This is the only crayfish species native to the UK and Ireland. It lives in streams, lakes and rivers, especially hard water areas that are unpolluted and free of sediment. It was widespread until the 1980s; since then a variety of factors have lead to its decline.
Crayfish are nocturnal and omnivorous. They grow up to 12cm in length and are prey to many different creatures. Fish (such as perch and trout), birds (such as heron), rats, mink and otters all eat crayfish. Other crayfish may even eat a crayfish that has recently moulted.
Breeding is usually in the autumn; the eggs become attached to the underside of the female's abdomen. They hatch in late spring or early summer into relatively immobile juveniles and must moult twice more to gain adult shape. Juveniles may moult seven or eight times more in their first year, but adults generally moult once a year. Crayfish live seven to twelve years.
Crayfish plague is one of the reasons for the decline in white-clawed crayfish populations, especially in the South. The disease is caused by a fungus, Aphanomyces astaci. It has been known to destroy local crayfish populations in a matter of days.
Another of the main reasons behind the decline is the growing population of signal crayfish. As well as being larger and faster-growing than native crayfish, competing with them for food and sometimes preying on them, signal crayfish are often host to crayfish plague without being affected by it. Signal crayfish are thought to have accelerated the spread of crayfish plague considerably.
Pollution and loss of habitat have also affected white-clawed crayfish populations.
There is just one remnant population of white-clawed crayfish in Cambridgeshire.
Sightings of white-clawed crayfish should be reported to the Environment Agency.
Crayfish plague may be spread by spores on nets and waders, so if these are used where there is a non-native crayfish population or where crayfish deaths have occurred, they should be left to dry out completely, then treated with disinfectant and rinsed before further use.
For more about white-clawed crayfish, see:
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