| 1. |
- Calles, Olle, 1974-, et al.
(författare)
-
Efficient and timely downstream passage solutions for European silver eels at hydropower dams
- 2021
-
Ingår i: Ecological Engineering. - : Elsevier. - 0925-8574 .- 1872-6992. ; 170
-
Tidskriftsartikel (refereegranskat)abstract
- The European eel population is critically endangered due to a multitude of human-induced factors such as habitat fragmentation, parasites, fishing, and climate change. In freshwater, downstream migrating silver eels encountering hydroelectric plants often suffer substantial delays and increased mortality from trash-rack impingement and turbine-induced mortality. Downstream passage problems can be ameliorated by implementing different types of downstream passage solutions that show variable but promising results for salmonids, but their performance for silver eels remains largely unknown. To address these knowledge gaps, radio telemetry was used to monitor the downstream migration of silver eels during 2 years past a hydroelectric plant recently equipped with two new fish passage solutions, consisting of an angled bar rack with a full-depth bypass, and a nature-like fishway. No tagged eels passed through the turbines, but bypassed the dam evenly between the two passage solutions, resulting in a 95% impediment passage efficiency and a median passage time of 1 h. Movement patterns and route selection were associated with variation in discharge and most individuals approached both passage solutions before passing, resulting in route-specific efficiencies of 69% for the angled rack and bypass, and 46% for the nature-like fishway. We conclude that the combination of a new bypass, paired with an angled rack, and a large nature-like fishway provided downstream migrating silver eels with a highly effective combination of passage solutions, with high impediment passage success and relatively low passage times.
|
|
| 2. |
- Nilsson, Per Anders, 1968-, et al.
(författare)
-
Substrate-size choice in European eel (Anguilla anguilla) elvers is not altered by piscivore chemical cues
- 2020
-
Ingår i: Journal of Fish Biology. - : John Wiley & Sons. - 0022-1112 .- 1095-8649. ; 96:6, s. 1534-1537
-
Tidskriftsartikel (refereegranskat)abstract
- The European eel Anguilla anguilla Linnaeus 1758 is critically endangered with recruitment estimated at 5-10% of historical levels. Enhancing survival of recruits is pivotal for conservation, and restoration should consider habitat choice of elvers ascending river systems. We experimentally show that newly ascended elvers choose small pebble habitat over finer and larger substrates, regardless of the presence or absence of piscivore chemical cues, indicating no predator-induced change in substrate choice. Enriching habitats with this substrate fraction should enhance eel recruitment as well as biodiversity at large.
|
|
| 3. |
- Watz, Johan, 1977-, et al.
(författare)
-
Evaluation of a novel mobile floating trap for collecting migrating juvenile eels, Anguilla anguilla, in rivers
- 2017
-
Ingår i: Fisheries Management and Ecology. - : John Wiley & Sons. - 0969-997X .- 1365-2400. ; 24:6, s. 512-514
-
Tidskriftsartikel (refereegranskat)abstract
- To improve the situation for the threatened European eel in regulated rivers, better methods need to be developed that more efficiently collect and transport juvenile eels past dams. In this study, a novel mobile, floating eel trap is described, and the results from an evaluation of the trap in two Swedish regulated rivers are presented. The mobile trap was designed to reduce the length of the climbing distance while maximizing the width of the entrance. The mobile trap caught more juvenile eels than a stationary eel ladder, serving as control. Furthermore, the mobility of the floating trap enables adaptive placement and thus offers managers the possibility to search for the spatial optimum for trapping efficiency.
|
|
