Revolutionary Floating Elver Collector Design Components

The Elverator has been developed to safely, efficiently, and effectively collect migratory eels (elver) that encounter barriers as they swim upstream. It is 300% more effective than other collection methods. 


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About the elver.

Eel are catadromous fish that live in fresh water but spawn in the ocean. They migrate, often considerable distances, downstream to reach preferred salt water locations.  The eggs hatch and larvae drift with the ocean currents, growing and undergoing metamorphic changes to the “glass eel” stage.  When conditions are right, the nearly transparent glass eel enter freshwater rivers and estuaries and begin the long migrations upstream.  As they migrate, the elver gain in pigmentation and increase in size from 3 to 12 inches in length.

 Dams and other barriers have negatively impacted the distribution and population densities of eel in rivers and streams around the world. Eels play an integral role in the diverse ecosystems in which they reside. The three temperate eel species in the northern hemisphere, the European eel (Anguilla Anguilla), the American eel (Anguilla rostrate), and the Japanese eel (Anguilla japonica) are all endangered. The significant stock declines have led to restrictions on fishing and “the need to develop, investigate and improve technologies for upstream and downstream…eel passage at various barriers” (ASMFC 2013, SC DNR 2015)

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About The Elverator

Glass eels have been in dangerous decline for many years.

 Increased regulation to protect them has required new thought.   

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Many biologists and hydroelectric producers have found that traditional eel traps, often simple land-based ramp systems, have not been good enough to reverse the elver species decline, or to satisfy regulatory authorities in charge of their protection. 

The Elverator, the new Whooshh “Floating Elver Collector” is an effective new system that captures hundreds more elvers and can help to reverse the decline in eel populations.

Flow rate and climbing substrate are  influential features that directly impact the ability of elver to find and effectively climb. Typically, elver prefer the dark and generally are found to climb ramps at night. Bird and rodent predation of climbing elver can impact survival and collection success.


Elver behavior considerations were incorporated into the design components to increase elver attraction and facilitate ease of passage from the waterway into the collector. 

The Elver Floating Collector is a turnkey solution to address elver upstream migration challenges at dams and other obstacles. We integrated the needs and preferences of the elver via the use of a floating device which also addresses river level fluctuations issues, predation and disease transmission concerns, and attraction flow challenges.  The installation of a single Elver Floating Collector was 1.5 times more effective at collecting elver than three land-based elver traps combined. 

In addition, a single Elver Floating Collector positioned on the River Göta älv in the summer of 2018, at the Lilla Edet hydropower station in Sweden, demonstrated benefits in efficiency both in elver collection and productive trap management compared to the three land-based elver traps. Each trap or collector requires fish management (O&M, operation and management) support to empty and transport the elver from the trap. Whether a trap contains a small number or a large number of elver, the O&M effort required to service the trap is similar. To reduce overhead via reduced O&M effort afforded by supporting a single elver floating collector installation, as opposed to three land-based traps, is a tangible economic and operational benefit.

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