Facilitating Elver Migration Jonas.elghagen@whooshh.com
C onventional Elver Ladders
No major design changes have been applied to improve standard ladders over historical approaches
Elvers & fish ladders? Mean burst capacity of elver ≤0.5 m/s Traditional fish ladders: Baffle, Pool and Weir etc. are not suitable for efficientelver passage. “Engineering does not regard fish ladders as a primary method of passing eels.” USFWS 2017
Improving Elver Collection Efficiency through Innovation: How? • Addressing shortfalls of the conventional approaches • Considering elver behavior • Considering trap durability, function and performance
Elverator™ The floating elver collector
The Elverator ™ Advantages • Floating mobility accomodates elver preferences, not dictated by local conditions • River fluctuations do not impact the trap’s attraction flow or elver climbing distance • Wider and shorter ramps provide climb savings: time and energy • Designed to exclude predation from mammals, birds and fish • Attraction flow optimized to attract, guide and collect • Trap is easily moved to alternative sites and lifted out of the water during the off-season
Elverator™ Advantages The trap itself creates a 9,5 m². shadowed area Two Ramps, dimensions up to: 2,8 m wide, 1 m long Conventional designs: 0,4m wide, up to 30-40m long Tarp, steel panel and stainless-steel net protect elvers from predation
Elverator™ Function Elvers climb up ramps hoses leads elvers to submerged Pipes provide Pipes provide water to the climbing substrate primary collection box (hoses not in pic) attraction flow and the initial collection channel.
Climbing substrate EF:16 ™ • Egg carton structure designed as a interfitting tile system • Used in floating elver trap tests performed in 2016, 2018 & 2019
Studies & Results
2019 Karlstads University Elver climbing substrate study Climbing the ladder: an evaluation of three different anguillid eel climbing substrata and placement of upstream passage solutions at migration barriers Watz et al. 2019
Watz et al. 2019 Elver climbing substrate study • EF:16 ™ 40% 21% • Enkamat • Bristle substrate 5% Eels using the EF: 16 ™ substrate climbed 26% faster than those using the bristle substrate and almost four times as fast as those climbing in the Enkamat.
Results: River Lagan 2016 Pilot testing the Elverator ™
2016: River Lagan The Elverator ™ vs. Convential elver ladder River Lagan studies designed to maintain variables: • Attraction flow • Amount of water on climbing substrate • Ramp angle Tests performed by Karlstads University Evaluation of a novel mobile floating trap for collecting migrating juvenile eels, Anguilla anguilla , in rivers Watz et al. 2017
River Lagan night time test: 08:00 pm – 08:00 am for 10 nights Watz et al. 2017
Results: River Göta älv 2018,2019
River Göta älv, 2018 & 2019 2018 Evaluations : • Collection efficiency at three different locations • Collected elver size distribution 2019 Evaluations : • New attraction flow signature • Proof of Concept Elver Chamber™
Elverator™ outperforms collection efficiency of conventional pipe traps regardless of location 100% 100% 100% 80% 80% 80% 65% 64% 57% 60% 60% 60% 40% 40% 40% 24% 23% 20% 16% 12% 20% 20% 20% 10% 7% 0% 0% 0% 0% 0% Trap 1. Trap 2. Trap 3. Elverator ™ Trap 1. Trap 2. Trap 3. Elverator ™ Trap 1. Trap 2. Trap 3. Elverator ™ Elverator™ at Pos. 1: Elverator™ at Pos. 2: Elverator™ at Pos. 3: Percentage of average catch/day Percentage of average catch/day Percentage of average catch/day
The Elverator™ supports collection of a greater size range (3-12+ inches) Conventional Pipe trap 1. Conventional Pipe trap 2. Conventional Pipe trap 3. The Elverator ™ 1,5% 7,8% 90,7% Distribution of collected 6-12 inch (large) elver
Results: River Göta älv 2019 Testing New attraction flow signature
Catch distribution, Test cycle 1. Lilla Edet 2019 Testing new attraction flow signature 90% 78% 80% 73% 73% 71% 66% 70% 60% 50% 40% 30% 20% 10% 0% 20-July 22-July 26-July 30-July 01-aug Elverator™ conventional pipe elver ladder 1. conventional pipe elver ladder 2. conventional pipe elver ladder 3.
New attraction flow signature increased Elverator™ collection efficiency 700 600 500 400 300 200 100 0 20-july 21-july 22-july 25-july 26-july 27-july 30-july 31-july 01-aug 02-aug New attraction flow signature Standard attraction flow
Emptying the trap options • 2018 study : Trap accessed using hoist Elvers collected in separate collection box • 2016 study : Trap accessed by boat Elvers collected in mesh bag • 2019 study : Elvers collected in mesh bag Emptying using block & tackle
The Elver Chamber ™ Automatic transport of trapped elver ”Emptying the Elverator ™ or Switchback ™”
Proof of Concept: Elver Chamber™ • Pump: 85 GPM • Pump time: On for 30 sec • 4 m transported height (13 ft.) • 8 m transported length (26 ft.) Transport evaluation: Subset held 8 days for observation • 10 elvers, Elverator™ transported via the Elver Chamber ™ • 10 elvers, from conventional pipe trap (control) Transport Successful: No negative impact All elver, transported and controls, were alive, healthy, active, and unharmed. After 8 days they were released back to the river.
Switchback™
Switchback™ • Modular • Variable height – just add sections (92cm per section) • Minimal land footprint = increased positioning options • Vertical guide rail mounted for easy end-of-season take out • Predation screening • Dimensions: 830 x 980 mm x height*
Thank you for listening Stay Safe! & look after your elders Jonas.elghagen@whooshh.com
Extra slides
Existing trap 1. Pos. 1 Existing trap 2. Pos. 2 Lilla Edet hydro power station Göta älv, Sweden Pos. 3 Existing trap 3.
Blocking elvers from reaching their “habitat of choice” A.Increased competition between individuals = lower survival B. Increased predation = lower survival C.Possible modification to the sex ratio, as sex determination appears to be density-dependent Geffroy et. al 2015 => Blocked or poorly accessed habitats impact survival and the sex-ratio.
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