Facilitating Elver Migration Jonas.elghagen@whooshh.com C - - PowerPoint PPT Presentation

Facilitating Elver Migration

Jonas.elghagen@whooshh.com

Conventional Elver Ladders

No major design changes have been applied to improve standard ladders over historical approaches

“Engineering does not regard fish ladders as a primary method of passing eels.”

USFWS 2017

Mean burst capacity of elver ≤0.5 m/s Traditional fish ladders: Baffle, Pool and Weir etc. are not suitable for efficientelver passage.

Elvers & fish ladders?

Improving Elver Collection Efficiency through Innovation:

• Addressing shortfalls of the conventional approaches
• Considering elver behavior
• Considering trap durability, function and performance

How?

Elverator™

The floating elver collector

• 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

The Elverator™

Advantages

Elverator™

Two Ramps, dimensions up to: 2,8 m wide, 1 m long

Conventional designs: 0,4m wide, up to 30-40m long

The trap itself creates a 9,5 m². shadowed area Tarp, steel panel and stainless-steel net protect elvers from predation

Advantages

Elvers climb up ramps

Elverator™ Function

Pipes provide water to the climbing substrate and the initial collection channel. Pipes provide attraction flow hoses leads elvers to submerged primary collection box (hoses not in pic)

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

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.

Watz et al. 2019

Elver climbing substrate study

• EF:16 ™
• Enkamat
• Bristle substrate

40% 21% 5%

Results: River Lagan 2016

Pilot testing the Elverator™

2016: River Lagan

The Elverator™ vs. Convential elver ladder

Evaluation of a novel mobile floating trap for collecting migrating juvenile eels, Anguilla anguilla, in rivers Watz et al. 2017

Tests performed by Karlstads University

River Lagan studies designed to maintain variables:

• Attraction flow
• Amount of water on climbing substrate
• Ramp angle

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™

10% 24% 0%

64%

0% 20% 40% 60% 80% 100% Trap 1. Trap 2. Trap 3. Elverator ™ 16% 20% 7%

57%

0% 20% 40% 60% 80% 100% Trap 1. Trap 2. Trap 3. Elverator ™ 23% 12% 0%

65%

0% 20% 40% 60% 80% 100% Trap 1. Trap 2. Trap 3. Elverator ™

Elverator™ at Pos. 1: Percentage of average catch/day Elverator™ at Pos. 3: Percentage of average catch/day Elverator™ at Pos. 2: Percentage of average catch/day

Elverator™ outperforms collection efficiency of conventional pipe traps regardless of location

Distribution of collected 6-12 inch (large) elver

The Elverator™ supports collection of a greater size range

(3-12+ inches)

7,8% 1,5%

90,7%

Conventional Pipe trap 1. Conventional Pipe trap 2. Conventional Pipe trap 3. The Elverator ™

Results: River Göta älv 2019

Testing New attraction flow signature

73% 73% 71% 66% 78%

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 20-July 22-July 26-July 30-July 01-aug conventional pipe elver ladder 1. conventional pipe elver ladder 2. conventional pipe elver ladder 3.

Elverator™

Catch distribution, Test cycle 1. Lilla Edet 2019

Testing new attraction flow signature

100 200 300 400 500 600 700 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

New attraction flow signature increased Elverator™ collection efficiency

Emptying the trap

• 2016 study: Trap accessed by boat

Elvers collected in mesh bag

• 2018 study: Trap accessed using hoist

Elvers collected in separate collection box

• 2019 study: Elvers collected in mesh bag

Emptying using block & tackle

• ptions

Automatic transport of trapped elver ”Emptying the Elverator™ or Switchback™”

The Elver Chamber™

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™

• 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*

Switchback™

Thank you for listening

Jonas.elghagen@whooshh.com

Stay Safe! & look after your elders

Extra slides

• Pos. 2
• Pos. 1
• Pos. 3

Existing trap 2. Existing trap 1. Existing trap 3.

Lilla Edet hydro power station Göta älv, Sweden

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.