Eel Passage

Eel Passage Design

Upstream eel passage facilities, often called eel ladders, are fairly different from other types of fishways. Eels are catadromous fish meaning that the juveniles (elvers) migrate up river to their habitat and pass many years in freshwater until they reach their adult size. Once they have reached their adult size, they migrate downstream to the sea to spawn. 

At their juvenile stage, eels can slither out of the water to pass obstacles even if there is only a minimal amount of water (i.e. even on wet grass elvers can migrate upstream). A typical eel ladder consists of a shallow channel most often composed of aluminum or wood with an artificial climbing substrate installed at the bottom. The climbing substrate may be composed of bristles, PVC tubes, geotextile (enkamat or akwadrain), or proprietary eel specific materials (Milieu, Inc. or Fish-Pass). A minimal amount of water is used to keep the substrate wet and allow eels to climb this type of fishway. 

Due to their length when passing downstream as adults it is particularly important to prevent turbine entrainment and provide a bypass route to allow eels to pass safely around hydro facilities. Similar to standard fishways, eel passage considerations include biological, hydraulic, structural and existing facility criteria. 



Fish Passage Projects