Freshwater Invertebrate Survey of Suffolk

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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.


The Crayfish Rostrum

The 'nose' of the crayfish


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.


The Post Orbital Ridge

The 'bumpy ridge' behind each eye of the crayfish


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.


The Shoulders

There is a groove behind the crayfish head (the cervical groove),
the areas at each side behind this groove are the 'shoulders', which are of course the sides of the thorax.


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.

The photos and text shown above may be downloaded as a pdf file by clicking on the link below.

Download Crayfish_photo_id.pdf   (2150 kb)


March 25, 2015 21:58