Downstream passage and impact of turbine shutdowns on survival of silver American eels at five hydroelectric dams on the Shenandoah River

Published source details Eyler S.M., Welsh S.A., Smith D.R. & Rockey M.M. (2016) Downstream passage and impact of turbine shutdowns on survival of silver American eels at five hydroelectric dams on the Shenandoah River. Transactions of the American Fisheries Society, 145, 964-976.
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This study is summarised as evidence for the following.

	Action	Category
	Modify operation of underwater turbines Action Link

Modify operation of underwater turbines

A replicated, controlled study in 2007–2010 at five hydropower stations along a river in Virginia and West Virginia, USA (Eyler et al. 2016) reported that shutting down turbines at night led to reduced mortality rates of migrating American eels Anguilla rostrata. Overall mortality rates of American eels migrating downstream past dams at five power stations were lower during periods when turbines were shutdown (0–7%) than during normal turbine operations (6–38%), although Results are not based on tests of statistical significance. Similar numbers of eels passed dams while turbines were shutdown (17–35 eels/dam) and during normal operations (16–52 eels/dam). From 15 September to 15 December 2007–2010, turbines at five hydropower stations (3–4 turbines/station) were shut down from 18:00 to 06:00 h and all water diverted to the dam spillway. Normal operations were resumed at all other times. In September–December 2007–2009, a total of 145 eels (average length 85 cm) were captured by electrofishing in the Shenandoah River upstream of each hydropower station. Captured eels were fitted with radio tags and released. Tagged eels were tracked passing each dam from September 2007 to August 2010. 

(Summarised by: Anna Berthinussen)