Population ecology of an alien “warm water” crayfish (

Procambarus clarkii is one of the worst invasive and best-studied crayfish species worldwide, but its life history at higher latitudes is poorly understood. In the present study, the population ecology of P. clarkii was studied for the first time within its northeastern range limit in Europe (southern Germany) for a two-year period, and the findings are used to discuss several life-history parameters across different latitudes of its current distribution range. The reproductive cycle was tracked using the gonadosomatic index and reproductive traits in females and the reproductive form in males. Life-history parameters were estimated using Von Bertalanffy’s growth function. Reproduction was univoltine and occurred from late summer to autumn. A small proportion of females carried eggs throughout the winter. This contrasts with the species’ multi-voltine life cycle at lower latitudes, with year-round breeding and several reproduction peaks per year. Growth was estimated to be slower than at lower latitudes, whereas longevity, mean lifetime and size increased. These changes in life history probably reflect a general phenomenon at higher latitudes and, thus, latitudinal clines. The presented findings provide evidence that P. clarkii is able to cope well with new cold habitats by modulating its life history

Understanding invasion success: life-history traits and feeding habits of the alien crayfish Orconectes immunis

In the present study, the life history and diet of the highly successful North American invader Orconectes immunis was assessed for the first time in its introduced European range. In 2007, O. immunis population dynamics were monitored in a typical backwater habitat using unbaited funnel traps, and its life history was analysed using Von Bertalanffy’s growth function. Juveniles hatched as early as March and may attain sexual maturity at the end of their first summer. The adult population moulted up to four times during the summer months, with the non-breeding form (II) lasting for a remarkably short time period. The high growth rate of O. immunis was combined with a short longevity, which was estimated at 2.5 years. The fecundity ranged from 119 to 495 pleopodal eggs. The stomach contents were dominated by detritus, followed by macroinvertebrates and macrophytes, and no ontogenetic shift in diet was observed. The ability to prey on a wide array of invertebrate taxa presumably supports the sustained high growth rate of O. immunis. The presented data provide evidence that O. immunis exhibits a strongly r-selected life history and omnivorous feeding habits. These ecological properties have often been linked to successful invaders and enhance the invasiveness of O. immunis

First record of an introduced population of the southern lineage of white-clawed crayfish (

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

Population ecology of endangered white-clawed crayfish ( Austropotamobius pallipes

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

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

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

Identification of exotic North American crayfish in Europe by DNA barcoding

Several alien crayfish of North American origin have become established in Europe in recent decades, but their identification is often confusing. Our aim was to verify the taxonomic status of their European populations by DNA barcoding. We sequenced the cytochrome c oxidase subunit I (COI) gene fragment of individuals representing all American crayfish known from European waters, and compared the results with reference sequences from North America. Our results confirm the morphological identification of Orconectes juvenilis from a population in eastern France, and of the marbled crayfish (Marmorkrebs), i.e., a parthenogenetic form of Procambarus fallax, from south-western Germany. Sequences of most individuals of presumed Procambarus acutus from the Netherlands were similar to American P. cf. acutus, but one was divergent, closer to a sequence of a reference individual of P. cf. zonangulus. However, divergences among three American P. cf. zonangulus samples were also high, comparable to interspecific variation within cambarid species complexes. The divergence between O. immunis from Europe and America also reached values corresponding to those observed among distinct Orconectes species. Genetic variation in the American range of these crayfish should therefore be further studied. Our study shows that DNA barcoding is useful for the rapid and accurate identification of exotic crayfish in Europe, and also provides insights into overall variation within these taxa