Freshwater Invertebrate Survey of Suffolk

Suffolk Crayfish
Native and Alien Species

A photographic guide to identification for the amateur naturalist.

Our native, White Clawed Crayfish are protected by law and you must have a licence granted by the Environment Agency in order to work with them or to survey for them. Trapping alien crayfish also needs an EA licence and if you accidently catch an alien crayfish it must not be returned to the wild it must be killed.
This legal situation can cause problems for naturalists who accidently find a crayfish in their net when kick sampling a stream, have they got a protected native or must they kill their catch as an alien? Landowners who find a crayfish species in their waterbody can always call the EA but may also want some preliminary guidance.
Therefore the Suffolk Crayfish Ark project has posted this page of photographic identification aids to help people be sure. All the photos were taken by the website author using preserved specimens provided by the Ipswich office of the Environment Agency.

The photos and text shown below may be downloaded as a pdf file by clicking on the link below.
Download Crayfish_photo_id.pdf   (2150 kb)

The Whole Crayfish

	WHITE CLAWED CRAYFISH The body of the White Clawed is relatively smooth apart from areas shown with spines. Its claws are smaller relative to body size & are rough on the top. Undersides of claws are lighter than the top (hence white clawed).
	SIGNAL CRAYFISH An American Alien The body of a Signal is smooth. The claws are large relative to body size and very strong. The claws are smooth on the top, the undersides are red. There is a prominent white or bluish patch on each claw at the top of the finger joint - the ‘signal’ patch.
	TURKISH CRAYFISH Another Alien Species The body of the Turkish is rough at the front, behind the head. Claws are long and slender relative to body size and have a rough surface.

	WHITE CLAWED CRAYFISH The sides of the rostrum of the White Clawed are smooth and converging towards the base of the small triangular apex.
	SIGNAL CRAYFISH The sides of the rostrum are smooth in the Signal and more parallel towards the small triangular apex.
	TURKISH CRAYFISH The sides of the rostrum are rough and toothed in the Turkish crayfish and are more parallel towards the small triangular apex.

	WHITE CLAWED CRAYFISH On each side there is one post orbital ridge, behind the eye, with a spine at the end nearest the eye
	SIGNAL CRAYFISH On each side there are two post orbital ridges. Each may have a spine at the end but the rear ridge may be small, more like a bump.
	TURKISH CRAYFISH On each side there are two post orbital ridges. One spine on front ridge, the rear ridge with more than one spine.

	WHITE CLAWED CRAYFISH There are prominent sharp spines on shoulders of the thorax, behind the cervical groove.
	SIGNAL CRAYFISH The Signal has shoulders with a smooth surface. It has no spines, on the shoulders of the thorax, behind the cervical groove..
	TURKISH CRAYFISH The sides of the shoulders of the Turkish crayfish behind the cervical groove are covered with spine like projections. In the photo these spines may be best seen in profile at the edge of the far shoulder at the top of the picture.