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

Abstract

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.

Marmorkrebs (Procambarus fallaxf.virginalis) are the most popular crayfish in the North American pet trade

“…Because North America is the biodiversity hotspot for crayfish (Richman et al, 2015), it is conceivable that sellers would collect and sell native crayfish species from nearby lakes and streams. Patoka et al (2014b) noted that about 5% of crayfish keepers surveyed in the Czech Republic admitted to collecting crayfish locally, but this is probably an underestimate, given that catching crayfish was illegal in that jurisdiction.…”

“…While much of the research on the sale of crayfish as pets has focused on the possibility of the introduction of exotic species (Chucholl, 2013;Papavlasopoulou et al, 2014;Soes and Koese, 2010), how those species are initially sourced can also be a concern (Calado et al, 2003;Lukhaup, 2015). North America is home to more crayfish species than anywhere else in the world (Crandall and Buhay, 2008;Richman et al, 2015), but about half of North American species pose some sort of conservation concern (Taylor et al, 2007). It is possible that within North America, collectors could harm native North American crayfish species by exploiting local populations for selling at auction.…”

Mitochondrial cytochrome oxidase I gene analysis indicates a restricted genetic background in Finnish noble crayfish(Astacus astacus)stocks

“…Nowadays the original distribution area of noble crayfish in Finland (Figure 1) is mainly inhabited with signal crayfish populations (Westman, 1991;Kirjavainen and Sipponen, 2004) causing disappearance of the noble crayfish within that region due to the crayfish plague (Viljamaa-Dirks et al, 2013), while the noble crayfish remains as stocked populations in the northern and eastern parts of Finland (Kirjavainen and Sipponen, 2004;Jussila et al, 2015aJussila et al, , 2015b.The introduced alien crayfish species, together with the crayfish plague disease they are carrying, are acting as a constant risk factor that weakens the survival chances of the native European crayfish species. Richman et al (2015) have recently stated that although approximately 30% of the world's crayfish species are threatened, the European crayfish species are facing the greatest number of risks and the invasive crayfish species are one of the main reasons for this situation. We conclude that the genetic diversity of noble crayfish in its Northern distribution range is remarkably low.…”

Australian spiny mountain crayfish and their temnocephalan ectosymbionts: an ancient association on the edge of coextinction?

“…Most Euastacus have small geographical ranges. This is particularly evident in Queensland where populations are restricted to mountain-top streams in high rainfall areas with dense rainforest cover, and are likely to have narrow thermal tolerances and limited dispersal potential [34][35][36][37]. In the face of these narrow ranges, and possible anthropogenic threats, the majority of Euastacus have been assessed by the International Union for Conservation of Nature (IUCN) [38] as endangered or critically endangered, including all northern Australian species included in this study (figure 2).…”