Sorn Castle Dam- New Fish Pass installed by Ayrshire Rivers Trust

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Sorn Castle Dam as ART commenced work

Sorn Castle Dam has long been a concern for salmonid migration having an incomplete Larinier fish pass that was virtually impossible for fish to use. There were no ideal alternatives for lower flow conditions leaving fish struggling to get over if they missed the optimal flow levels. The fish pass was in the process if construction back around 2007  when the contractors went into liquidation leaving the job half done and a problem to migrating fish for years to come. It required considerable work to complete and the cost for this was expected to be high.

The incomplete and ineffective Larinier fish pass that existed

Yes salmon made it over the Castle Weir in high water but often fish were seen lying on their side and exhausted, particularly as spates subsided. Salmon were also forced to seek a route over through shallow water with their tails exposed or resting in pockets of water as they recovered from their efforts to get over. These issues were not something that missed the attention of those willing to take salmon illegally and over the years, considerable numbers of fish have been poached at this dam. For years this problem has been an issue raised at the River Ayr DSFB AGM.

Two weeks ago, Ayrshire Rivers Trust managed to agree a way forwards with the estate factor and SEPA and ordered the timber hoping to beat any rain. Thankfully they did and with the work now complete, the heavens can open and allow the fish up and ART staff an opportunity to assess the effectiveness of this work.

ART staff constructing the new timber baffle and baulk fish pass

ART staff spent the last 4 days designing and building a timber baffle & baulk fish pass to the left side of the dam face where most fish seemed to attempt to get over. They have installed untreated Red and English Oak baffles, the best and most enduring timbers for use in water. Two larch baulks were added to the face to capture water and create an attraction flow that should allow the fish over the last and steepest slope to the crest. They also removed some 30 tonnes of sediment built up behind the dam and used this to fill holes where fish often became trapped and poached. Some of this material will be redistributed downstream in spates and that is an essential part of managing sediment behind dams in rivers.

Oak sleepers being fixed to the dam crest

Without water, it is impossible to test the function but ART have attempted to build this pass to work across a range of flows. Should it need altered, they will do this when water levels allow.  Hopefully this will be a big improvement as the baffles should create depth and white water and provide fish more protection as they make their way over the dam. Of course nothing will prevent poachers from trying but new HD  security cameras are to be added. Most of the undergrowth beside the fish pass will also be removed.

The incomplete Larinier Fish pass is still in place and offers a route for smolts if nothing else. In time, ART and the estate may find a solution that sees this removed or completed depending on how the new fish pass performs.

Virtually completed and now just waiting for heavy rain to bring the river and fish up. ART will monitor the performance of this over the next few months and make adjustments as necessary

Thanks to Sorn Castle Estate, Kevin Weir and Factor, Nick Wright for they assistance in bringing this about.

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