Worcestershire Record No. 2 April 1997 p. 4
The White-clawed Crayfish is widespread in the British Isles but absent from Scotland, west Wales, and SW England, and it is generally tends to be confined to hard alkaline waters. It prefers streams and rivers with small amounts of sediment and does not tolerate pollution or anything that depletes oxygen levels.
Crayfish look like small lobsters, measure up to 15 cm long, and are greenish-brown in colour. Crayfish feed on animal and vegetable matter, usually at night, and they are eaten in turn by a range of fish, eels, birds and mammals, including rats, otters and mink. They can form an important part of an otters diet.
Mating takes place in October or November and when the eggs are laid they are attached to the underside of the female's tail. Over-wintering as eggs the young hatch in the spring. The young cling to their mother and do not leave her until May or June. Generally the females have smaller claws than males but have wider abdomens because of the need to carry their offspring.
In Worcestershire nearly all crayfish records submitted to the Biological Records Centre have come from the Dowles Brook and its tributaries in the Wyre Forest. There are records from two other sites located at Malvern and Alvechurch. These records give a misleading view of local distribution because, compared with other sites, Dowles Brook has always been well-visited by recorders, and crayfish almost certainly are, or have been, present at other sites, particularly in the west of the county.
Our native crayfish was probably first affected in the late 1980's and since then there have been a number of catastrophic killings in the Severn catchment alone. The first river to be affected was the Dowles Brook which had its population wiped out in 1988. Later, in 1990, the River Camlad had a major killing, followed by the River Clun in 1991. Not all Signal Crayfish carry the disease and some unaffected individuals have been found living alongside our native crayfish in the Dick Brook. Apart from the issue of the fungal disease the other problem causing pressure on our native crayfish is that they do not compete very well with the Signal Crayfish for habitat and food. When the Signal Crayfish do establish themselves they can be very difficult to remove. They can undermine banks by their deep burrowing and they also eat a large quantity of fish eggs. The fact that White-clawed Crayfish are absent from the River Rea suggests that the fungal plague is probably the cause.
Many conservationists foresaw the danger that farming introduced species would bring, but action was slow in coming and is, as usual, "after the horse has bolted".
More recently, in May 1996, a statutory amendment to the Keeping of Live Fish (Crayfish) Order was made and certain restrictions now prevail:
There are exemptions for hotels and restaurants and fish markets which are keeping crayfish for direct human consumption, however they are still bound by the rules concerning the release of foreign crayfish, and the rules stating that crayfish need to be kept in secure conditions. What is disappointing is the fact that Signal Crayfish farms do not have to be licensed outside the so-called no-go areas. The only restriction outside the no-go areas occurs for new farms who use open ponds and channels. The release to these would be deemed as the "wild" under the Wildlife and Countryside Act. Presumably purpose built tanks in the countryside would not be called "wild"! This is bad news for any attempt to try and reduce the spread of the disease in these areas. Crayfish are master escape artists and this is reflected in the rigid code of practice regarding transportation. Once the disease has got a hold in an area there does not seem any way to save existing native stock which quickly succumb. As long as infected Signal Crayfish exist in the waterway there is no point in re-introducing the native species and in any case the Signal Crayfish appear robust enough to settle quite happily in our waters.
Records of either crayfish would be very welcome as a constant watch needs to be kept on this developing situation. Once again we are witnessing the dramatic effects of an introduced species on the balance of our wildlife.
Please send records to John Meiklejohn, Worcestershire Biological Records Centre, Worcestershire Wildlife Trust, Lower Smite Farm, Hindlip, Worcester. Older records would be welcome if you are sure of identification and have a reasonable fix on the locality.
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