The Noble Crayfish (Astacus astacus Linnaeus, 1758) is a widespread species occurring in stangant and running water bodies of the moderate climatic zone of Europe. Its populations has undergone significant declines in numbers due to anthropogenic changes of water quality, introduction of invasive non-indigenous species, crayfish plague, habitat loss and over-harvesting in many regions. Estimates of the rate of decline in most countries are very high during last decades (globaly decline rate of 50 - 70%. Successful re-stocking programs in some countries reduced the decline, but the species is still considered as Vulnerable under criterion A2ad of IUCN (see Jedlička et al. 2008).

While records on the crayfish distribution in Western and Eastern Slovakia are more abundant, there are a large gaps in recent data from Central Slovakia. There are only several records on the crayfish occurrence on websites of municipalities from the region or at websites on nature compiled by amateurs, where is very reliability and lack of supporting information (exact place and date of observation, sex or size of reported crayfish etc.). Among unique records of the crayfish are records of the State Nature Protection staff, fishermen and student theses. Among records on crayfish occurrence in adjacent areas, Urban et al. (2008) found remains of crayfish in otter excrements near the Málinec water dam and at some other sites of Poľana Mts (westward from our ATBI area). Hudec (1994) published information on distribution of crayfish in Eastern Slovakia.

In Hungary, there are several records on distribution of Astacus astacus in the catchment of Sajó (Slaná), Bodva and Hernád (Hornád) rivers southward form the Slovenský kras NP (Thuránszky & Forró 1987, Kovács et al. 2005).

A large scale inventory of species within the ATBI+M Gemer (All Taxa Biodiversity Inventory nd Monitoring) activities supported by the EDIT (European Distributed Institute of Taxonomy) network allowed us to make also inventory of recent distribution of freshwater crayfish in the region of three karstic national park situated in Central and Eastern Slovakia, in Slovenský raj, Muránska planina and Slovenský kras.

In order to make inventory and verify older information on the occurrence of crayfish presence in the area of ATBI Gemer region, baited traps and manual collection of crayfish were used. Traps were placed in stagnant waters of ponds and dams at a depth of 1 – 2 m with bait. Traps were exposed for one or two days. We monitored also the stay tracks of crayfish, like faeces of predators (otter mostly), tracks on the unveiled bottom of lakes and presence of carapaces and chalae on the banks of water bodies.

List of sites with geographic coordinates and altitudes is presented in the Table 1.

One leg of each specimen was removed and preserved in 96% etylalcohol for furher analyses in laboratory.

Specimens were identified according to manuals and keys of Fuereder &Machino (2002) and Souty-Grosset et al. (2006).

Area description

All three ATBI Gemer core areas, NP Muránska planina, NP Slovenský raj a NP Slovenský kras, are mountains of typical karstic character – calcareous blocs – mountain plateaus sorrounded by steep slopes with rich spring underhill. All tree mountain areas are broken by deep gorges with typical climatic inversion and separated by mountians and lowlands of another geological structure and origine (mostly of volcanic, metamorphed or sedimentary character).

Whole the studied area belongs to the main catchment of the Danube river, but river network belong to three independent tributaries of the Danube, Hron river, Slaná river and Hornád river (last two flow into Tisa river first).

Noble crayfish, Astacus astacus (Linnaeus, 1758) was found at 5 sites from altogether 86 sites. The overview of all sampling sites is presented in the Table 1, positive sites with details in sampled crayfish is summarized in Table 2 and shown on the map in Figure 1.

Rare occurence of crayfish in the studied area can reflect the historical events of last centuries (largescale mining areas as well as local middleage ore excavatian and metal production, large deforestation and extensive industrial development, intensive agricultural production and large population growth during last century).

Populations of crayfish are isolated and bound to several isolated stagnant water bodies or to upper sections of streams, where the water quality was not deteriorated by human influence.

Presence of crayfish in the large water dam the Palcmanská Maša is known for decades in the upper part of the dam (near inlet ot Hnilec river under village Stratená), however according to information of local people, they did not reported crayfish there for many years. Occurrence near the village Dedinky can results from higher level of available food from the breeding plant of salmonid fish and due available shelters between large rock at the bank of the water reservoir (Figure 4). In this water reservoir, crayfish were tradiotionaly mentioned in the inlet of Hnilec river near Stratenská Píla, however according to inforation from local people, no crayfish were observed there during last decade.

Among newly reported sites, crayfish were found in abandoned and awashed hoisting shaft near village Ploské (Figure 5). The water body is surrounded by beech and fir forests and there is the most abundant population of Astacus astacus reported in the region during our study.

Fish ponds used for commercial as well as leisure fishing belongs to places where crayfish frequently live. Fishponds near village Muránska Lehota are known as stable site of occurrence of crayfish (Figure 3).

Fishpond below city Tisovec is a new site of known crayfish occurrence (Figure 2).

During sampling of freshwater insects in streams at area southward from the National Park Muránska planina, we found crayfish in the stream below village Ratkovské Bystré. The stream bottom is covered by blue ceramic glas-like fractions originated from local metal ore processing in the past, so the occurrence of crayfish here was unexpected. Moreover, this locality is the only site where the presence of Astacus astacus was reported in running waters – all other records presented in this study do origin from stagnant water (water dam reservoir or fish ponds).

Surprisingly negative results we got at the holow basin north and north-earstward form the National Park Slovenský raj, where no crayfish were reported by us in streams and stagnant water. Rare reports on the local crayfish occurrence can be found at some websites of municipalities and there are also several inacurate records in the files of the State Nature Conservancy, but our investigation did not proved crayfish presence in large part of the Spiš region.

Many municipalities (e.g. Dobšiná, Hrabušice etc.) have crayfish listed on their environmental agenda, regional development plans or at the web sites, but the real validity of such an information is doubtful.

In spite many negative records, noble crayfish, Astacus astacus (Linnaeus, 1758) probably do occur in some isolated places in the regions of Spiš and Gemer which can serve as a species refugies, and further attention should be given to detailed inventory of its occurrence. This study was focussed mostly on its presence in running waters and only few stagnant water bodies were sampled.

While the noble crayfish is the only crayfish species reported in the region, we assume the presence of Astacus leptodactylus Eschscholz, 1823 in area neaby the National Park Slovenský kras (e.g. fish ponds in south-eastern direction).

Research was supported from resources of EDIT ATBI+M (All taxa biodiversity invertory and monitoring), by the project Astacus (Distribution, population biology and ectoparasites of crayfish in western and central Slovakia) nr. 1/4342/07 as well as project of grant for youg scientists provided by the Comenius University. Authors are obliged to staff of the national parks as well as to students and colleagues for their help in sampling.