In addition, the signal crayfish is a voracious predator. It feeds on a variety of fish, frogs and invertebrates, as well as plants, and even eating its own species. The signal crayfish is well established in England and Wales, especially in the south-east of England.
They are not as prevalent in Scotland but several well-established populations have been recorded. Signal crayfish are able to disperse up and downstream, cross most natural and artificial barriers and travel over land to reach water bodies nearby.
Dispersal distances of over m in 2 days, and several hundred metres over land in one night have been recorded. Dispersal has been aided by human transfer and release of individuals, although this is now illegal. The signal crayfish occurs both in still and slow-flowing freshwater environments, including rivers, streams, lakes, reservoirs and canals. They are also able to tolerate slightly salty water.
It takes shelter under rocks and boulders, within tree roots or in burrows and cavities within banks. In the winter, adult signal crayfish shelter in burrows and enter a state of torpor. These burrows are formed of many inter-connecting tunnels, and can be up to two metres deep.
The signal crayfish has a relatively high reproductive potential, with the female of this species laying between and eggs in the autumn. The female then carries the eggs around under her tail through the winter until the spring, when the eggs hatch. Signal crayfish reach sexual maturity at about 2 or 3 years old, and can live for up to 20 years. Native crayfish are becoming extinct through the spread of crayfish plague and competition for resources.
Signal crayfish are bigger, grow faster, reproduce more quickly and are more tolerant of a wider range of conditions than the native white-clawed crayfish. They feed on fish and amphibian eggs, tadpoles, juvenile fish, aquatic invertebrates, detritus and aquatic vegetation and where present reduce populations of native species and affect food webs.
Signal crayfish burrowing can cause erosion of riverbanks. Burrows can be up to 2m deep, with many inter-connecting tunnels that weaken the bank. This can contribute to problems with flooding, livestock safety and stability of structures built on the banks.
Crayfish also take refuges from salmonid fish and predate fish eggs, which could reduce the value of commercial fisheries. This fungus-like disease is fatal to the endangered white-clawed crayfish. It spreads by waterborne spores released from infected crayfish. The spores of crayfish plague can survive for up to two weeks in damp conditions, but can be killed by drying or disinfecting.
Introducing new signal crayfish is usually the source of new outbreaks, however spores are also carried between waterways on wet fishing equipment, boots and boats. You also need permission from the landowner and any relevant angling clubs.
Native crayfish are a protected species — you can only trap them for scientific purposes and not to eat or sell. Find out more about Permission to trap crayfish. The best defence against further spread of signal crayfish is biosecurity. If you use the waterway, you need to follow the Check; Clean; Dry guidelines. Under the Wildife and Countryside Act as amended , it is an offence to release, or allow to escape, any non-native species into the wild in the UK except under licence.
If you catch a signal crayfish, bring it ashore or into the boat for humane destruction. Unfortunately, several dead and dying White-clawed Crayfish were discovered, as well as an alarming number of Signal Crayfish that had colonised the donor site more rapidly than first thought. A total of 15 healthy looking White-clawed Crayfish were recovered, but with fewer crayfish than surveyors the translocation was abandoned for the day. Specimens were collected by the Environment Agency for testing for Crayfish Plague.
The decline of what was previously regarded as the best population in Essex prompted a good deal of soul searching and fears that we had arrived too late. A much-needed stroke of good luck came the following week when, having scoured historical records, a large previously unknown population of White-clawed Crayfish was discovered on a small tributary of the River Chelmer.
Without further delay, a second translocation attempt was arranged for 14th October. After a long day in the river, a grand total of healthy crayfish was caught, spanning the age ranges from small immature crayfish to large adults. One hundred tiny juveniles were returned to the brook to restock the population. In fading light, the White-clawed Crayfish were released into their new home, where they quickly crawled under the nearest stone.
The new Ark site, which is to be joined by at least one further site in the coming year, represents a significant step towards securing the future of White-clawed Crayfish in Essex — it is hoped that populations breeding here can eventually be used to re-stock rivers in their native range.
White-clawed Crayfish are protected under UK and European law, which means that a licence is required to handle and catch crayfish. The Swedes go mad for the Crayfish season and throw big dinner parties to gorge on this little crustacean with the accompaniment of Vodka.
In the UK the Crayfish is partnered with Rocket however there are many other combinations including Valentine Warners amazing dish that includes Cobnuts, Cheese and a hot oven!! Visit our shop and buy Wild Food and Foraging Books. The meat is mainly in the tail however the claws also provide excellent food as well particularly on the big male crayfish. When you have picked the shell clean you can use that too!!
Roast the shells in a real hot oven for 10 minutes with a little Olive Oil some sliced Fennel and Onion and then place in a saucepan. Cover with water and boil the shells for the most amazing stock!! Personally, I have bought the traps and last year I tried to catch them in the River Chelmer, although it was the end of the season and I only managed to get the pots wet once.
Learn how to catch and prepare Crayfish using Pots and Traps. Please check the rules and regulations of Crayfishing as well as details on how to get a licence at the Environment Agency Website. All Posts Recipes Guides Stories. The Wild Foodie. The American Signal Crayfish how, where and when to catch them. Recent Posts See All. Catching and Preparing Crayfish using Pots and Traps. Post not marked as liked 7.
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