Multiple drivers of decline in the global status of freshwater crayfish (Decapoda: Astacidea)

International audienceRates 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

Recolonisation of Artificial Sediments in the Deep Bay of Biscay By Tanaidaceans (Crustacea: Peracarida), With a Description of a New Species of <i>Pseudotanais</i>

One of the more recent aims of deep-sea biological investigations has been to assess the rates and processes involved in the recolonisation of deep-sea sediments by the in situ fauna (Grassle, 1977; Desbruyères etal., 1980, 1985; Levin &amp; Smith, 1984). The spur to such initiatives has been the prospect of deep-sea mineral exploitation and the dumping of radioactive and other chemical wastes (Desbruyères etal., 1 985), in addition to the testing of hypotheses about deep-sea community regulation (Levin &amp; Smith, 1984; Smith, 1986). These experiments have shown that perturbated or defaunated sediments incubated for periods of several months are readily recolonised by deep-sea animals, although the process is much slower than in comparable shallow-water situations (e.g. Levin, 1984; Zajac &amp; Whitlach, 1982a, b). Furthermore, the resulting community of colonists may be quantitatively and qualitatively different from the ‘background’ fauna (Grassle, 1977; Levin &amp; Smith, 1984). Similar experiments have examined the effect of large ‘food-parcels’ on the in situ sediments and fauna (Smith, 1986), and a review of the responses of benthic faunas to disturbed sediments has been published by Thistle (1981).</jats:p

The white-clawed crayfish,

Great Britain and Ireland still contain some of the best stocks of Austropotamobius pallipes in Europe despite the fact that since the early 1980s many populations have been devastated by the effects of crayfish plague and compétitive exclusion by non-native crayfish. Austropotamobius pallipes is the only crayfish native to Great Britain and Ireland but in récent years a number of introductions of foreign crayfish have been made into Great Britain, for aquacultural, culinary and aquarist purposes. This has resulted in four non-native crayfish species becoming established in thewild, wheretwo, Pacifastacus leniusculus and Astacusleptodactylus , have formed large, harvestable populations, particularly in southern England. Although A. pallipes in Great Britain and Ireland is protected by national and European législation, this has not been enough to protect it from crayfish plague and, in Great Britain, from non-native crayfish. In an attempt to protect A. pallipes even further, législation has been implemented in England, Scotland and Wales which bans the keeping of ail non-native crayfish, except wherethey are being prepared for human consumption. P. leniusculus is, however, exempt from this ban in certain parts of southern Great Britain dueto its high prépondérance on crayfish farms and in the wild. Ireland already bans the introduction of non-native crayfish. It is hoped that the new législation, plus the heightened profile which A. pallipes has recently been given in Great Britain, will ensure its future survival

A review of the ever increasing threat to European crayfish from non-indigenous crayfish species

Non-indigenous crayfish species (NICS) in Europe now outnumber indigenous crayfish species (ICS) 2:1, and it has been predicted that they may dominate completely in the next few decades unless something is done to protect them. Of the ten NICS introduced at least nine have become established in areas occupied by four of the five ICS. A decline in stocks of ICS has been recorded in many countries in the face of increasing populations of NICS. Most European countries retain at least one ICS but all are under threat from habitat loss, deteriorating water quality, overfishing, climate change, and most importantly from NICS and crayfish plague. The threat to ICS is so great in some countries that “ark”sanctuary sites are being established. The three most widely-spread NICS are the North American species: Pacifastacus leniusculus, Orconectes limosus and Procambarus clarkii. These can be considered as “Old NICS”, which were introduced before 1975, compared with the “New NICS”, which were introduced after 1980, such as the North American species: Orconectes immunis, Orconectes juvenilis, Orconectes virilis, Procambarus sp. and Procambarus acutus; and the Australian species: Cherax destructor and Cherax quadricarinatus, all of which have much narrower ranges in Europe. The North American species are potentially capable of acting as vectors of crayfish plague. Outbreaks of this disease occur regularly where there are high concentrations of vectors. In addition to the NICS currently established in the wild, a further threat exists through the aquarium trade, where many American and Australian species are available via the internet and in aquarist centres. Owners of such species may discard them into the freshwater environment when they grow too big as with some Cherax spp. and Orconectes spp., or multiply too frequently as with Procambarus sp. (a parthenogenetic species). A conceptual model is presented as a possible way forward for protecting the future survival of ICS in Europe