Disrupted downstream migration behaviour of European silver eels (Anguilla anguilla, L.) in an obstructed river

2016 ◽  
Vol 99 (10) ◽  
pp. 779-791 ◽  
Author(s):  
Marc L. Besson ◽  
Thomas Trancart ◽  
Anthony Acou ◽  
Fabien Charrier ◽  
Virgile Mazel ◽  
...  
Keyword(s):  
Anguilla Anguilla ◽  
Downstream Migration ◽  
Migration Behaviour ◽  
Silver Eels

Migration behaviour of silver eels (Anguilla anguilla) in a large estuary of Western Europe inferred from acoustic telemetry

2014 ◽  
Vol 137 ◽  
pp. 23-31 ◽  
Author(s):  
Elise Bultel ◽  
Emilien Lasne ◽  
Anthony Acou ◽  
Julien Guillaudeau ◽  
Christine Bertier ◽  
...  
Keyword(s):  
Acoustic Telemetry ◽  
Western Europe ◽  
Anguilla Anguilla ◽  
Migration Behaviour ◽  
Silver Eels

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,.

The migration behaviour of European silver eels (Anguilla anguilla) released in open ocean conditions

2015 ◽  
Vol 66 (2) ◽  
pp. 145 ◽  
Author(s):  
K. Wysujack ◽  
H. Westerberg ◽  
K. Aarestrup ◽  
J. Trautner ◽  
T. Kurwie ◽  
...  
Keyword(s):  
Atlantic Ocean ◽  
Anguilla Anguilla ◽  
Large Female ◽  
Sargasso Sea ◽  
Migration Routes ◽  
Long Distance ◽  
European Continent ◽  
Vertical Movements ◽  
Migration Behaviour ◽  
Silver Eels

Despite some recent progress, there are still large gaps of knowledge about migration routes and behaviour of European eels, Anguilla anguilla, during their long-distance oceanic migration. To achieve a better understanding of the migration behaviour, 28 large female silver eels were equipped with pop-up satellite transmitters and released at three different locations in the north-eastern Atlantic Ocean and in the Sargasso Sea. The study covers tracking periods between 7 and 92 days. The distance between release point and estimated pop-up position ranged from 40 to 1000km, the mean minimum migration speeds from 1.5 to 17.0km day–1. The eels consistently conducted distinct diel vertical movements (DVM) with daily amplitudes of more than 300m and maximum diving depths of more than 1000m. Eels released in the Sargasso Sea used greater depths and a broader temperature range than individuals released in the Atlantic Ocean closer to the European continent. At least two eels were clearly preyed upon. The transmitters ascended in a considerable range of directions from the release points. Hence, the results of the study did not allow clear conclusions about the detailed location of the spawning site and on the routes of the eels to the spawning grounds.

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.

scholarly journals Silver eel migration behaviour in the Baltic

2007 ◽  
Vol 64 (7) ◽  
pp. 1457-1462 ◽  
Author(s):  
Håkan Westerberg ◽  
Ingvar Lagenfelt ◽  
Henrik Svedäng
Keyword(s):  
Baltic Sea ◽  
Data Storage ◽  
Anguilla Anguilla ◽  
Light Level ◽  
Thermocline Depth ◽  
Silver Eel ◽  
Migration Behaviour ◽  
Swimming Depth ◽  
Silver Eels ◽  
The Baltic

Abstract Westerberg, H., Lagenfelt, I., and Svedäng, H. 2007. Silver eel migration behaviour in the Baltic. – ICES Journal of Marine Science, 64: 1457–1462 Female silver eels (Anguilla anguilla L.) were tagged with data storage tags and released in the Baltic Sea at the same time at a single site on the east coast of Sweden. Data on temperature, light, and depth were obtained from six eels, continuous records for 71 d at sea. The swimming behaviour was similar for all fish, almost stereotyped: swimming activity was between dusk and dawn, starting at a light level corresponding to civic twilight and ending in the morning at generally the same light level. During daylight, the eels rested on the seabed at depths of 2–36 m. Swimming depth was typically close to the surface: up to 95% of swimming time was spent within 0.5 m of the surface. Short dives at irregular intervals (some 1–2 h−1) were made down to the thermocline depth, or occasionally, to the seabed. The duration of such dives were typically 5–10 min. Although only a few days at liberty, the eels had migrated a considerable distance between recapture and release sites, indicating a mean rate of travel of ∼16 km d−1. The recapture positions suggested unidirectional movements towards the southwestern Baltic Sea, i.e. close to the straits leading to the ocean, supporting a belief that the recorded movements were related to eel spawning migratory behaviour.

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 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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