The Elver
Our Impact
The Evidence
The Elver

what are 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. They are an important part of the nutrition cycle, offering a significant food source for fish, mammals, birds, and turtles - as well as regulating the population of other animals.  

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)

what do we do?

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. Glass eels have been in dangerous decline for many years, and increased regulation to protect them has required new thought. 

Our systems were designed 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 Elverator, the new Whooshh “Floating Elver Collector” is an effective new system that captures three to five times more elver and can help to reverse the decline in eel populations.

Our Impact

what is our impact?

Our autonomous elver passage designs are based on eel behavior and were perfected in Sweden. The Elverator not only protects elver from predators, but independent studies have confirmed this unique floating system safely collects 300% more elver, including larger elver, than traditional systems often in place today. 

The ability to passage larger elver is a component we prioritize, as the larger elver are more often the females, and without them reproduction rates among elver will continue to stagnate. 

The Whooshh Innovations EF-16 Climbing Substrate, a crucial part in our systems, is a durable and modular substrate that has not just been designed to be attractive to eels. It’s distinct advantage is that it has been designed to attract and pass a broad cross-section of eels, from elver to yearlings, with a wide range of sizes, specifically accommodating the larger females. Assisting more eels on their migratory journey helps restore populations more quickly – a critical need for many eel species.

The Evidence

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. 



or, just the elver systems.