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Native populations of the stone crayfish Austropotamobius torrentium in Tyrol (Austria) are restricted to the region of Außerfern, where the lake “Haldensee” and the river “Archbach” are known to hold intact populations. Both records are of biogeographical importance because they are the southernmost located stock of the Bavarian-Tyrolean distribution area. In addition, the “Haldensee” is one of the highest locations holding stone crayfish in Austria. “Plansee”, a lake within the Archbach catchment contains a dense population of Austropotamobius pallipes that was introduced about 80 years ago. During recent field surveys a gradual immigration of A. pallipes into the habitat populated by A. torrentium was noticed. We characterised the native populations of A. torrentium in Haldensee, its immediate outflow and in the river Archbach by means of population parameters and crayfish morphometry. The potential influence of the non-indigenous A. pallipes as intruder in the A. torrentium population is discussed.

Historical data show that the native white-clawed crayfish, Austropotamobius pallipes, was once widespread throughout South Tyrol (northern Italy), whereas recent studies identified only half a dozen remaining populations. In order to implement conservation strategies based on knowledge of genetic diversity, each of the six remaining populations in South Tyrol and one population in Tyrol (Austria) were investigated by (i) sequencing segments of two mitochondrial DNA genes, 16S rRNA and cytochrome c oxidase subunit I, and (ii) by analysing four microsatellite DNA loci. Extremely low degrees of genetic differentiation within and among the South Tyrolean populations of A. pallipes were found with mitochondrial DNA sequences. In contrast, microsatellite data displayed not only substantial genetic structure among populations, but also moderate genetic variability within four out of six populations in South Tyrol. The two remaining populations revealed a complete absence of genetic variability. Moreover, both of these populations as well as the population from Austria were fixed for single alleles at three of the four investigated microsatellite loci. Our data have important conservation implications and also show that mitochondrial DNA is not always a sufficient tool to study crayfish populations on a small geographical scale.

The stone crayfish Austropotamobius torrentium (Schrank, 1803) is widely distributed in Southeastern and Central Europe. However, this information has not been verified until recently because of: • ignorance about biogeographic notion and hydrography and • ignorance of data in the literature. Overcoming these problems during the last decade, the distribution pattern of the stone crayfish has now become apparent in Europe. It is known from Luxembourg and Germany to the west, from Turkey to the east, from Germany and the Czech Republic to the north and from Greece to the south. It is absent in the northeastern part of the Pannonian basin as well as in Poland and Ukraine. Its presence in Luxembourg and the Czech Republic may be related not to natural distribution but to introduction by humans through history. The discovery of the stone crayfish in Italy and Turkey as well as its re-discovery in France during the 1990s proves the biogeographic conception that this animal belongs to the Danubian fauna. It probably originates from the southwestern part of the Pannonian basin.

The phylogenetic relationships of the Austropotamobius pallipes species complex were assessed in several recent genetic studies by analysing sequences of the mitochondrial DNA. Although the Alpine region is known to harbour great extents of morphological and genetic diversity, none of the previous studies included populations from South Tyrol in Northern Italy and Carinthia in Southern Austria. In order to clarify their taxonomic status white-clawed crayfish were sampled from six populations in South Tyrol and three populations in Carinthia. Phylogenetic analyses are based on partial DNA sequences of the mitochondrial DNA 16S rRNA gene, which were supplemented with sequences deposited in GenBank. All surveyed individuals from the six populations in South Tyrol comprised a single haplotype that equalled the already described haplotype S3. This haplotype is distributed in Plansee (Austria) as well as several other localities in Italy and Switzerland, and belongs to the A. italicus carinthiacus clade. The investigated specimens from all three Carinthian populations also displayed one single haplotype. However, this haplotype clustered in the A. italicus carsicus clade and has not been published before. Our study clearly shows that neither Austrian crayfish populations from Plansee and Carinthia, nor populations from South Tyrol and Carinthia belong to the same phylogenetic lineage.

Genetic studies on crayfish have shown that the differences between crayfish populations can be greater than it is assumed at the first view. Studies have demonstrated that some of these differences are not only found in the genome but are also expressed in the morphology of crayfish. Statistical analysis of a large set of morphological parameters from several autochthonous crayfish populations of Astacus astacus (Linnaeus, 1758) and Austropotamobius pallipes (Lereboullet, 1858) were applied in order to define distinct characteristics of different populations. Preliminary results of a multivariate discriminant analysis suggest that some morphological parameters are useful attributes to identify distinct populations. A positive correlation was obtained between carapace shape, described as the ratio postorbital length/width of carapace, and carapace curvature. Our results showed that the development and application of methods to characterize the uniqueness of individual populations is important, especially when they may have adapted in various ways to specific environmental conditions due to separation for a long time.

In Tyrolean like in other European freshwaters, crayfish populations decreased in numbers and qualities. They are today regarded as endangered animals. The Astacus astacus (Linnaeus, 1758) population of historical evidence in Tristacher See and its out flowing stream Tristacher Seebach (mentioned already by Emperor Maximilian I in 1504) became extinct in the late 1990s. After the restoration of the stream we started a species conservation programme with various specific protection measures, including breeding and restocking of young-of-the-year and adult A. astacus. Females, after having released their young in the hatchery, were stocked together with males in a 200-m-section of Tristacher Seebach, previously populated by A. astacus. In October, the young-of-theyear crayfish were released in another area of the same stream. To show the importance of habitat diversity and shelter, four sites for introduction were selected describing a gradient of habitat diversity. We monitored general characteristics of the population (sex, size, densities) and compared them to habitat conditions. Individual crayfish were tagged with gloss-paint pens to allow an observation of their movements between the different sections over the summer months. We found significant results when migration behaviour, population assemblage and habitat conditions were compared. Males frequently moved longer distances than females. Migration length corresponded to the gradient of available structures and shelter. Heterogeneous riprap was somewhat preferred to artificial shelter like bricks or plastic tubes. Sections without additional shelter showed almost no presence of crayfish. Sex and size distribution within assemblages appeared also to be affected by habitat conditions. Our results indicate the importance of monitoring in species reintroduction projects, as this research demonstrated the immediate effect and importance of habitat structure and affirmed the success of the protection measures. This may in fact help to avoid future failure.

Rapid decline of crayfish in European freshwaters and continuing threat necessitate integrated actions in conservation and management of native crayfish populations. Besides biological reasons (diseases, plague), the impact of toxic and harmful substances (fertilisers, herbicides) or wastewater effluents, habitat alteration or fragmentation have been responsible for their decline in some regions. The same is true for the region of South Tyrol, where compared to previous investigations, only 10 of a former total of 15 crayfish locations in the water bodies could be affirmed. Although two new populations of the non-indigenous Astacus astacus were detected, the native Austropotamobius pallipes continues to decline. While many investigations have focused accurately on causal coherences for the decline of native populations, the properties of crayfish facilitate to reverse the situation. In a few examples, the potential of Austropotamobius pallipes, the native crayfish in South Tyrol, as “surrogate species” for effective biological conservation is discussed. Given the various adequate attributes of freshwater crayfish as surrogate species (including indicator species, umbrella species and flagship species qualities), they may help to advance not only the crayfish situation itself but also freshwater ecosystem properties in general.

The use of indicators is among the most important and popular instruments of environmental control and nature conservation. Within the EU project “Craynet”, integrated research projects and general discussions have been presented with the aim of monitoring European native crayfish as indicators of biodiversity. Underlying many presentations on crayfish was the implicit assumption that Austropotamobius species were bioindicators for good water quality. With this as background, the Round-table discussion at the meeting in Kilkenny opened with two general questions, (1) what is a bioindicator and how well do crayfish, and especially Austropotamobius pallipes, match this concept? and (2) are other concepts such as “surrogate species” (sensu CARO and O’DOHERTY, 1999) more appropriate? The suitability of A. pallipes to be classed as a bioindicator was questioned by discussing its general tolerance to pollution, and the roles played by eutrophication and organic enrichment, water chemistry, chemical pollutants, and habitat. The value of A. pallipes as a bioindicator still remains debated; we are aware of many studies and statements of varying objectivity from fairly good to poor examples defining this species as a good to weak bioindicator. It seems that A. pallipes has potential as a bioindicator, however, perhaps only when we are able to narrow and define its tolerance levels. One conclusion of this interesting discussion is that a much better keyword, instead of “ bioindicator ”, would be “ flagship species ”, not least because of their “ cultural heritage ” value.

Twenty-eight freshwater crayfish were collected from 8 streams and one small lake in the province of South Tyrol (North Italy) from autumn 1999 to spring 2001, in order to investigate the presence of branchiobdellidans. At 6 of the streams the white clawed crayfish (Austropotamobius pallipes italicus) was collected, while the noble crayfish (Astacus astacus), the exotic species: signal crayfish (Pacifastacus leniusculus) and spiny-cheek crayfish (Orconectes limosus) were respectively caught at the other 2 streams and at the lake. Except for O. limosus, branchiobdellidans were observed on all crayfish examined. On noble crayfish, specimens of Branchiobdella italica and Branchiobdella hexodonta were found on the same host. Branchiobdella italica was largely recovered from all white clawed crayfish. The specimens of signal crayfish were found to carry only Xironogiton victoriensis.

Freshwater crayfish are among the most endangered animals in Europe. Information on freshwater crayfish in the Italian province of South Tyrol was insufficient until the recent studies on their historical and present distribution, which showed the alarming facts that only 15 standing and running waters remained as freshwater crayfish habitats, carrying the native Austropotamobius pallipes and the allochthonous Astacus astacus, Orconectes limosus, and Pacifastacus leniusculus. Still ongoing alterations or degradation of water bodies have contributed to the high degree of population decline and loss. While the exotic crayfish O. limosus and P. leniusculus could develop higher densities, most of the autochthonous A. pallipes populations were weak and consisted only of a few individuals. Three populations of A. pallipes, however, remained in a good condition, representing potential sources for recovery programs. Protection measures currently carried out in South Tyrol involve breeding, restocking and reintroduction of autochthonous A. pallipes individuals in ecological intact water bodies.

Captive breeding and crayfish culture are considered important measures in species protection activities. Thus, knowledge on optimal feeding of crayfish in captivity is needed in order to secure minimal mortality and prevent detrimental effects to health. To optimize conditions of crayfish prior to subsequent stocking, feeding trials were conducted with the aim of investigating the connection between food intake, food preference and temperature under near natural conditions. During a five-month period, noble crayfish were fed on fish, carrots, algae and chironomid-larvae according to a pre-defined rotation system, whereby the ambient water temperature ranged from 5 °C to 13 °C, following the natural temperature regime. The results of these feeding trials demonstrate a direct correlation between rising temperature and increasing food intake for water temperatures exceeding 8 °C. Food intake is further influenced by the variety of food items available at any one time. The results also confirm that Astacus astacus has a strong preference for fish and that alternation of food types has an impact on consumption. Our results prompt the following recommendations for optimized feeding conditions of crayfish in captivity prior to their release: (1) a balanced diet containing not only plant tissue but also a significant proportion of animal tissue and (2) the amount of available food must be adjusted according to the carapace length of the crayfish.

Indigenous crayfish species (ICS) are under threat in Europe; due to competition from invasive non-indigenous crayfish species (NICS) from crayfish plague, which is carried by introduced American crayfish, and habitat degradation. We focus on the white-clawed crayfish Austropotamobius pallipes and stone crayfish A. torrentium. Surveys in many countries have shown the accelerating rate of loss since the late 20th century; concurrent with rapid spread of NICS by human-assisted introductions and natural expansion. Remaining populations of ICS are becoming fragmented. As NICS become ever more extensive, it will become progressively harder to retain populations of European ICS. Legal protection alone is not sufficient against the major threats from NICS and crayfish plague. We recommend catchment-scale risk assessments, to identify threats and to guide action plans: (1) populations of ICS where loss is inevitable, (2) those at some risk that can be made more secure by various measures and (3) existing or new isolated populations that can be kept secure, “ark sites”. Resources can be targeted to achieve specific conservation goals. Ark sites are likely to offer the best chance for survival of both Austropotamobius species, where there are invading NICS. We discuss constraints and opportunities and the need for public involvement.

Crayfish are among the largest and most threatened invertebrates in freshwater habitats. Due to their size, behaviour and feeding activity they may affect structure and function of aquatic ecosystems and their organisms. Despite their importance in many freshwaters and available information on their ecology for several species little is known about the European crayfish Austropotamobius torrentium. In order to evaluate the potential effects of indigenous crayfish presence on the structural and functional composition of the zoobenthic community, we measured population size and densities of three A. torrentium populations and compared macroinvertebrate assemblages and physicochemical parameters in three streams with and three without crayfish. The experimental setup considered crayfish effects at a large scale in defined reaches of pristine headwaters in association with the whole benthic fauna under natural conditions. Presence of A. torrentium significantly affected zoobenthic abundance, diversity and the relative proportions of functional feeding groups. In crayfish streams, especially Trichoptera and collector gatherers were more abundant and diverse, while sites without crayfish had significantly higher abundances and diversities of shredders and wood feeders. Our study provided strong evidence that the presence of the indigenous crayfish A. torrentium had important effects on the trophic cascades of headwater stream communities.

A round table discussion involving 25 researchers from 11 European countries was organized during the congress “European Crayfish: food, flagships and ecosystem services” (held in Poitiers, France, 26–29th October 2010) to consider current activities dealing with management of indigenous crayfish species (ICS) with special regards to their culture, restocking and conservation strategy. In the following opinion paper, we attempt to summarize best practice of current conservation strategy as well as advantages and disadvantages of applied tools and approaches for listed species or species complexes. The development of conceptual models for the protection of ICS in Europe seems to be necessary; however, currently recommended approaches of conservation strategy of ICS differ according to countries and species. The different approaches to conservation of Astacus astacus and species in the genus Austropotamobius, such as genetic diversity, captive breeding, origin and characteristics of stocking material and establishment, as well as long-term objectives of sanctuary or “ark” sites, were highlighted during the round table discussion.

Abstract: Water temperature is a physical property influencing abiotic and biotic parameters in an aquatic ecosystem. In different Central European rivers and lakes, a general trend of water temperatures in the range of +0.05 to +0.8 °C per decade was identified. Our case study analyses whether similar patterns apply to the headwaters of the Volga River, in the East European plain. Based on a dataset of water temperatures for 2008–2015, we investigated the spatial and temporal distribution of water temperature along the Tudovka River and estimated backward as well as predicted future changes from development scenarios throughout the 21st century. Stochastic models were applied to track trends and variations in water temperature. Furthermore, the correlation between water temperature and air temperatures was used to model historical water temperatures and to predict possible changes in the future, under the effects of climate change. Based on climate change scenarios, an increase of the mean water temperatures as well as changes regarding the ice cover can be expected until the end of this century. The conditions described for the headwaters of the Volga River system represent a valuable dataset for medium and large rivers in the East European plain and serve as a basis for future management. [ABSTRACT FROM AUTHOR]