Tests prove fish-friendly credentials

Comprehensive, detailed studies into Archimedean Screw hydropower turbines conducted at the River Dart Country Park at Ashburton in Devon have confirmed its fish-friendly credentials. The Screw, installed by Mann Power, was conducted in conjunction with the Environment Agency who agreed to monitor the turbine over the course of a year.

On the basis of previous studies carried out in Europe which supported the claims to fish-friendliness, the Environment Agency permitted the first UK Screw installation (on the River Dart at Ashburton in Devon) to run unscreened for a year whilst monitoring was taking place. During that time, marine biologist Pete Kibel of Fishtek Ltd – in consultation with the Environment Agency and members of the Fish Pass Panel – has undertaken our comprehensive live fish trials at the site and the extremely positive results are now informing national policy on micro-hydro.

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 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.

At a time when the national media seems determined to demonise micro-hydro developers as “anti-conservationist”, quoting anecdotal evidence of ’damage to fish stocks’, it is always good to know that we have science on our side.

If you would further information about Fishtek, you can visit their website here.