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Chucholl C.,Fisheries Research Station Baden Wurttemberg | Mrugala A.,Charles University | Petrusek A.,Charles University
Knowledge and Management of Aquatic Ecosystems | Year: 2015

Elucidating the status of populations of endangered species of unclear origin may have important implications for conservation management. In September 2013, a population of white-clawed crayfish was discovered outside of the native range in a small artificial lake in the River Neckar catchment in southwestern Germany. White-clawed crayfish comprise two distinct lineages of yet unresolved taxonomic status, of which only the western lineage (Austropotamobius pallipes s. str.) is native to Germany. To clarify the taxonomic identity and origin of the newly discovered population, we evaluated diagnostic morphological characters and sequences of two mitochondrial genes (for 16S rRNA and cytochrome c oxidase subunit I) from two crayfish specimens. Both analyses concordantly assigned the crayfish to the southern lineage (A. 'italicus'), with the closest matching haplotypes originating from northwestern Italy, southeastern Switzerland, and Lake Plansee in Austria, where an abundant introduced population of this lineage is present. The artificial lake in Germany was reportedly stocked with freshwater mussels from this Austrian lake. It thus appears likely that A. 'italicus' was introduced intentionally or accidentally during the process. Austropotamobius 'italicus' does not naturally occur north of the Alps and thus represents a non-native taxon for Germany, a fact to be considered in its management. © ONEMA, 2015.

Chucholl C.,Fisheries Research Station Baden Wurttemberg
Biological Invasions | Year: 2016

Multiple species invasions and limited resources for management require prioritisation of deleterious effects of invaders on imperilled native species. This study prioritises the threat of six non-indigenous crayfish species (NICS) to three indigenous crayfish species (ICS) in southwestern Germany, a European region with high diversity of crayfish species and freshwater habitats. Using multivariate statistical analyses and niche-based species distribution models, the (1) contemporary and potential range overlap, (2) habitat overlap, and (3) rate of spread of the nine species were assessed. Predicted and contemporary range overlap with ICS was consistently the highest for the alien signal crayfish. Environmental niches of ICS tended to be associated with cooler temperatures (except for white-clawed crayfish), lower Human Influence Index, and higher terrain slope than that of alien Orconectes and Procambarus species, but were mostly similar to that of signal crayfish. Habitat overlap was found to be the highest between signal crayfish and ICS. In contrast to Orconectes and Procambarus species, signal crayfish also invade headwaters, where the most ICS populations occur. Range expansion during the past 15 years was the highest for signal crayfish, followed by Orconectes species. Because of the great potential to invade as-yet isolated refuge areas and spread at a high rate, signal crayfish is of the highest concern for conservation of ICS and should be primarily targeted by prevention and control measures. However, it merely represents the ‘worst of the worst’, since all NICS of North American origin are natural reservoirs of crayfish plague, a fatal disease of ICS. © 2016 Springer International Publishing Switzerland

Wendler F.,Albert Ludwigs University of Freiburg | Biss R.,Nature Conservation Agency | Chucholl C.,Fisheries Research Station Baden Wurttemberg
Knowledge and Management of Aquatic Ecosystems | Year: 2015

Sound knowledge on distribution and ecology of imperiled species is an essential prerequisite for effective conservation planning. Here, we report the distribution and autecological traits of a newly discovered population of critically-endangered white-clawed crayfish (Austropotamobius pallipes s. str.) in a small river in southwestern Germany. Using an established crayfish survey protocol, we detected white-clawed crayfish in a river stretch of 4.5 km, with an estimated abundance of 1.4 ± 0.2 indiv.·m-2. The sex ratio was even and sexual maturity was attained at approximately 25 mm carapace length (CL). Life-history traits, as assessed using Von Bertalanffy's growth function, indicate a life history most similar to populations in France, with longevity, asymptotic size, and growth performance index being higher in males than in females (11 y, 46 mm CL, and 2.8 and 9 y, 41 mm CL, and 2.7, for males and females, respectively). Estimated fecundity ranged from 9 to 135 eggs·female-1 (mean: 90 ± 28). White-clawed crayfish were also found in lower reaches of small tributary streams, of which one also featured endangered stone crayfish (Austropotamobius torrentium). A syntopic occurrence of both species was recorded for the first time within a short stretch. Implications for species conservation are discussed. © 2015 F. Wendler et al., published by EDP Sciences.

Roch S.,Fisheries Research Station Baden Wurttemberg | Behrmann-Godel J.,University of Konstanz | Brinker A.,Fisheries Research Station Baden Wurttemberg
Journal of Fish Biology | Year: 2015

The unusual yellow-finned morph of European perch Perca fluviatilis found in Lake Constance suffers more severely from macroparasite infections, including the tapeworm Triaenophorus nodulosus and the gill worm Ancyrocephalus percae, than conspecifics elsewhere. Microsatellite analysis of yellow-finned P. fluviatilis and red-finned variant recently discovered in Lake Constance revealed significant genetic differentiation. Red-finned P. fluviatilis and fish with mixed fin colour, suggested backcrosses between red and yellow-finned colour morphs, exhibit better resilience to parasite infection, suggesting that the inability of the yellow-finned morph to reject macroparasites may have a genetic basis. © 2015 The Fisheries Society of the British Isles.

Mrugala A.,Charles University | Kozubikova-Balcarova E.,Charles University | Chucholl C.,Fisheries Research Station Baden Wurttemberg | Cabanillas Resino S.,Charles University | And 3 more authors.
Biological Invasions | Year: 2015

Rapidly growing trade of ornamental animals may represent an entry pathway for emerging pathogens; this may concern freshwater crayfish that are increasingly popular pets. Infected crayfish and contaminated water from aquaria may be released to open waters, thus endangering native crustacean fauna. We tested whether various non-European crayfish species available in the pet trade in Germany and the Czech Republic are carriers of two significant crustacean pathogens, the crayfish plague agent Aphanomyces astaci and the white spot syndrome virus (WSSV). The former infects primarily freshwater crayfish (causing substantial losses in native European species), the latter is particularly known for economic losses in shrimp aquacultures. We screened 242 individuals of 19 North American and Australasian crayfish taxa (the identity of which was validated by DNA barcoding) for these pathogens, using molecular methods recommended by the World Organisation for Animal Health. A. astaci DNA was detected in eight American and one Australian crayfish species, comprising in total 27 % of screened batches. Furthermore, viability of A. astaci was confirmed by its isolation to axenic cultures from three host taxa, including the parthenogenetic invader Marmorkrebs (Procambarus fallax f. virginalis). In contrast, WSSV was only confirmed in three individuals of Australian Cherax quadricarinatus. Despite modest prevalence of detected infections, our results demonstrate the potential of disease entry and spread through this pathway, and should be considered if any trade regulations are imposed. Our study highlights the need for screening for pathogens in the ornamental trade as one of the steps to prevent the transmission of emerging diseases to wildlife. © 2014, Springer International Publishing Switzerland.

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