what are they?
Called crawfish in the US, they are freshwater crustaceans related to lobsters, and there are two main species in UK - the native white-clawed crayfish (Austropotamobius pallipes), and the non-native American signal crayfish (Pacifastacus leniusculus), which was introduced to Britain in the 1970s via crayfish farms, and subsequently escaped. There are a few other introduced species of crayfish, but they are not very widespread.
Signal crayfish are so called because the underside of their claws are bright red, making them easy to identify. Signal crayfish can be up to 25cm long with claws extended. If you're not sure whether what you're looking at is a signal crayfish or a native crayfish, look for the red claws - a sure sign that you're looking at a signal crayfish.
Trapping crayfish for food in the UK only involves the signal crayfish. The native crayfish is now becoming rare. They live on the beds of streams and rivers and are carnivorous, eating mainly dead creatures.
The signal crayfish can walk overland to establish itself in new waterways, and is now widespread throughout Britain.
what are the benefits?
First - getting food from the wild is always a good idea from an environmental perspective (unless we deplete the resource – but this isn't an issue here, as we'll see later). Wild food requires no pesticides, fertilisers, hormones or genetic modification - in fact, no ecological interference at all.
The second benefit is in reducing their numbers. The American crayfish is causing problems for both the native crayfish and for British waterways. Signal crayfish outcompete native crayfish because they are bigger, their eggs hatch earlier in the year, females lay up to 500 eggs (the native crayfish lays around 200), and they are less fussy about what they eat. Also, the signal crayfish carries a fungal disease (Aphanomyces astaci, commonly called the crayfish plague) that kills the native crayfish (it’s not at all harmful to humans though).
American crayfish burrow into the banks of rivers and streams to build their homes, causing erosion of the river banks.
what can I do?
You need a licence to keep crayfish in this country - see DEFRA's website - in case they escape into the wild. If you're thinking of farming crayfish, ponds now have to be indoors and escape-proof. This factsheet assumes that you're not going to keep them, you're just going to catch them from the wild. Don't put any crayfish you've caught into ponds or other bodies of water temporarily, as they could escape and colonise an area that doesn't have them.
The Environment Agency's concerns are that if people are allowed to catch crayfish for food, they will be sold to the restaurant trade, and because there is money to be made, some people might 'seed' rivers and streams that don't have signal crayfish, so that they can be harvested in the future. We share this concern, so we would encourage people never to buy or sell crayfish, but to trap them just for their own consumption.
Depending on whether the Environment Agency allow it in your area, you can make your own trap. You can make a cylinder with chicken wire, up to a metre long, and bend the ends over to form a cone that crayfish can climb into but not out of. You can do the same with willow (see photo). Trapping crayfish is a summer activity, of course. In winter, they will be hibernating in the river banks.
The trap shouldn't have an entrance of more than 95mm, because if there are otters in the area, they could get caught.
Bait the trap with something tasty for crayfish (like a fish-head), plus a brick to weigh it down, then put it into a stream you suspect has crayfish.
Check the next day. Anything other than signal crayfish, let go, and don't leave a trap in a watercourse for more than 24 hours, in case something other than a crayfish gets trapped in it. Let any native crayfish go if you've caught any. But if you catch small signal crayfish, don’t put them back (in fact it is illegal to put them back, once caught). Signal crayfish are cannibals, and if you remove only big ones, there will be nothing to keep the numbers of small ones down. The Environment Agency in Scotland have urged fishermen to kill signal crayfish on sight.
Take them out of the trap (keep fingers away from their pincers - although if they do pinch you, it doesn't hurt that much), and keep them in tubs of tap water for a couple of days to purge them of any food in their intestines.
The edible parts are the tail and the claws. Pull and separate the head and tail. Pull off the legs, then grab the end of the flesh sticking out of the tail casing and pull. Sometimes there will be pink eggs - you can eat those too. But give it a bit of a rinse to get rid of all traces of intestines and food.
Then put the claws on a hard surface and hit sharply with the back of a knife to crack them open. Grab the end of the flesh and pull it out of the claw.
You can serve with rice, toast, mayonnaise and/or any number of sauces. It looks and tastes a bit like prawn. There are plenty of recipes out there. For a meal for one person, you'd probably need the meat of 5 crayfish. If crayfish are present in that stretch of water, you can easily catch 10 in a trap each time.
UK-native white-clawed crayfish (top), and the American signal crayfish (bottom). The signal crayfish is bigger and has a small blue or white patch at the joint of the claw, and the claws are red underneath
signal crayfish displaying the tell-tale red claws
boil crayfish for 3 minutes, then leave to stand for 2 minutes
you can buy crayfish traps (talk to the Environment Agency), or you could make your own from wire or wicker
a cooked crayfish looking very much like a small lobster