Although widely in use throughout Europe and the U.K. for some time now, the Screw is a newcomer in North America.
On the basis of previous studies carried out in Europe which
supported the claims to fish-friendliness, the first Ontario Screw
installation was installed in 2013.
Literally thousands of fish passages have been monitored and recorded
using underwater cameras at the intake, inside the chamber of the Screw
itself and at the outflow to assess the effect of the Screw on
salmonids (including smolts and kelts), brown trout and eels. The trials
looked at fish passage across a broad spectrum of sizes and turbine
speeds, possibly the most impressive of which was the safe passage of a
kelt measuring 98cm in length and weighing 7.6kg.
The European studies conclude that the Archimedean Screw turbine is
indeed fish- friendly with no adverse physical effect on fully grown
fish or kelts; at most 1.4% of smolts sustaining limited and recoverable
scale loss (NB ‘at most’ because these were wild fish and quite likely
to have sustained some scale damage prior to entry into the turbine) and
just 1 out of 160 eels (0.64%) suffered minor and recoverable pinching
to the tail. In addition, behavioural and migrational patterns across
the species have been shown to be entirely unaffected by the turbine.