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 European silver eel (Anguilla anguilla L.) migration behaviour in a highly regulated shipping canal

2018 ◽  
Vol 206 ◽  
pp. 176-184 ◽  
Author(s):  
Pieterjan Verhelst ◽  
Raf Baeyens ◽  
Jan Reubens ◽  
Jean-Phillippe Benitez ◽  
Johan Coeck ◽  
...  
Keyword(s):  
Anguilla Anguilla ◽  
Silver Eel ◽  
Migration Behaviour

Challenges for Diadromous Fishes in a Dynamic Global Environment

2009 ◽  
Keyword(s):  
Average Rate ◽  
Underlying Mechanism ◽  
Local Circulation ◽  
Vertical Movements ◽  
Swimming Depth ◽  
Open Sea ◽  
Silver Eels ◽  
Vertical Distributions ◽  
The Baltic ◽  
American Eels

<em>Abstract</em>.-The horizontal and vertical movements of 20 silver American eels <em>Anguilla rostrata </em>migrating through a macrotidal estuary and bay were tracked with hydroacoustic telemetry. Eels initiated their seaward migrations around or shortly after sunset, mostly migrated at night, exhibited no bias for migration on ebb versus flood tides, and swam both with and against tidal currents with little preference for depth. Profiles of eel vertical distributions during transit through the estuary, the bay, and the tidal passages that connected the bay to the open sea differed and differed from analogous profiles for silver European eels <em>A. anguilla </em>transiting the Baltic Sea where tidal forcing is negligible. The underlying mechanism(s) associated with their direction of net displacement appears to be innate, although local circulation features may influence transit speeds and exit routes to the open sea. Our results in combination with published information for both the silver American and the European eel suggest that the horizontal migration speed for both species is relatively invariant, around 0.5 body lengths per second. The rate of ascent/descent of eels exhibiting a change in swimming depth of greater than 5 m could not be estimated with precision from the available records of eel swimming depths. The observed average rate of 0.11 m/s was, however, within the relatively narrow range of the average vertical swimming speeds (0.11-0.18 m/s) reported in the literature for silver eels executing vertical dives.

On the application of models of European eel (Anguilla anguilla) production and escapement to the development of Eel Management Plans: the River Severn

2007 ◽  
Vol 64 (7) ◽  
pp. 1472-1482 ◽  
Author(s):  
M. W. Aprahamian ◽  
A. M. Walker ◽  
B. Williams ◽  
A. Bark ◽  
B. Knights
Keyword(s):  
Reference Conditions ◽  
Anguilla Anguilla ◽  
European Eel ◽  
Silver Eel ◽  
Management Scenarios ◽  
Test Management ◽  
Management Measures ◽  
Silver Eels ◽  
Management Plans ◽  
The Uk

Abstract Aprahamian, M. W., Walker, A. M., Williams, B., Bark, A., and Knights, B. 2007. On the application of models of European eel (Anguilla anguilla) production and escapement to the development of Eel Management Plans: the River Severn. – ICES Journal of Marine Science, 64: 1472–1482. The European eel stock has declined significantly since the 1980s, and the Eel Recovery Plan of the European Commission requires Member States to develop river basin Eel Management Plans (EMPs) that will achieve an escapement of silver eels that equals or exceeds 40% of the escapement biomass that would be produced in the absence of human activities. However, because silver eel escapement is not quantified within the UK, a modelling approach is required to estimate potential and actual escapement, and to assess the likely effects of management measures. We focus on two approaches developed in the UK, the Reference Condition Model (RCM) and the Scenario-based Model for Eel Populations (SMEP), and illustrate how such approaches can be used in EMPs using selected data from the River Severn. The RCM results indicate that the yellow eel population in the River Severn basin may be just 30–40% of the potential density indicated by reference conditions derived from a selection of rivers between the late 1970s and the early 1980s. The challenges of applying a model designed to be as realistic of eel production as possible, and the limited data on natural eel habitat and eel production in the Severn, preclude a SMEP analysis similar to that of the RCM, but simulations based on a simplified basin description and eel survey data from the early 1980s illustrate the potential of this model to assess compliance and test management scenarios.

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

Reconstructing migrations of individual cod (Gadus morhua L.) in the Baltic Sea by using electronic data storage tags

2007 ◽  
Vol 16 (6) ◽  
pp. 526-535 ◽  
Author(s):  
STEFAN NEUENFELDT ◽  
HANS-HARALD HINRICHSEN ◽  
ANDERS NIELSEN ◽  
KEN H. ANDERSEN
Keyword(s):  
Baltic Sea ◽  
Data Storage ◽  
Gadus Morhua ◽  
The Baltic Sea ◽  
Electronic Data ◽  
Data Storage Tags ◽  
The Baltic

Eels at the Edge: Science, Status, and Conservation Concerns

2009 ◽  
Keyword(s):  
Anguilla Anguilla ◽  
Small River ◽  
Biological Characteristics ◽  
Silver Eel ◽  
Biomass Density ◽  
Silver Eels ◽  
Close Proximity ◽  
Males And Females ◽  
Density And Biomass

<em>Abstract.—</em>This paper assesses potential production of premigrant European eels <em>Anguilla anguilla </em>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<sup>–2</sup> [indivdual per 100 m<sup>2</sup>] and 1,352 ± 171 g.100 m–2 in the Frémur River and 3 ± 0.32 ind.100 m–2 and 385 ± 42 g.100 m<sup>–2</sup> 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<sup>–2</sup>/ year) than in the Oir (56.0 g.100 m–2/year). 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.

Evaluation of surgical implantation of electronic tags in European eel and effects of different suture materials

2013 ◽  
Vol 64 (4) ◽  
pp. 324 ◽  
Author(s):  
Eva B. Thorstad ◽  
Finn Økland ◽  
Håkan Westerberg ◽  
Kim Aarestrup ◽  
Julian D. Metcalfe
Keyword(s):  
Data Storage ◽  
Anguilla Anguilla ◽  
Tissue Reaction ◽  
Control Fish ◽  
European Eel ◽  
Silver Eel ◽  
Suture Materials ◽  
Absorbable Sutures ◽  
Internal Reaction ◽  
Electronic Tags

Effects of implanting data-storage tags in European eel, Anguilla anguilla, and the suitability of different suture materials (braided permanent silk, permanent monofilament, absorbable and absorbable antibacterial) were examined. The tags consisted of an electronic unit and three floats on a wire, making them flexible and able to follow the swimming movements of the eel. No mortality occurred, and tagged fish did not differ from the control fish in growth. Sutures were shed or dissolved slowly. After 4 weeks, there was no difference among the groups in the proportion of sutures left. After 6 months, fish with braided silk had largely shed their sutures, fish with monofilament sutures had the majority of sutures left, whereas the fish with absorbable sutures were intermediate in between. Fish with monofilament sutures showed the least-extensive inflammation reactions and fastest wound healing. Antibacterial treatment had no effect on inflammation or healing rates. After 6 months, the tag started to become expelled through the incision in five fish (12%). The internal reaction appeared stronger around the floats, suggesting that the coating material of the floats created a tissue reaction, which should be further investigated. Intraperitoneal implantation appears to be a suitable tagging method for European silver eel, and it is recommended to close incisions using permanent monofilament sutures.

scholarly journals Escapement of eel (Anguilla anguilla) in coastal areas in Sweden over a 50-year period

2012 ◽  
Vol 69 (6) ◽  
pp. 991-999 ◽  
Author(s):  
Jan Andersson ◽  
Ann-Britt Florin ◽  
Erik Petersson
Keyword(s):  
Anguilla Anguilla ◽  
Fishing Effort ◽  
Coastal Areas ◽  
Rapid Decline ◽  
Silver Eel ◽  
Swedish West Coast ◽  
Coastal Fish ◽  
Using Data ◽  
The 1960S ◽  
The Baltic

Abstract Andersson, J., Florin, A.-B., and Petersson, E. 2012. Escapement of eel (Anguilla anguilla) in coastal areas in Sweden over a 50-year period – ICES Journal of Marine Science, 69: 991–999. The escapement of eel from coastal areas in Sweden during the last 50 years was assessed using data from voluntary fishery journals and fishery-independent coastal fish monitoring programmes. It was evident that the level of escapement, determined as catch per unit of effort in numbers, from the Baltic Sea decreased over time, with the most rapid decline occurring in the 1960s and early 1970s, but also in recent years. There were, however, differences in the temporal variability in escapement between areas. Escapement from the northernmost studied site did not change significantly during the last 50 years, while there was a rapid decline in the southern areas. Escapement remained relatively stable between the late 1970s and 2000 however, and escapement at the Swedish west coast, inferred from yellow eel catch per unit of effort, generally increased during the same time. The loss in numbers has to some extent been compensated by an increase in mean weight of silver eel. Possible explanations for the retained level of escapement during the last decades despite the continued reduction in recruitment are discussed. Favourable environmental conditions in combination with a lower fishing effort are suggested as the most probable reasons why the escapement decline has not been more dramatic, but stocking and density-dependent effects cannot be ruled out.

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.

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