DESTRUCTIVE crayfish that were introduced to the UK four decades ago and threaten native species appear to have infiltrated a dale reservoir.
Teesdale resident Shaun Hall came across six dead crayfish on the shores of Cow Green, near Middleton-in-Teesdale. Mr Hall said there were a number of them on the edge of the water but was unsure whether they were signal Crayfish, an invasive American species originally introduced to the UK to be farmed for food, or the native white-clawed crayfish.
Ben Lamb, general and catchment partnership officer of the Tees River Trust, said he was in no doubt the photo of one of the crayfish was a signal. It had turned blue after dying.
Mr Lamb added: “If they are in the reservoir, there is not a lot that we can do about it. I’m going to let the Environment Agency know, but as far as I’m aware no one knew they were there.”
Signal crayfish were introduced to the UK in 1976 but escaped into the waterways and have spread rapidly ever since. The invader is driving the native variety towards extinction through the spread of crayfish plague and competition for resources.
They can cause significant damage to the environment. Signal crayfish are larger than the native variety and burrow up to two metres into riverbanks with interconnecting tunnels that weaken the bank and can contribute to flooding problems.
Although sightings of signal crayfish had been recorded in the River Tees at Middleton-in-Teesdale by the Non-Native Species Secretariat, this is the first known report of them in the reservoir.
Mr Lamb said although the problem has been around for years, it has been treated more seriously in recent times. He added: “Putting together the invasive species list is a step in the right direction, and part of that has been delivering locally but needs concerted effort. The Government is going to have to invest a lot more money to get rid of these invasive species.
“Unless they take these things seriously and fund eradication schemes the problem is a going to continue. They have an economic impact as well as an environmental one. If a farmer is losing bank sides, that has an economical impact. The increased sediment from bank erosion has a knock-on effect for water treatment and general loss of ecology.”
Mr Hall said he only noticed the crayfish on the Teesdale side of reservoir and in the vicinity of dam.
Although the species is a problem in the waterways anyone wishing to trap them needs a trapping licence.
Fishermen who inadvertently catch any cannot release them back into the water and are advised to crush them.
