scholarly journals European Eel (Anguilla anguilla) stock size, anthropogenic mortality and silver eel escapement in the Netherlands 2006-2020

2021 ◽  
Author(s):  
T. van der Hammen ◽  
◽  
F. Soudijn ◽  
J. Volwater ◽  
J.C. van Rijssel ◽  
...  
Keyword(s):  
The Netherlands ◽  
Anguilla Anguilla ◽  
European Eel ◽  
Silver Eel ◽  
Stock Size

scholarly journals Mortality of silver eel (Anguilla anguilla) migrating downstream through a small hydroelectric plant on the Drawa River in northern Poland

2016 ◽  
Vol 24 (2) ◽  
pp. 69-75 ◽  
Author(s):  
Piotr Dębowski ◽  
Rafał Bernaś ◽  
Michał Skóra ◽  
Jacek Morzuch
Keyword(s):  
Acoustic Telemetry ◽  
Hydroelectric Plant ◽  
Anguilla Anguilla ◽  
European Eel ◽  
Upstream Migration ◽  
Silver Eel ◽  
Passive Integrated Transponder ◽  
Northern Poland ◽  
Hydroelectric Plants ◽  
Pass Through

Abstract The European eel, Anguilla anguilla L., is an endangered species. Barriers to its downstream spawning migration are one of the greatest threats this species faces. There are hundreds of hydroelectric plants (HEP) on rivers in Poland (> 600), and thousands throughout Europe. Eel that pass through HEP turbines as they migrate downstream suffer high mortality, but this depends mainly on local and technical conditions. Silver eel mortality was estimated and the possibility of the fish bypassing the turbines was studied between November 2013 and June 2014 at a typical HEP in northern Poland. Two telemetry methods were used with 49 eel: passive integrated transponder (PIT) system and acoustic telemetry. Fifty five percent of eel migrated downstream in fall 2013, soon after their release, and 45% migrated the next spring. The eel did not use the fish passes designed for upstream migration; thus, they were forced to go through the turbines, which resulted in 55% mortality. HEPs cause interruptions and delays in eel spawning migrations and are responsible for high eel mortality. This can make implementing an eel restitution plan difficult or even impossible in river systems with many barriers.

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.

Silvering of European eel (Anguilla anguilla L.): seasonal changes of morphological and metabolic parameters

2007 ◽  
Vol 57 (1) ◽  
pp. 63-77 ◽  
Author(s):  
S. Paul Balm ◽  
Caroline Durif ◽  
Vincent van Ginneken ◽  
Erik Antonissen ◽  
Ron Boot ◽  
...  
Keyword(s):  
Principal Component Analysis ◽  
Principal Component ◽  
Anguilla Anguilla ◽  
Component Analysis ◽  
Metabolic Energy ◽  
Hepatosomatic Index ◽  
European Eel ◽  
Silver Eel ◽  
Migratory Activity ◽  
Significant Difference

AbstractThe transformation of yellow eel into silver eel is called 'silvering', and takes place prior to migration. We found the sedentary yellow phase in spring, the migratory silver phase in autumn, while August was a cross-over month. We used principal component analysis (PCA) to characterise the morphological and physiological changes that accompany silvering in the European eel (Anguilla anguilla L.). Silvering is positively related to external parameters such as eye size, internal maturation parameters like GSI, vitellogenine (VIT), and blood-substrates such as phospholipids, Free Fatty Acids (FFA), and cholesterol. The Hepatosomatic Index was not significantly different between yellow and silver groups. In contrast, a significant difference was observed for parameters of body constitution (fat, protein, dry matter) between yellow and silver stages. Furthermore, the process of silvering is accompanied with increased levels of cortisol in autumn, which plays a role in mobilisation of metabolic energy from body stores towards migratory activity and gonadal growth. Based on Principal Component Analysis (PCA) with physiological, morphological and endocrinological parameters, it is concluded that during the process of silvering, several developmental stages can be recognised, with a timeframe of the premigratory sedentary yellow phase from April until July, August is a cross-over month, and the migratory silver phase is found from September until November.

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 Migration of silver eel, Anguilla anguilla , through three water pumping stations in The Netherlands

2020 ◽  
Vol 28 (1) ◽  
pp. 76-90
Author(s):  
Olvin Alior Keeken ◽  
Ralf Hal ◽  
Hendrik Volken Winter ◽  
Tony Wilkes ◽  
Arie Benjamin Griffioen
Keyword(s):  
The Netherlands ◽  
Anguilla Anguilla ◽  
Silver Eel ◽  
Water Pumping ◽  
Pumping Stations

Age and growth of the American eel (Anguilla rostrata (LeSueur)) in Newfoundland waters

1971 ◽  
Vol 49 (1) ◽  
pp. 121-128 ◽  
Author(s):  
R. W. Gray ◽  
C. W. Andrews
Keyword(s):  
Age Groups ◽  
Anguilla Anguilla ◽  
Age And Growth ◽  
Anguilla Rostrata ◽  
European Eel ◽  
Silver Eel ◽  
American Eel ◽  
Brackish Waters ◽  
American Eels ◽  
Freshwater Eels

The age (otolith readings) and growth of American eels (Anguilla rostrata (LeSueur)) from fresh and brackish waters in Newfoundland were studied. The eels in Burnt Berry Brook grew faster than eels in the other areas. The growth of young eels in brackish water was slow. Although the growth of these eels increased in subsequent age groups, freshwater eels were consistently larger at each age.The silver eel migrates after spending 12 to 13 years in Newfoundland waters. The American eel in Newfoundland is generally larger than the European eel (Anguilla anguilla L.) at the onset of migration; however, its appearance and state of maturity parallel the condition described in the European eel.

scholarly journals Model prediction vs. reality—testing the predictions of a European eel (Anguilla anguilla) stock dynamics model against the in situ observation of silver eel escapement in compliance with the European eel regulation

2013 ◽  
Vol 70 (2) ◽  
pp. 309-318 ◽  
Author(s):  
E. Prigge ◽  
L. Marohn ◽  
R. Oeberst ◽  
R. Hanel
Keyword(s):  
Model Prediction ◽  
Input Data ◽  
Anguilla Anguilla ◽  
In Situ Observation ◽  
European Eel ◽  
Dynamics Model ◽  
Silver Eel ◽  
Reality Testing ◽  
Model Predictions

Abstract Prigge, E., Marohn, L., Oeberst R., and Hanel, R. 2013. Model prediction vs. reality—testing the predictions of a European eel (Anguilla anguilla) stock dynamics model against the in situ observation of silver eel escapement in compliance with the European eel regulation – ICES Journal of Marine Science, 70: 309–318. A direct monitoring of European silver eel (Anguilla anguilla, L) escapement from rivers and estuaries has been proven to be challenging, and a Europe-wide documentation of escaping silver eel numbers therefore hardly seems realistic. To reinforce management decisions, policy-makers are thus widely reliant on the accuracy of escapement models. A 3-year programme of silver eel escapement monitoring was undertaken to compile model input data and revise an eel population model (German Eel Model II; GEM II) already used in the decision-making process of management authorities. By compiling necessary input data and analysing vital system-specific population characteristics, it was possible to compare the documented silver eel escapement with the modelled potential silver eel escapement. Resulting model predictions were close to actually monitored escapement numbers, which were distinctly lower than reference escapement values for the same freshwater system given in the implementation report of the German Eel Management Plans. Applying different commercial and recreational catch scenarios revealed the sensitivity of the model. The results show the potential of the GEM II and highlight the importance of high-quality input data to use model predictions as the basis for management measures.

scholarly journals Saving the European Eel: How Morphological Research Can Help in Effective Conservation Management

2020 ◽  
Vol 60 (2) ◽  
pp. 467-475
Author(s):  
Jens De Meyer ◽  
Pieterjan Verhelst ◽  
Dominique Adriaens
Keyword(s):  
Environmental Changes ◽  
Anguilla Anguilla ◽  
European Eel ◽  
Silver Eel ◽  
Critically Endangered Species ◽  
Morphological Studies ◽  
Management Measures ◽  
Migration Barriers ◽  
And Behavior ◽  
The Impact

Abstract The European eel (Anguilla anguilla) is a critically endangered species, whose recruitment stocks have declined to nearly 1% compared to the late 70s. An amalgam of factors is responsible for this, among them migration barriers, pollution, habitat loss, parasite infection, and overfishing. A lot of recent studies focus on aspects that can increase the mature silver eel escapement rate, such as identifying migration barriers and developing passageways or addressing the impact of pollution on the eel’s health. However, little attention is given to the eel’s morphology in function of management measures. Worryingly, less than 50% of the currently installed management plans reach their goals, strongly indicating that more information is needed about the eel’s ecology and behavior. Functional morphological studies provide insights on how species perform behaviors crucial for survival, such as feeding and locomotion, but also in how environmental changes can affect or limit such behaviors. Consequently, functional morphology represents an important biotic component that should be taken into account when making conservation decisions. Hence, here, we provide an overview of studies on the eel’s morphology that do not only demonstrate its relation with ecology and behavior, but also provide information for developing and installing proper and more specific management measures.

scholarly journals Mapping silver eel migration routes in the North Sea

2022 ◽  
Vol 12 (1) ◽  
Author(s):  
Pieterjan Verhelst ◽  
Jan Reubens ◽  
Johan Coeck ◽  
Tom Moens ◽  
Janek Simon ◽  
...  
Keyword(s):  
North Sea ◽  
Anguilla Anguilla ◽  
European Eel ◽  
English Channel ◽  
Migration Routes ◽  
Silver Eel ◽  
The North ◽  
Wide Range ◽  
Recent Developments ◽  
The North Sea

AbstractRecent developments in tracking technology resulted in the mapping of various marine spawning migration routes of the European eel (Anguilla anguilla). However, migration routes in the North Sea have rarely been studied, despite many large European rivers and hence potential eel growing habitat discharge into the North Sea. In this study, we present the most comprehensive map to date with migration routes by silver European eels in the North Sea and document for the first time successful eel migration through the English Channel. Migration tracks were reconstructed for 42 eels tagged in Belgium and 12 in Germany. Additionally, some eels moved up north to exit the North Sea over the British Isles, confirming the existence of two different routes, even for eels exiting from a single river catchment. Furthermore, we observed a wide range in migration speeds (6.8–45.2 km day−1). We hypothesize that these are likely attributed to water currents, with eels migrating through the English Channel being significantly faster than eels migrating northward.

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