Effect of re-opening of a migratory pathway for eel (Anguilla anguilla, L.) at a watershed scale

Published source details Briand C., Fatin D., Fontenelle G. & Feunteun E. (2005) Effect of re-opening of a migratory pathway for eel (Anguilla anguilla, L.) at a watershed scale. Bulletin Français de la Pêche et de la Pisciculture, 67-86.
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This study is summarised as evidence for the following.

	Action	Category
	Install climbing structures for fish Action Link

Install climbing structures for fish

A before-and-after study in 1981 and 1996–2003 in a river in Brittany, France (Briand et al. 2005) found that some glass and yellow European eels Anguilla anguilla used an eel ladder at a tidal dam to travel upstream, and eel densities increased in upstream areas after the ladder was installed. Each year from 1996 to 2003, approximately 0.2–2.5 million glass and 6,600–37,000 yellow eels were captured on the eel ladder. On average, eel densities were greater upstream of the dam during six years after installation of the ladder (0.3–0.8 eels/m2) compared to one year before (0.1 eels/m2). In 1995, an eel ladder (comprising two inclined panels with synthetic bristles located on each side of a pooling pass) was installed on a tidal dam within an estuary. The dam was constructed in 1970 to reduce flooding. Thirteen additional eel ladders were constructed on dams further inland (>100 km from the sea) in 1999 and 2000 (use by eels not reported). Electrofishing surveys were carried out in netted sections (120–1,200 m2) in 10 tributaries of the river system before (1981 in 17 sections) and after (1998–2003 in 19 sections) installation of the eel ladder on the tidal dam. In 1996–2003, eels were captured in nets on the ladder daily during spring and weekly when catches were low. Yellow eels were counted and glass eel numbers estimated from wet weight.

(Summarised by: Anna Berthinussen)