tags provided evidence
that only identified silver eels (3 silvering criteria present) in the catchment actually
emigrated the following season. Moreover, the use of a single criterion of silvering
among the three generated large variation in the estimated proportion of candidates for
emigration which varied between –22% and +63 %. Such a result confirmed that a
multicriteria approach is needed to characterize in a standard way the potentially migrating
silver eel
European eel (Anguilla anguilla): prediction of spawner escapement from continental population parameters
No full textThis paper describes the assessment of silver European eel (Anguilla anguilla) escapement based on a “sedentary” population fraction analysis in a 60-km2 watershed of northern Brittany (France). Downstream migration fluxes were monitored using eel traps and related to environmental factors. Intensive electrofishing and fyke-net fishing were conducted to assess eel biomass, densities, and population structure. A total of 564 eels, including 81 silver eels, were PIT tagged. In 1996, 616 eels were caught in the catchment including 68 silver eels (11%). During the following downstream migration period, 12 of the PIT-tagged silver eels, among a total of 678, were recaptured in the downstream traps. Seven were recaptured in the catchment in 1997. It was shown that (i) only about 20% of the silver eels present in the catchment emigrated during the following year, (ii) 12% stayed in the catchment including two (3.4%) that recovered yellow eel characteristics, and (iii) the other eels either died or settled in the catchment but were not recaptured. It was also estimated that 2% (650 eels) of the population (34 000 eels) among 3000 silver eels considered “emigration candidates” emigrated each year
Environmental determinism of year to year recruitment variability of European eel in a small coastal catchment, the Frémur river, north-west France
No full textThe influence of environmental factors (mainly the river flow) on the year-to-year variability of European eel Anguilla anguilla fluvial recruitment in a small coastal River (north-west France) was examined. A comprehensive survey of catches from fixed traps at two weirs located at 4·5 km (Pont es Omnes Dam) and 6·0 km (Bois Joli Dam) above the river mouth was carried out between 1997 and 2004. Young pigmented elvers (mean ± s.d. total length, 133·7 ± 29·6 mm) were recruited in eel-passes from February to October, but the main runs followed a modal curve from April to September with a peak centred in May to June. Catches varied greatly between years, from 381 to 26 765 elvers. For each trap, a positive linear relationship between monthly mean river flow that preceded the maximal intensity of captures and annual total catches was observed. These relationships explained 73·1% (P <0.01)
and 89·0% (P <0.001) of the year-to-year variability of the recruitment observed in the Pont es Omnes and Bois Joli traps respectively. A significant increase in river flow at the beginning of the migration peak would thus trigger a greater proportion of A. anguilla settled in the estuary
and in the downstream zone of the Fremur River to begin their freshwater colonization. The physicochemical roles of changes in river discharge in stimulating upstream migration are discussed. It is concluded that fluvial recruitment in the Fremur River is mainly determined by environmental factors
Unraveling the Chemosensing Mechanism by the 7‑(Diethylamino)coumarin-hemicyanine Hybrid: A Ratiometric Fluorescent Probe for Hydrogen Peroxide
No full textThe hemicyanine hybrid containing the 7-(diethylamino)coumarin
(ACou) donor attached to the cationic indolenium (Ind) acceptor through
a vinyl linkage (ACou-Ind) represents a classic ratiometric fluorescent
probe for detecting nucleophilic analytes, such as cyanide and reactive
sulfur species (RSS), through addition reactions that disrupt dye
conjugation to turn off red internal charge transfer (ICT) fluorescence
and turn on blue coumarin emission. The chemosensing mechanism for
RSS detection by ACou-Ind suggested in the literature has now been
revised. Our studies demonstrate that thiolates react with ACou-Ind
through conjugate addition to afford C4-SR adducts that lack coumarin
fluorescence due to photoinduced electron transfer quenching by the
electron-rich enamine intermediate. Thus, ACou-Ind serves as a turn-off
probe through loss of red ICT fluorescence upon RSS addition. The
literature also suggests that blue coumarin emission of thiolate adducts
is enhanced in the presence of reactive oxygen species (ROS) due to
ROS-mediated cellular changes. Our studies predict that such a scenario
is unlikely and that thiolate adducts undergo oxidative deconjugation
in the presence of H2O2, the pervasive ROS.
Under basic conditions, H2O2 also reacts directly
with ACou-Ind to generate intense coumarin fluorescence through an
epoxidation process. The relevance of our chemosensing mechanism for
ACou-Ind was assessed within live zebrafish, and implications for
the utility of ACou-Ind for unraveling the interplay between RSS and
ROS are discussed
Dental students’ perception of a self-preference musical mobile app used as a relaxing tool in the clinical setting
No full textBackground: Diverse music activities may reduce stress and enhance well-being. However, using a musical mobile health application (app) as an intervention during dental treatment has not yet been established. Hence, a self-preference musical mobile app (ACOU@PLAY) has been created for use in clinical settings. Purpose: This study aims to assess the quality of the ACOU@PLAY app as a relaxing tool for dental students and compare the results with patients’ opinions. Methods: A total of 53% (n = 38) dental students and 47% (n = 35) patients were recruited to use the self-preference musical mobile app (ACOU@PLAY) for 10 minutes and watch a 5-minute pre-recorded video. Then, an evaluation was performed using a validated tool, the modified user version Mobile App Rating Skill (uMARS), which included a demographic survey. The uMARS questionnaire consists of five domains (engagement, functionality, aesthetics, information, and app subjective quality) using a 5-point Likert scale. Results: The average quality score of the app was 3.96 ± 0.509. The app received its highest rating for the information domains, with a mean score of 4.14 ± 0.577, and its lowest for subjective quality, with a mean score of 3.63 ± 0.565. Notable differences were observed in the ratings for engagement (p = 0.008) and aesthetics (p = 0.035) between dental students and patients, as well as significant differences in ratings based on gender in the domains of engagement (p = 0.007), functionality (p = 0.018), and aesthetics (p = 0.021). Conclusion: The self-preference musical mobile app (ACOU@PLAY) is well accepted by dental students and favored by patients with adequate qualities to be used in clinical settings
Use of a reciprocal transplant study to measure the rate of plant community change in a tidal marsh along a salinity gradient
No full textFreshwater reclaimed marshes along the European Atlantic coast are highly suitable for European eels (Anguilla anguilla). However, European eel stocks have declined, and the coastal marshes have been subjected to major disturbances. The objective of our study was to analyze the processes governing patterns of European eel microhabitat distribution of four eel size classes (from ,160 mm to .360 mm) in a reclaimed marsh (France). Analyses were conducted using artificial neural network (ANN) techniques and ecological profiles. Our ANN results showed that eel densities were significantly related to three major influencing variables: the width of ditch section, the silt depth, and the density of emergent plants. Such ecological profiles were significantly different between small (,240 mm) and large eels (.360 mm): small eels were more widespread than large eels. Large eels were absent or at low densities in shallow ditches with a high aquatic plant cover obstructing the water column and a large quantity of silt. These characteristics seem to define the ditches not directly connected with the main river where dredging operations were rare. Management of regular dredging operations in the channels by maintaining a mosaic of permanent aquatic habitats and avoiding the heavy silt loads in most ditches should be promoted. This dredging operation was probably one of the most promising ways for restoring inland eel stocks
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