Danger with discovery of American Red Signal Crayfish downstream of Grantham in River Witham
We wrote about invasive species a little while back, write Grantham RiverCare co-leaders David Martin and Ian Simmons.
Well, this whole subject is getting closer to home with the discovery of the American Red Signal Crayfish downstream of Grantham in the River Witham as it flows north towards Lincoln.
As ever, as a threat approaches, vigilance is paramount.
We are stressing to all those who use our rivers to ensure that they Check, Clean and Dry their gear - wellies, fishing tackle, canoes - to ensure that they are not harbouring anything that could be spread further afield either as eggs (a female crayfish can produce up to 400) or juveniles. Unfettered by natural predators, a Signal can live up to 20 years. Easily recognisable as they are a reddy brown colour and up to three inches/8cm long.
The story of how these invaders came to these shores is a classic case of unintended consequences. They were introduced in the 1960s to supplement European fisheries suffering from ‘crayfish plague’. Unfortunately, these ‘guests’ - and you couldn’t make this up - were carriers of the same disease!
In Scandinavia they are a popular delicacy and are fished for food and cash. However, with our now protected native crayfish under attack and, as we are now seeing, occupying the same water, trapping without authority is against the law. One additional problem closer to home is that the signals burrow onto riverbanks, undermining their structure, causing collapse and degradation.
Grantham RiverCare have already, in the last couple of years, discovered a number of illegal crayfish traps, which are typically the size of a shoe box, attached to the river bank somewhere where they are not expected to be found. These traps are set in an attempt to catch any crayfish, but our native breed are the most likely to be caught. We have reported our finds to the Environment Agency.
Our brief is to keep a watchful eye on the Witham, removing litter and worse from the water and surrounding streets and to monitor any spurious activities. We have worked with the relevant authorities to report some notable pollution incidents.
It is a shame that actions some 60 years ago are now coming home to roost, but with the help of all interested parties - and that includes you! - we will overcome this particular problem.