scholarly journals Joint temporal trends in river thermal and hydrological conditions can threaten the downstream migration of the critically endangered European eel

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Elorri Arevalo ◽  
Hilaire Drouineau ◽  
Stéphane Tétard ◽  
Caroline M. F. Durif ◽  
Ola H. Diserud ◽  
...  
Keyword(s):  
Life Cycle ◽  
Water Temperature ◽  
Environmental Changes ◽  
Temporal Trends ◽  
Downstream Migration ◽  
Critically Endangered ◽  
Environmental Cues ◽  
European Eel ◽  
High Discharge ◽  
Silver Eels

AbstractClimate change is modifying the hydrological and thermal regimes of rivers worldwide, threatening the triggering of organisms’ key life-cycle processes. European eel (Anguilla anguilla) is a critically endangered fish species that migrates over several thousand kilometres between its rearing habitats in continental waters of Europe and North Africa and its spawning area in the Sargasso Sea. Downstream migration of adult eels occurs during periods of decreasing river water temperature associated with high discharge but changes in these environmental cues may affected eel migratory conditions. An innovative multivariate method was developed to analyse long-term datasets of daily water temperature, discharge and eel passage in two European rivers. Over the past 50 years, water temperature and discharge increased in both rivers during the downstream migration period from August to November. Silver eels preferentially migrated at temperatures between 10 and 20 °C combined with high discharge. Environmental changes have resulted in the migration of silver eels under warmer water temperatures. This example illustrates how the changes in environmental cues have led to a growing mismatch between the migratory conditions preferentially selected and those actually used, which may threaten the completion of the eel’s life cycle and ultimately the persistence of this already critically endangered species.

scholarly journals European eel (Anguilla anguilla): prediction of spawner escapement from continental population parameters

2000 ◽  
Vol 57 (8) ◽  
pp. 1627-1635 ◽  
Author(s):  
Eric Feunteun ◽  
Anthony Acou ◽  
Pascal Laffaille ◽  
Antoine Legault
Keyword(s):  
Population Structure ◽  
Environmental Factors ◽  
Anguilla Anguilla ◽  
Downstream Migration ◽  
The Other ◽  
European Eel ◽  
Population Parameters ◽  
Sedentary Population ◽  
Continental Population ◽  
Silver Eels

This 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,.

scholarly journals Just go with the flow? Route selection and mortality during downstream migration of silver eels in relation to river discharge

2007 ◽  
Vol 64 (7) ◽  
pp. 1437-1443 ◽  
Author(s):  
Henrice M. Jansen ◽  
Hendrik V. Winter ◽  
Maarten C. M. Bruijs ◽  
Harry J. G. Polman
Keyword(s):  
River Discharge ◽  
Radio Telemetry ◽  
Anguilla Anguilla ◽  
Downstream Migration ◽  
European Eel ◽  
Route Selection ◽  
Migration Routes ◽  
Silver Eel ◽  
Silver Eels ◽  
The Impact

Abstract Jansen, H. M., Winter, H. V., Bruijs, M. C. M., and Polman, H. J. G. 2007. Just go with the flow? Route selection and mortality during downstream migration of silver eels in relation to river discharge. – ICES Journal of Marine Science, 64: 1437–1443. The European eel (Anguilla anguilla) has been in steep decline for several decades. Fisheries and hydropower-induced mortality presumably play an important role during the downstream migration of silver eels, and downstream-migrating silver eels must make various navigation and route-selection decisions to reach the sea. We examined the influence of river discharge on route selection of silver eels. To quantify the impact of hydropower and fisheries on silver eel mortality, radio-telemetry experiments were performed in the River Meuse in 2002 and 2004, surgically implanting 300 silver eels with Nedap-transponders. Route selection and passage behaviour near detection stations was assessed. Silver eels were distributed over the alternative migration routes in the river in proportion to the discharge until the silver eels reached the entrance to the turbines. The eels altered their behaviour when approaching the turbines of hydropower plants and showed stationary and recurrent behaviour. We discuss the consequences of this on route selection and mortality rates caused by hydropower facilities and fisheries.

Direct and indirect impacts of pumping station operation on downstream migration of critically endangered European eel

2018 ◽  
Vol 26 (1) ◽  
pp. 76-85 ◽  
Author(s):  
Jonathan D. Bolland ◽  
Leona A. Murphy ◽  
Robert J. Stanford ◽  
Natalie V. Angelopoulos ◽  
Nicola J. Baker ◽  
...  
Keyword(s):  
Downstream Migration ◽  
Critically Endangered ◽  
European Eel ◽  
Pumping Station ◽  
Direct And Indirect Impacts ◽  
Indirect Impacts

scholarly journals Silver eel mortality during downstream migration in the River Meuse, from a population perspective

2007 ◽  
Vol 64 (7) ◽  
pp. 1444-1449 ◽  
Author(s):  
Hendrik V. Winter ◽  
Henrice M. Jansen ◽  
André W. Breukelaar
Keyword(s):  
Anguilla Anguilla ◽  
Mortality Rates ◽  
Downstream Migration ◽  
European Eel ◽  
Silver Eel ◽  
The Past ◽  
River Meuse ◽  
Silver Eels ◽  
The Impact ◽  
Insight Into

Abstract Winter, H. V., Jansen, H. M., and Breukelaar, A. W. 2007. Silver eel mortality during downstream migration in the River Meuse, from a population perspective. – ICES Journal of Marine Science, 64: 1444–1449. The European eel (Anguilla anguilla) population has decreased sharply over the past few decades owing to a combination of many factors. To determine the impact of hydropower and fisheries during the downstream migration of silver eel in the River Meuse, telemetry experiments were performed during the years 2002–2006, using 18 detection stations (NedapTrail-System®) in the river and two at the entrance to the hydropower turbines. Recaptures in fisheries were used to assess fisheries mortality. In all, 300 silver eels were surgically implanted with Nedap-transponders. For each stretch between subsequent stations, mortality rates were assessed and related to the different factors. However, to determine the overall effect on the escapement of silver eels from the River Meuse, insight into the distribution of silver eels in the entire catchment of the River Meuse is required. At two locations, mark-recapture experiments in 2002 revealed that the estimated number of migrating silver eels increased strongly in a downstream direction, suggesting that a large proportion of silver eels start their migration from the downstream stretches and tributaries of the River Meuse. Approaches and monitoring requirements that can be used to determine the impact on silver eel populations in a river basin are discussed.

scholarly journals Responses of Benthic Macroinvertebrate Communities of Two Tropical, High-Mountain Lakes to Climate Change and Deacidification

Diversity ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 243
Author(s):  
Javier Alcocer ◽  
Luis A. Oseguera ◽  
Diana Ibarra-Morales ◽  
Elva Escobar ◽  
Lucero García-Cid
Keyword(s):  
Climate Change ◽  
Species Richness ◽  
Water Temperature ◽  
Water Level ◽  
Environmental Changes ◽  
Mountain Lakes ◽  
High Mountain ◽  
Macroinvertebrate Communities ◽  
High Mountain Lakes ◽  
La Luna

High-mountain lakes are among the most comparable ecosystems globally and recognized sentinels of global change. The present study pursued to identify how the benthic macroinvertebrates (BMI) communities of two tropical, high mountain lakes, El Sol and La Luna, Central Mexico, have been affected by global/regional environmental pressures. We compared the environmental characteristics and the BMI communities between 2000–2001 and 2017–2018. We identified three principal environmental changes (the air and water temperature increased, the lakes’ water level declined, and the pH augmented and became more variable), and four principal ecological changes in the BMI communities [a species richness reduction (7 to 4), a composition change, and a dominant species replacement all of them in Lake El Sol, a species richness increase (2 to 4) in Lake La Luna, and a drastic reduction in density (38% and 90%) and biomass (92%) in both lakes]. The air and water temperature increased 0.5 °C, and lakes water level declined 1.5 m, all suggesting an outcome of climate change. Contrarily to the expected acidification associated with acid precipitation, both lakes deacidified, and the annual pH fluctuation augmented. The causes of the deacidification and the deleterious impacts on the BMI communities remained to be identified.

scholarly journals Signatures of natural selection between life cycle stages separated by metamorphosis in European eel

BMC Genomics ◽  
2015 ◽  
Vol 16 (1) ◽  
Author(s):  
J. M. Pujolar ◽  
M. W. Jacobsen ◽  
D. Bekkevold ◽  
J. Lobón-Cervià ◽  
B. Jónsson ◽  
...  
Keyword(s):  
Life Cycle ◽  
Natural Selection ◽  
European Eel ◽  
Life Cycle Stages

Branchial expression of an aquaporin 3 (AQP-3) homologue is downregulated in the European eelAnguilla anguillafollowing seawater acclimation

2002 ◽  
Vol 205 (17) ◽  
pp. 2643-2651 ◽  
Author(s):  
Christopher P. Cutler ◽  
Gordon Cramb
Keyword(s):  
Northern Blot Analysis ◽  
Transcript Abundance ◽  
European Eel ◽  
Aquaporin 3 ◽  
Quantitative Studies ◽  
Silver Eels ◽  
Polymerase Chain ◽  
Seawater Acclimation ◽  
Yellow Eels ◽  
Specific Mrna

SUMMARYA cDNA encoding the homologue of mammalian aquaporin 3 (AQP-3) was isolated by reverse transcription—polymerase chain reaction from the gill of the European eel. The derived amino acid sequence shares 67-70% homology with other vertebrate AQP-3 homologues. Northern blot analysis revealed two AQP-3-specific mRNA species of 2.4 kb and 7 kb. AQP-3 mRNA is expressed predominantly in the eye, oesophagus, intestine (as found in mammals) and the gill; no expression could be demonstrated in the stomach and only low and sporadic levels in the kidney. Quantitative studies demonstrated that,following the 3-week acclimation of freshwater (FW)-adapted yellow and silver eels to seawater (SW), transcript abundance in the gill was reduced by 76% and 97%, respectively. The half time of branchial AQP-3 mRNA downregulation in yellow eels was approximately 10 h, with a maximal 94% decrease in expression after 2 days in SW (compared to time-matched FW controls). However, in fish acclimated to SW for more than 4 days, the fall in AQP-3 mRNA abundance recovered slightly, such that after 3 weeks, expression was 16% of that in time-matched FW controls. The potential roles for this aquaporin isoform in water or solute transport in the eel gill are discussed.

scholarly journals When will the eel recover? A full life-cycle model

2007 ◽  
Vol 64 (7) ◽  
pp. 1491-1498 ◽  
Author(s):  
Mårten Åström ◽  
Willem Dekker
Keyword(s):  
Life Cycle ◽  
Distribution Area ◽  
European Eel ◽  
Life Cycle Model ◽  
Cycle Model ◽  
Glass Eel ◽  
Full Life Cycle ◽  
Long Run ◽  
Spawning Stock ◽  
Full Life

Abstract Åström M., and Dekker W. 2007. When will the eel recover? A full life-cycle model. – ICES Journal of Marine Science, 64: 000–000: –. The European eel population has declined over the past decades in most of its distribution area, and the stock is outside safe biological limits. The EU has taken up the challenge to design a management system that ensures the escapement of 40% of spawning-stock biomass, relative to unexploited, unpolluted circumstances in unobstructed rivers. This ultimately aims to restore the spawning stock to a level at which glass eel production is not impaired, i.e. to restore to full historical glass eel recruitment. To explore the trajectory from the current depleted state to full recruitment recovery, we developed a simple model of stock dynamics, based on a simplified stock–recruitment relationship and the conventional dynamic pool assumptions. Recruitment trajectories under different future fishery regimes are explored, for the medium (one generation time) and long time-span (until full recruitment recovery). Reducing fisheries to zero, recovery is expected within ∼80 years, whereas under an ultimately sustainable fishing regime of just 10% of the current rate of fishing mortality, recovery may take more than 200 years. Moreover, management regimes, apparently leading to slight recovery of the stock in the coming 5–15 years, might still be unsustainable in the long run.

scholarly journals Hard times for catadromous fish: the case of the European eel (Anguilla anguilla, L. 1758)

2021 ◽  
Vol 12 (2) ◽  
Author(s):  
Cinzia Podda ◽  
Andrea Sabatini ◽  
Francesco Palmas ◽  
Antonio Pusceddu
Keyword(s):  
Life Cycle ◽  
Anguilla Anguilla ◽  
Cultural Value ◽  
European Eel ◽  
Migration Patterns ◽  
Habitat Occupancy ◽  
Hard Times ◽  
Ancient Times ◽  
And Migration ◽  
Anthropogenic Threats

Catadromous fish species are very important organisms for their ecological, economical, and cultural value. For its complex life species catadromous fish result in worldwide decline since the beginning of the 20th century. Among the most iconic catadromous species, the European eel Anguilla anguilla L. 1758 has aroused considerable interest since very ancient times. Because, to date, many aspects of their life cycle remain relatively unknown, to implement our knowledge about the main natural and anthropogenic threats to its survivorship and identify possible solutions to preserve it, in this narrative review, we present the state of the knowledge about the life cycle, habitat occupancy, recruitment, and migration patterns of the European eel and about the major threats most likely have contributed to the decline of eels’ populations.

scholarly journals Growth potential can affect timing of maturity in a long-lived semelparous fish

2018 ◽  
Vol 14 (7) ◽  
pp. 20180269 ◽  
Author(s):  
Kazuki Yokouchi ◽  
Françoise Daverat ◽  
Michael J. Miller ◽  
Nobuto Fukuda ◽  
Ryusuke Sudo ◽  
...  
Keyword(s):  
Anguilla Anguilla ◽  
Growth Conditions ◽  
Growth Potential ◽  
Individual Growth ◽  
Growth Trajectories ◽  
Female Size ◽  
European Eel ◽  
Growth And Survival ◽  
Silver Eels ◽  
Reproduction Cost

Many diadromous fishes such as salmon and eels that move between freshwater and the ocean have evolved semelparous reproductive strategies, but both groups display considerable plasticity in characteristics. Factors such as population density and growth, predation risk or reproduction cost have been found to influence timing of maturation. We investigated the relationship between female size at maturity and individual growth trajectories of the long-lived semelparous European eel, Anguilla anguilla . A Bayesian model was applied to 338 individual growth trajectories of maturing migration-stage female silver eels from France, Ireland, the Netherlands and Hungary. The results clearly showed that when growth rates declined, the onset of maturation was triggered, and the eels left their growth habitats and migrated to the spawning area. Therefore, female eels tended to attain larger body size when the growth conditions were good enough to risk spending extra time in their growth habitats. This flexible maturation strategy is likely related to the ability to use diverse habitats with widely ranging growth and survival potentials in the catadromous life-history across its wide species range.

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