It is illegal to release a NNS (Non-Native Species) into the wild – this includes signal crayfish, so if caught, they must be killed humanely and not released back into the water, even the water from which it came.
If you catch one, they should be killed, maybe with a stone, and buried as it is also illegal to transport them without a license.
It is illegal to remove from any water an animal under the protection of the law – this includes the native white clawed crayfish. If you accidentally catch a white clawed crayfish, you MUST return it unharmed to the water from which it came as quickly as possible.
About the Red Signal
The life cycle of the signal crayfish is quite simple, mating takes place during autumn. The eggs, of which there are about 200, are held beneath the tail of the female until they hatch in the spring. The young are carried by the female until, after 3 moults, they leave the female. Signal crayfish live for about 20 years.
Signal crayfish are reputed to hibernate during winter cold periods, but river keepers (middle Kennet) and other anglers attest to crayfish being active during the whole year. However one river keeper doing some work in Hampshire found a hibernating crayfish at the bottom of a 6 foot long tunnel. It is this tunnelling that can cause problems with river banks. The photo above is of a soft clay bank that has been tunnelled by crayfish. Crayfish activity is lessened during cold periods, but not totally subdued.
Crayfish often use the tunnels vacated by voles and rats. But if holes are not available, crayfish make excellent tunnellers.
Later I will talk about the signals of a signal crayfish. Note the white patch on each of the large front claws of the crayfish in the image below – these are the signals.
Crayfish eat just about anything, technically they are onmnivores; they will eat anything from smelly meat (garlic sausage and Frankfurter) to rotting fish, yuuuukkkk. They eat other crayfish, water-vegetation and detritus of rotting vegetation on the river bed. Apparently they do especially enjoy getting stuck into a nice batch of fresh fish eggs.
Identifying signal crayfish:
Perhaps this guide is for anglers who are most likely to come into contact with crayfish. If you want to go into this in more detail, you will need a licence from the Environment Agency to trap crayfish. So you are out fishing and detect a bite you come up sith this horrible looking thing, a bit like a small lobster – what is it? Look at the top of the crayfish – does it have “signals”? The finger joints of the signal crayfish: the main joint on the big front claws, will have white or pale blue patches (see images). Is the shell mostly smooth? White clawed crayfish and Turkish crayfish are covered in bumps. Turn it over, and is the underside of the claws bright red to pinkish red? Signal crayfish have red or red-pink claws. White clawed crayfish have dirty greyish-pink to white undersides.
Looking at the image on the right, this shows the claws of the signal crayfish, note the white-blue patch at the finger joint, and the bright red colour beneath the claw.
Getting down and dirty with crayfish. Look closely at the eye socket, just behind the eye are two small bumps (post-orbital ridges). This is only visible in close-up shots of the cheek, or side of the face, but you will see in the circled area a bump behind the eye, followed by a second, smaller bump. This is one of the identifying features of the signal and the Turkish crayfish. White clawed crayfish only have ONE bump.
Signal crayfish antics:
Signal crayfish are excellent at getting around. They will walk, climb, burrow and tunnel. Often migrating long distances over land to move from water to water. To prove a point, during a recent crayfish soiree a crayfish was observed to attempt to climb the 30 degree slope of a weir. The concrete was slippery with algae, the water fairly fast running and despite, during our observations, the beast being washed back down several times, it continued in an attempt to climb the slope. In the images below I have tried to give an impression of just how persistent the thing was. Click any image for a larger view. It finally made it at about the fifth attempt.
Thanks for the above info and use of photos to John Boulton and the site www.sta-lincolnshire.org.uk