Status of the white-clawed crayfish, Austropotamobius pallipes (Lereboullet, 1858), in Spain : distribution and legislation

摘要

The white-clawed crayfish, Austropotamobius pallipes, is the only native species of freshwater crayfish in Spain. This species sustained a first-magnitude inland fishery up to the end of 1970's, when the crayfish plague struck the Spanish waters. It is detected an overall loss of distribution area of populations inhabiting the medium and lower reaches of the main river catchments, especially in Southern and Central Spain. The number of surviving populations can be estimated in ca. 700. Remaining native crayfish populations currently inhabit marginal areas. The populations are very fragmented, occupy short stretches, and are frequently isolated from the main river system. The current distribution is the result of a sum of different factors, i.e. crayfish plague, habitat alterations, extreme climatic drought, etc. The incidence and relative importance of each one varied during the last 15 years, with crayfish plague being a predominant negative factor in the seventies and eighties, and climatic drought in the nineties. The current trend of disappearance is a sufficient reason to consider the native crayfish as at risk of extinction. However neither the national legislation nor most of the regional government legislations have listed this species as endangered. An analysis of the legislation dealing with freshwater crayfish in Spain shows : (a) an uneven and generally low level of protection given to the native species and (b) a very complex fishing and commercialization regulations for crayfish that show significant changes from one region to another. This complex legislation, complemented with a general lack of data on crayfish populations, low levels of management and public involvement, and different strategies in regional governments regarding restocking programs with exotic species, makes a confusing situation. In order to decrease the general tendency of regression of A. pallipes a conservation program for this species needs to be implemented in Spain. This program should include a number of regulations to be followed for the particular autonomous regions of Spain. This program should include measures : (a) to restore native crayfish populations, i.e. by translocations or stocking with farm raised of summerlings, in designated areas where the risk for crayfish plague outbreaks is low, (b) to control the spread of introduced species, by controlling their means of dispersal which usually occurs by human activities, i.e. trade of live crayfish, exotic crayfish stocking programs, crayfishing, aquaculture purposes, etc., and by developing eradication methods for unwanted crayfish populations ; (c) to increase the surveillance of remaining native populations by providing the areas with native crayfish the protection level required by the European Community Directives for the Conservation of Natural Habitats and Wild Flora and Fauna (92/43/EEC and 97/62/EU) ; and finally (d) to improve public and administration awareness.