Dowley Gap aqueduct and the neighbouring two rise lock flight on the Leeds & Liverpool Canal have both been drained as part of the work to repair leaks and replace the 3.5 tonne lock gates. Thousands of fish were collected including pike, bream, roach, tench and perch and then relocated to a safe part of the canal to preserve their population. Several white clawed crayfish, a protected species which are native to Britain, were also rehomed.
The UK's canals and rivers are home to several species of crayfish particularly where there is dry stone bank protection. Bearing a resemblance to a miniature lobster, the crayfish can grow to about 100mm long and are grey/brown in colour with a pale underside to its front claws.
Improved water quality
Once widespread across Europe and commonly harvested for food, the species has suffered major population crashes since the 1970s, due to disease and competition. Several unwelcome crayfish imports have become common around the waterways including the now widespread American signal crayfish. Despite the threats, large populations can still be found in clean, well-oxygenated rivers showing the improved water quality of canals.
Stephen Leigh, Canal & River Trust ecologist said: “Our specialist fish rescue contractors, MEN Fisheries, have removed thousands of fish using a low electric pulse which stuns the fish enabling them to be netted and moved to a safe part of the canal. We're also surveying the canal for crayfish to see how their population is doing.
"The white clawed crayfish thrives in the underwater crevices, reedy vegetation and traditional dry stone wash walls that the canals and rivers provide. The most direct way we can help them is to ensure their survival during and after major repair works like this and understand the extent to which invasive species are colonising the canals and rivers we manage.
“Many people don't realise just how important the waterways have become in providing habitats for a whole range of wildlife including these fish and crayfish species. It's therefore vital that we look after these important heritage structures, understand where the wildlife is located and then do all we can to protect them."