Inhaltszusammenfassung

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 habita...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. Copyright (c) 2015 John Wiley & Sons, Ltd. » weiterlesen» einklappen

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