scholarly journals Flow-wise or path-wise: diffusion in a fragmented dendritic network and implications for eels

2018 ◽  
Author(s):  
J. Domange ◽  
P. Lambert ◽  
L. Beaulaton ◽  
H. Drouineau
Keyword(s):  
Time Series ◽  
Anguilla Anguilla ◽  
River Networks ◽  
European Eel ◽  
River Catchment ◽  
Dendritic Network ◽  
Long Time ◽  
Colonization Process ◽  
River Fragmentation ◽  
River Catchments

AbstractThe European eel (Anguilla anguilla) is a catadromous species that reproduces at sea and inhabits continental waters during its growth phase. River fragmentation due to obstacles is considered one cause of the decline of this species. However, the colonization process of river catchments by eels is still poorly understood. In this article, we compare two scenarios for the diffusion of eels within river catchments: a path-wise scenario, in which movements are totally random, and a flow-wise scenario, in which movements are partially oriented. Based on these two scenarios, we attempted to predict the distribution of eels within dendritic river catchments, explicitly accounting for the presence of obstacles to movement. The model was fitted to a long-time series of electro-fishing data. The results suggest that the path-wise scenario is more predominant than the flow-wise scenario. Moreover, results show that the distribution of eels in river catchment depends on (i) the types of movements carried out by eels, (ii) the configuration of river networks and (iii) the positions of obstacles within catchments.

scholarly journals Response of seaward-migrating European eel ( Anguilla anguilla ) to manipulated flow fields

2015 ◽  
Vol 282 (1811) ◽  
pp. 20151098 ◽  
Author(s):  
Adam T. Piper ◽  
Costantino Manes ◽  
Fabio Siniscalchi ◽  
Andrea Marion ◽  
Rosalind M. Wright ◽  
...  
Keyword(s):  
Anguilla Anguilla ◽  
High Water ◽  
Fish Passage ◽  
Physical Contact ◽  
Mitigation Measures ◽  
River Networks ◽  
European Eel ◽  
Search Behaviour ◽  
Velocity Gradients ◽  
Poor Understanding

Anthropogenic structures (e.g. weirs and dams) fragment river networks and restrict the movement of migratory fish. Poor understanding of behavioural response to hydrodynamic cues at structures currently limits the development of effective barrier mitigation measures. This study aimed to assess the effect of flow constriction and associated flow patterns on eel behaviour during downstream migration. In a field experiment, we tracked the movements of 40 tagged adult European eels ( Anguilla anguilla ) through the forebay of a redundant hydropower intake under two manipulated hydrodynamic treatments. Interrogation of fish trajectories in relation to measured and modelled water velocities provided new insights into behaviour, fundamental for developing passage technologies for this endangered species. Eels rarely followed direct routes through the site. Initially, fish aligned with streamlines near the channel banks and approached the intake semi-passively. A switch to more energetically costly avoidance behaviours occurred on encountering constricted flow, prior to physical contact with structures. Under high water velocity gradients, fish then tended to escape rapidly back upstream, whereas exploratory ‘search’ behaviour was common when acceleration was low. This study highlights the importance of hydrodynamics in informing eel behaviour. This offers potential to develop behavioural guidance, improve fish passage solutions and enhance traditional physical screening.

scholarly journals Environmental DNA metabarcoding provides enhanced detection of the European eel Anguilla anguilla and fish community structure in pumped river catchments

2020 ◽  
Vol 97 (5) ◽  
pp. 1375-1384 ◽  
Author(s):  
Nathan P. Griffiths ◽  
Jonathan D. Bolland ◽  
Rosalind M. Wright ◽  
Leona A. Murphy ◽  
Robert K. Donnelly ◽  
...  
Keyword(s):  
Community Structure ◽  
Fish Community ◽  
Anguilla Anguilla ◽  
Environmental Dna ◽  
European Eel ◽  
Fish Community Structure ◽  
Dna Metabarcoding ◽  
River Catchments

Behavioural syndrome in juvenile eels and its ecological implications

Behaviour ◽  
2015 ◽  
Vol 152 (2) ◽  
pp. 147-166 ◽  
Author(s):  
Benjamin Geffroy ◽  
Bastien Sadoul ◽  
Agnès Bardonnet
Keyword(s):  
Life History ◽  
Anguilla Anguilla ◽  
Population Level ◽  
Behavioural Syndrome ◽  
European Eel ◽  
Diurnal Activity ◽  
Nocturnal Activity ◽  
Time Period ◽  
Ecological Implications ◽  
Long Time

Behavioural syndrome, which refers to a suite of correlated behaviours across differing situations, has been identified in numerous animals, including fish. The presence and conservation of a behavioural syndrome throughout evolutionary times suggests it confers various advantages at a population level. In eels, such as the European eel (Anguilla anguilla), activity and aggressiveness are important factors in their life history, since both traits influence dispersal and territoriality. In the present study we investigated whether these behavioural traits were consistent at both the nychtemeral scale (24 h) and over a long time period (7 months). In addition, we investigated if aggressiveness and activity were positively correlated. Both activity and aggressiveness were significantly repeatable, indicating that both behavioural traits could be considered as personality traits. Interestingly, nocturnal activity was correlated to diurnal activity, indicating that this personality trait was highly stable at the circadian scale. Both aggressiveness and activity were correlated in the course of the experiment, underlining the presence of a behavioural syndrome. The detection of two behaviourally distinct groups in juvenile eels: aggressive and active individuals versus their counterpart have implications in the understanding of the colonization profile of the watershed. We discuss these findings in relation to the ecology of this species.

scholarly journals The decline in recruitment of the European eel: new insights from a 40-year-long time-series in the Minho estuary (Portugal)

2018 ◽  
Vol 75 (6) ◽  
pp. 1975-1983 ◽  
Author(s):  
Maria João Correia ◽  
José Lino Costa ◽  
Carlos Antunes ◽  
Giulio De Leo ◽  
Isabel Domingos
Keyword(s):  
Time Series ◽  
European Eel ◽  
Long Time Series ◽  
Long Time ◽  
Minho Estuary

scholarly journals Long-term variation in numbers and biomass of silver eels being produced in two European river systems

2018 ◽  
Vol 75 (5) ◽  
pp. 1627-1637 ◽  
Author(s):  
W Russell Poole ◽  
Ola H Diserud ◽  
Eva B Thorstad ◽  
Caroline M Durif ◽  
Conor Dolan ◽  
...  
Keyword(s):  
Time Series ◽  
Life Stage ◽  
Early Period ◽  
Anguilla Anguilla ◽  
High Water ◽  
Water Levels ◽  
Annual Number ◽  
European Eel ◽  
Silver Eel ◽  
Silver Eels

Abstract The European eel (Anguilla anguilla) population has been in decline at least since the 1960s and reliable regional information, particularly on the spawner production and escapement (i.e. the silver eel life stage), is a requirement of the EU stock recovery regulation. Two comparable time series exist in Burrishoole (Ireland) and Imsa (Norway), with monitoring of total silver eel production since the early 1970s. Numbers of emigrating silver eels fell significantly (p < 0.0001) in the 1980s (breakpoints: Burrishoole 1982; Imsa 1988), in both catchments from >4000 eels per annum to ∼2000 eels per annum. The proportion of male eels dropped and the average size of female eels increased. Biomass of silver eels escaping has remained similar in Burrishoole (1.1/1.2 kg/ha), but not in Imsa (2.1/0.9 kg/ha) between the early period and the 2000s. Factors that govern the onset of eel maturation (silvering) and the annual production of silver eels are little understood. In this paper, the influence of time-lagged environmental variables on silver eel production is examined. Annual variation in the time series was partly (r2 Burrishoole = 0.43, Imsa = 0.46) explained by variation in water temperature and water level. Annual number of migrating eels in both catchments was positively related to summer temperature and summer water flow, negatively related to summer temperatures in the previous year, and in the Burrishoole, also negatively related to high water levels in September/October. The models did not transfer well between catchments, indicating likely catchment specific environmental factors impacting on eel production. The reduction in eel numbers observed in both catchments, accompanied by the change in sex ratio and mean weight of females that contribute to maintain biomass production, calls into question the advisability of basing a spawner escapement recovery target on biomass alone, while numbers and proportions of males decline.

Metazoan Parasites and Health State of European Eel, Anguilla Anguilla (Anguilliformes, Anguillidae), From Tonga Lake and El Mellah Lagoon in the Northeast of Algeria

2018 ◽  
Vol 52 (4) ◽  
pp. 279-288 ◽  
Author(s):  
F. Bakaria ◽  
S. Belhaoues ◽  
N. Djebbari ◽  
M. Tahri ◽  
I. Ladjama ◽  
...  
Keyword(s):  
Brackish Water ◽  
Parasite Species ◽  
Anguilla Anguilla ◽  
European Eel ◽  
Health State ◽  
Component Community ◽  
Metazoan Parasites ◽  
Parasite Communities ◽  
High Dominance ◽  
Argulus Foliaceus

Abstract The aim of the study was to examine metazoans parasite communities of European eels (Anguilla anguilla) in freshwater (Tonga Lake) and brackish water (El Mellah lagoon) in the northeast of Algeria. Six parasite taxa were collected: one monogenean, Pseudodactylogyrus sp.; two crustaceans, Ergasilus sp. and Argulus foliaceus; two nematodes, Cucullanus sp. and Anguillicola crassus; one cestode, Bothriocephalus claviceps. Th e most prevalent parasite taxa in freshwater were Pseudodactylogyrus sp., A. crassus and Bothriocephalus claviceps; whereas in the brackish water, eels were infected mainly with A. crassus. Th e characteristics of the parasite component community structure revealed low parasite species diversity and high dominance values in eels from the two localities. Both communities were dominated by a single parasite species: Tonga eels by the monogenean Pseudodactylogyrus sp. and El Mellah lagoon eels by the nematode A. crassus, verified by high Berger-Parker dominance values of 0.76 and 0.87 respectively.

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