Biology and invasive spreading of signal crayfish (Pacifastacus leniusculus) in the Vysočina Region

This thesis deals with the issue of non-native crayfish species in Europe, focusing mainly on the Czech Republic. The main species of interest was the signal crayfish. Its biology in relation to invasive spreading was evaluated. The most recent list of its known populations in the Czech Republic was compiled. These data were subsequently compared, updated and enriched with new locations based on this field monitoring. Its occurrence was evaluated largely in the Vysočina Region, in the area of Velké Meziříčí. As it turned out, the center of the signal crayfish occurrence in the Czech Republic is located really in the area of its original introduction thirty years ago in our country, in the vicinity of the Velké Meziříčí. During that time, signal crayfish have successfully expanded into the surroundings waters, both naturaly (downstream and upstream migration) and with human aid (with restocking fish, direct distribution by the public). It occupied all possible types of habitats, from running waters of the two major rivers Balinka and Oslava to their tributaries creeks of different size and character. It found suitable living conditions also in some ponds, particularly those less intensively farmed. Signal crayfish was recorded in areas, where noble crayfish Astacus astacus is still relativelly widely present, in some place even forming sympatric populations. The work was also focused on epibionts Branchiobdella sp., their presence or absence on caught crayfish. Their occurance was also recorded and evaluated