Rates of biodiversity loss are higher in freshwater ecosystems than in most terrestrial or marine ecosystems, making freshwater conservation a priority. However, prioritization methods are impeded by insufficient knowledge on the distribution and conservation status of freshwater taxa, particularly invertebrates. We evaluated the extinction risk of the world's 590 freshwater crayfish species using the IUCN Categories and Criteria and found 32% of all species are threatened with extinction. The level of extinction risk differed between families, with proportionally more threatened species in the Parastacidae and Astacidae than in the Cambaridae. Four described species were Extinct and 21% were assessed as Data Deficient. There was geographical variation in the dominant threats affecting the main centres of crayfish diversity. The majority of threatened US and Mexican species face threats associated with urban development, pollution, damming and water management. Conversely, the majority of Australian threatened species are affected by climate change, harvesting, agriculture and invasive species. Only a small proportion of crayfish are found within the boundaries of protected areas, suggesting that alternative means of long-term protection will be required. Our study highlights many of the significant challenges yet to come for freshwater biodiversity unless conservation planning shifts from a reactive to proactive approach.
The distribution of crayfish in Europe is examined using information from a variety of sources mainly for the last two decades. All European countries have at least one indigenous crayfish species (ICS), many with large stocks, and most countries in Western Europe have at least one non-indigenous crayfish species (NICS). Some species termed indigenous in certain countries may have been introduced in relatively recent times. However, the meaning of the term indigenous (native) varies between countries. NICS continue to expand their ranges and present a continued threat to ICS through competition and transmission of diseases, notably crayfish plague. The current high level of interest in crayfish means that many countries are monitoring their crayfish situation and, where necessary, taking steps to renew stocks of threatened indigenous species, some of which are apparently on the verge of extinction. A more regular monitoring programme for European crayfish as a whole is needed if the demise of indigenous species is to be prevented.Key-words : crayfish, indigenous, non-indigenous, taxonomy, distribution, Europe. DISTRIBUTION GÉOGRAPHIQUE DES ÉCREVISSES EN EUROPE ET DANS CERTAINS PAYS ADJACENTS. RÉSUMÉLa distribution géographique des écrevisses européennes est examinée à l'aide de données recueillies en majorité au cours des deux dernières décennies et provenant de diverses sources. Tous les états européens ont au moins une espèce d'écrevisse indigène (en anglais, indigenous crayfish species -ICS), souvent avec des stocks importants. De plus, la plupart des états en Europe de l'ouest ont au moins une espèce d'écrevisse nonindigène (en anglais, non-indigenous crayfish species -NICS). Dans certains pays, des espèces reconnues comme étant indigènes peuvent en fait avoir été introduites Bull. Fr. Pêche Piscic. (2002) 367 : 611-650 -611 -Article available at http://www.kmae-journal.org or http://dx.doi.org/10.1051/kmae:2002055 récemment. La signification des termes « indigène » et « natif » est variable entre les pays. La distribution des NICS continue à s'étendre et menace sans cesse les ICS à travers la compétition et la transmission de maladies, notamment la peste. Le regain de l'intérêt porté aux écrevisses dans plusieurs pays européens engendre une meilleure gestion des stocks qui se traduit par une surveillance accrue des populations et le renouvellement des populations menacées des espèces indigènes, qui sont parfois en voie de disparition. Un programme de surveillance pour toutes les écrevisses européennes sera nécessaire pour prévenir la disparition des espèces indigènes.
The farming of freshwater crayfish (astaciculture) is mainly carried out in the southem states of the USA, and in Australia and Europe. Production levels Vary with climate but are in the region of 40000 to 60000 tonnes per annum. In addition, at least an equivalent amounts is harvested from the wild, particularly in North Amenca, China, Australia, Kenya, Turkey and Europe. Crayfish farming is usually cithcr of an extensive (ranching) or semi-intensive nature, intensive methods being infrequent, except for the rearing of juveniles for stocking (or restocking of natural waters depleted of crayfish). As crayfish do not have larvae and are polytrophic, they are relatively easy to rear, although fecundity is much lower when compared with other cultured crustaceans. At least 85% of world production is based on the red swamp crayfish, Procamharus clarkii, mainly from Louisiana and other southern USA states, but also from China, Kenya and Spain, where it has been introduced. In Australia, three species are of aquacultural importance, the yabbie, Cherax destructor; the marron, C. tenuimanus; and the red claw, C. quadricarinatus. Some very large production units have been built but none have lived up to their promise. The red claw is thought to have considerable aquacultural potential, but, being a tropical species, needs warm water for good growth. In Europe, the only endemic species cultured to any extent is the noble crayfish, Astacus astacus, mainly as juveniles for restocking. It fetches a higher pnce than other crayfish. The North American signal crayfish, Pacifastacus leniusculus, has been introduced to most European countries, but farmed production is relatively low. About 98% of crayfish consumed in Europe come from extensive systems or the wild harvest. European crayfish markets were upset by the collapse of the Turkish crayfishery (based on Astacus leptoductylus) due to overfishing and disease in the mid-1980s. The environmental impact of crayfish farrning is most noticeable in Europe. Crayfish plague, introduced from North America last century, haî devastated populations of the native species in many countries. 1ts spread has been exasperated by the translocation of foreign crayfish (and probably by fish) for aquacultural purposes. In addition, introduced crayfish frequently escape into the wild and form large populations, often in direct competition with native species. Burrowing and prolific species, such as P. clarkii, can also do considerable environmental damage.
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