Fishtek are continuously striving to find novel solutions to improve fish and eel passage at various types of barriers on our rivers and estuaries. We are currently working with Jacksonhyder on a Environment Agency led project to improve fish and eel passage at various sites on the River Thames where gated weirs are undergoing refurbishment. Each site requires a bespoke solution, given the complexity of the refurbishment works, the range of species for which passage is required and the flow characteristics of the site. Works were recently complete at Caversham weir – the first of a number of sites – and we returned last week to inspect the finished product. Three undershot sluice gates were replaced having reached the end of their life cycle and as a part of the works an eel pass was installed, as required by the Eels Regulations 2009.
The images below show the newly refurbished sluice gates alongside the eel pass that was designed and fabricated by Fishtek. It was a prerequisite of the design that the eel pass did not interfere with the operation of the sluice gates, given their importance for flood alleviation, and we therefore carefully designed an eel pass that passed through the abutment adjacent to the gates. This required coring of the concrete abutment and fabrication of a bespoke cylindrical section of eel pass to sit inside the core. Downstream of the cored section there is a typical rectangular section of eel pass that is lined with bristle crawling substrate and has a hinged lid, which allows for access but limits predation of eels. Upstream of the core there is another novel feature – a removable debris screen that prevents the entertainment of debris into the pass and limits maintenance needs. The conical screen deflects debris away from the pass whilst letting flow in and eels out. It is secured with a single padlock that is attached to the handrail and a ladder-run type handle allows for easy and safe operation from the bridge deck.