Invasive crayfish in the UK: is a quieter species being underrated?
· BehindLines newsroom
The narrow-clawed crayfish (Pontastacus leptodactylus), little studied in the UK, may weigh on its prey as heavily as the signal crayfish, a well-known invader. That is the conclusion of a University of Leeds team, published on 3 July 2026 in the journal Biological Invasions and brought to a wider audience by Phys.org on 5 November.
The experiment
Lead author James Hodson and colleagues including Matthew Harwood and associate professor Josie South compared the two species at four temperatures: 9, 12, 17 and 22 °C. In the lab, they measured how much prey each crayfish eats at different prey densities, using a small native crustacean, Gammarus pulex, as the prey. Both species fed heavily on it at every temperature. The researchers then combined these measurements with population abundance to compute a "relative impact potential": for the narrow-clawed crayfish it climbs with temperature up to roughly 17 °C.
Why 17 °C matters
According to the Leeds release, still waters in Britain reach about 15 to 20 °C in summer, a range close to that peak. The authors consider the species a potentially damaging invader both now and in a warmer climate. The release adds that, unlike the signal crayfish, it does not carry crayfish plague. The two sources contradict each other on its field populations: the Leeds release says they are usually smaller than those of signal crayfish, while the journal paper reports it was more abundant at the sampled sites (a West Yorkshire reservoir versus a North Yorkshire stream), results the authors say apply only to those localities. This article does not settle the point.
What the authors recommend
Eradicating an established population is hard, so the team favours stopping spread into neighbouring waters. It asks regulators to spot possible invaders early and to reassess management of this species. Josie South stresses that a lack of data on how organisms react to warming leaves the country exposed to species once thought harmless. The results come from experiments at four temperatures, not from measurements in the wild.