FALLOW DEER
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THE DISCOVERY OF A NATIVE WHITE-CLAWED CRAYFISH POPULATION IN SUFFOLK GEN BROAD Ecology of White-clawed crayfish White-clawed crayfish Austropotamobius pallipes are Britain’s only native freshwater crayfish and one of our largest freshwater invertebrates (Plate 3). They prefer clean well-oxygenated calcareous streams, rivers and lakes with a hard substrate of cobbles and stones and plenty of crevices, submerged plants, tree roots to provide refuges during the day. Crayfish are nocturnal, emerging at night to feed on a wide variety of plants, other invertebrates and detritus. They have a range of predators, such as fish, birds, rats, mink and otter and the young are also eaten by carnivorous insect larvae and nymphs such as beetles and dragonflies. As in most crayfish species, they are cannibalistic, for example, feeding on recently moulted individuals (Suffolk Biodiversity Action Plan). White-Clawed Crayfish were once common across Suffolk. However, the accidental introduction of the North American Signal Crayfish Pacifastacus leniusculus into the wild from crayfish farms since the 1970s has devastated the native population. They are larger and more aggressive than our native species and produce more young (Joint Nature Conservation Committee). They also carry a disease caused by the fungus Aphanomyces astaci known as crayfish plague against which they are immune, but which is deadly to White-clawed Crayfish. Affected animals die rapidly, often within a few days. Signal Crayfish therefore pose a serious threat to our native species through competition, predation and disease. White-clawed Crayfish are legally protected under the Wildlife & Countryside Act 1981, listed in the IUCN Red Data List and appear in Appendix III of the Bern Convention and Annexes II and V of the European Habitats Directive. They are a national (and Suffolk) Biodiversity Action Plan Species. Background to the study The last known Suffolk colony of White-clawed crayfish at Chad Brook near Long Melford was decimated by crayfish plague in July 2011 (Suffolk Biodiversity Partnership, Environment Agency). This devastating event hastened investigation of informal reports that an isolated population of native crayfish existed in the Haughley Watercourse, a tributary of the River Gipping near Stowmarket. A baseline survey was carried out in the autumn of 2011 to determine if a population existed and, if so, its extent along the river. In 2009, a pioneering native crayfish ‘ark’ site was established by the Environment Agency, Suffolk FWAG, Suffolk Wildlife Trust and Suffolk Biodiversity Partnership as a way to conserve some of Suffolk’s last remaining native crayfish (Environment Agency). Individuals were successfully translocated from the River Chad to form the basis of a new population in an isolated lake on a private farm, a site free of non-native crayfish. This conservation technique has since become more widely used and promoted (Buglife).
Trans. Suffolk Nat. Soc. 47 (2012)