The decline of endangered stone crayfish (Austropotamobius torrentium) in southern Germany is related to the spread of invasive alien species and land‐use change

Abstract

1. Declines in populations of stone crayfish (Austropotamobius torrentium) have recently been reported throughout many parts of their range, including southern Germany. To assess the rate of decline and the probable causes, a crayfish survey was conducted in the River Argen catchment, where the species was known to be widely distributed and abundant.2. Using mixed-effects regression analysis, the presence or absence of the species was subsequently correlated with riparian land-use and habitat characteristics. To elucidate the potential role of crayfish plague in stone crayfish decline, the crayfish plague-carrier status of newly discovered alien signal crayfish (Pacifastacus leniusculus) was evaluated using real-time polymerase chain reaction (PCR).3. Twenty-five of the 98 surveyed sites were colonized by stone crayfish, including only 12 of 25 sites with a previous record. The probability of stone crayfish presence was positively correlated with overhanging bank structures and the proportion of broad-leafed woods in riparian buffers. In contrast, high proportions of intensive grassland had a distinct negative effect on the probability of stone crayfish presence, and cropland also tended to decrease the probability of stone crayfish presence. Both land-use forms have significantly increased in the study area within the last decade, signifying an intensification of riparian land-use.4. Plague-carrying signal crayfish were present at two headwater sites. Crayfish plague transmission from highly resistant signal crayfish to highly susceptible stone crayfish has most likely contributed to the decline in stone crayfish, and crayfish plague outbreaks may account for up to 67% of the observed stone crayfish disappearances.5. The present study confirms a marked decline in stone crayfish populations, which is probably driven by the persistent spread of invasive alien species and intensified riparian land-use. Therefore, conservation efforts for stone crayfish should incorporate strategies to prevent and control the spread of invasive, plague-carrying crayfish, and to mitigate pressures from land use.

Recent changes in distribution pattern of freshwater crayfish in Croatia − threats and perspectives

“…Hence, such a high number of negative localities was expected, given that level of anthropogenic pressure is inversely proportional to crayfish presence (Fratini et al, 2005;Füreder et al, 2006;Weinländer et al, 2014;Chucholl and Schrimpf, 2016;Rosewarne et al, 2017). Indeed, in 61% of negative localities habitat conditions had been altered by intensive agriculture, waterbody engineering, direct municipal waste water influx, tourism, etc., while in 1%, NICS, as potential crayfish plague vectors, were recorded.…”

Population ecology of endangered white-clawed crayfish (Austropotamobius pallipess. str.) in a small rhithral river in Germany

“…Although this estimate does not exclude the possibility of false negatives at sites with very low crayfish density, it can be useful to assess the detection probability at sites with representative abundance (cf. Chucholl and Schrimpf, 2015). 24p4 F. Wendler et al: Knowl.…”

“…White-clawed crayfish (Austropotamobius pallipes species complex) is the naturally rarest species among the three native crayfishes in Germany. In contrast to the widespread noble crayfish (Astacus astacus) and the stone crayfish (Austropotamobius torrentium), which occurs throughout most of southern Germany (Souty-Grosset et al, 2006;Chucholl and Schrimpf, 2015), the native range of the white-clawed crayfish is naturally restricted to a few catchments of the Upper Rhine drainage in the southwesternmost part of Germany. These occurrences are situated along the western and southern slopes of the Black Forest and represent the northeastern distribution limit of white-clawed crayfish in central Europe (Troschel, 1997;Souty-Grosset et al, 2006).…”

The Catalogue of Freshwater Decapoda (Decapoda: Potamonidae, Astacidae, Atyidae) From the Republic of Macedonia in the Collection of Macedonian Museum of Natural History

“…This species is reported to be undergoing significant population decline in most parts of its range [37,38]. Literature data show that the main threats to the population of stone crayfish are the following: i) the presence of non-native species Pacifastacus leniusculus (Dana, 1852) and Orconectes limosus (Rafinesque, 1817); ii) the crayfish plague, caused by pathogen oomycete Aphanomyces astaci; iii) domestic and industrial pollution; iv) habitat loss and degradation (with damming, water abstraction, and channelization of rivers); v) agriculture and vi) eutrophication [37,38,39]. However, no quantitative data on the rate of decline is available and therefore IUCN Red list of Threatened Species assessed the species as "Data Deficient" [37].…”