Install fish elevators/lifts

Supporting evidence from individual studies

1. A study (year not stated) in a river in Dordogne, France (Legault 1992) reported that a fish elevator at a hydropower dam was used by fewer, larger eels compared to sloped ramps with bristles. Over 12 days, 202 eels were caught using a fish elevator compared to 6,276 eels using ramps. Eels using the fish elevator were significantly larger (average 293 mm) than eels using the ramps (average 223 mm). During 12 days in June–July, eels were trapped after passing through a fish elevator and over three experimental ramps (consisting of brushes mounted on PVC supports, each 2.4 m long and 0.3 m wide). The slope of the ramps was modified every 3–4 days. Measurements were taken for all 202 eels that used the fish elevator and 3,454 eels that used the ramps. 

   Study and other actions tested

   Referenced paper

   Legault A. (1992) Etude de quelques facteurs de sélectivité de passes à anguilles. Bulletin Français de la Pêche et de la Pisciculture, 83-91.

2. A study in 1998–1999 in a river in Viana do Castelo District, Portugal (Santos et al. 2002) found that a fish lift at a dam was used by some European eels Anguilla anguilla to travel upstream, and a similar number used it during the day and night. Over a 12-month period, the fish lift was used by eels from May to October (total 121 eels). Most eels used the lift in July (102 eels). The average number of eels using the lift each time it was lifted did not differ significantly during the day (0.01–1.2 eels/lift/month) or night (0.02–0.5 eels/lift/month). The fish lift was built for upstream migration past a dam built in 1992. Three entrances in a channel within the tailrace of a powerhouse led to a cage in the fish lift. Two automatic video cameras, one on top and one outside of the lift, were used to monitor the fish lift for a 12-month period from March 1998–February 1999. The cage was lifted in 4-h cycles and an image captured once every cycle. 
   

   Study and other actions tested

   Referenced paper

   Santos J.M., Ferreira M.T., Godinho F.N. & Bochechas J. (2002) Performance of fish lift recently built at the Touvedo Dam on the Lima River, Portugal. Journal of Applied Ichthyology, 18, 118-123.

3. A study in 1995–2002 in a river in northern Brittany, France (Laffaille et al. 2005) found that, 10 years after installing a fish lift at a dam, along with eel passes in three other dams, European eel Anguilla anguilla density, biomass and length declined in river sections furthest upstream of the lift, but did not change in all other upstream and downstream sections along the river. During 3–10 years after installation of a fish lift and eel passes, average eel density did not change significantly in each of two river sections downstream of the lift (year 3: 0.1 eels/m2, year 10: 0.1–0.2 eels/m2) or five of six river sections upstream of the lift (year 3: 0.1–0.4 eels/m2, year 10: 0.1–0.7 eels/m2).  In the other section, located furthest upstream, average eel density declined (year 3: 0.4 eels/m2, year 10: 0.1 eels/m2). Over the same period, average eel biomass and length declined in two river sections upstream of the lift, but did not change significantly in the four other sections upstream or two sections downstream (see paper for data). In 1992, a fish lift was installed in a 14-m high impassable dam in the river Frémur. In 1996, eel passes (details not provided) were installed in two 4–6-m high, partially impassable dams (previously only eels <120 mm could pass) downstream of the fish lift. Each September from 1995–2002, eels were captured by electric fishing (net mesh size 3mm) in eight river sections (each 430–1,500 m2), 4–17 km upstream of the estuary (two sections downstream and four upstream of the fish lift). In total, 7,079 eels were weighed, measured and released. 

   Study and other actions tested

   Referenced paper

   Laffaille P., Acou A., Guillouët J. & Legault A. (2005) Temporal changes in European eel, Anguilla anguilla, stocks in a small catchment after installation of fish passes. Fisheries Management and Ecology, 12, 123-129.