The noble crayfish (Astacus astacus) is critically endangered in Sweden. This is mainly due to the crayfish plague (Aphanomyces astaci), a lethal disease that, among other things, can be spread through the stocking of fish from contaminated water or contaminated fishing gear. The largest single propagation path is the illegal introduction of infected signal crayfish (Pacifastacus leniusculus). A conservation measure for crayfish is to re-introduce it to where it has a chance to survive, though a sustainable, locally regulated fishing can also serve as an indirect protection for the species. When the local inhabitants are allowed to keep their fishing culture and when fishing is acceptable, the incentive for illegal stocking of signal crayfish is low. However, it is important to avoid overfishing because the recovery, especially in the northern regions, can take several years. Therefore, it is important to know how crayfish respond long-term to fishing and environmental factors. Crayfish populations became extinct in the River Ljungan for unknown reasons in 1999. The water flow of the river has been used for activities such as fishing, timber transport and hydroelectric power since the 1500s, and the noble crayfish has been part of the fauna since the last century. The River Ljungan was known as one of Sweden's best fishing areas for crayfish and fishing became an important part of the local tradition. When the crayfish populations became extinct, a reintroduction program was a natural step, and crayfish are nowadays re-established in the river. From 1963 to 1990 the Swedish Board of Fisheries collected data from crayfish fishing in the River Ljungan to determine the economic damage to fishery owners caused by the construction of a power plant. After each season the fishermen reported the catch. In this thesis, the data was used to investigate which factors influence the long-term size of the crayfish catch and how the crayfish catches were affected by the power plant building. After re-introduction of the crayfish to the River Ljungan, the local fishermen monitored the population development in a simple, standardized way. To examine the validity of their measurements and to investigate the body growth of the individuals, a capture-recapture technique with a permanent marking of the crayfish was used. The crayfish catches were primarily impacted by the previous years' catch size, and a large catch the previous year resulted in a reduced catch the following year. A mild winter climate (NAO-index > -0.7) six years before the catch implied a large catch, whereas a high water flow during the autumn or spring (>95m3s-1) two years before the catch, implied a poor catch. Major habitat changes in the form of greatly reduced water flow (~90%) were negative for crayfish catches. The standardized method of fishing used by the local fishermen to monitor the development of the crayfish population was precise enough to detect population trends and this method can therefore be recommended to monitor future re-introductions of crayfish. Although the River Ljungan is located at the northern edge of the species' range, noble crayfish in the river presently have a body growth rate that is close to the maximum measured for crayfish (8 mm/moult for females and 10 mm/moult for males). Based on the results, the most important advice for sustainable fisheries in Ljungan and other northern rivers is to: Monitor the population trends, NAO-index and water flow in May and October.  Use the results from the monitoring to determine the number of allowed fishing days and traps. Collect data about the catch size and efforts from legal fishing and use it to evaluate the sustainability of the fishing. Enhance the buildup of the harvestable cohort by -saving reproductive females -introduce a size limit of 10 cm -provide proper shelters for the non-harvestable cohort. / Flodkräftan (Astacus astacus) är akut hotad i Sverige främst på grund av kräftpest (Aphanomyces astaci). Kräftpest är en dödlig sjukdom som bland annat kan spridas vid fiskutsättningar från smittade vatten eller med smittade fiskeredskap. Den enskilt största spridningsvägen är illegala introduktioner av smittade signalkräftor (Pacifastacus leniusculus). En bevarandeåtgärd för flodkräfta är att återintroducera den till lokaler där den har chans att överleva, men ett hållbart fiske med lokal styrning kan också fungera som ett indirekt skydd för arten. När lokalbefolkning tillåts att behålla sin fiskekultur och fisket är bra, blir incitamentet för illegal inplantering av signalkräfta lågt. Men det är viktigt att undvika överfiske då återhämtning, speciellt i nordlig miljö kan ta åtskilliga år. Därför är det betydelsefullt att veta hur flodkräftan svarar på fiske och omgivningsfaktorer i det långa loppet. Flodkräftbeståndet dog, av okänd anledning, ut i Ljungan 1999. I Ljungans flöde har det fiskats, flottats timmer och utvunnits vattenkraft etc. sedan 1600-talet och under det senaste århundradet har flodkräftan varit en del av Ljungans fauna. På sin tid var det en av Sveriges bästa lokaler för flodkräfta. Kräftfisket blev en viktig del av den lokala traditionen, så när kräftbeståndet dog ut var återintroduktion en självklarhet och flodkräftan har åter sin hemvist i älven. Under perioden 1963 till och med 1990 samlade Fiskeriverket in data från kräftfisket i Ljungan för att fastställa den ekonomiska skadan som fiskerättsägarna åsamkats i samband med ett kraftverksbygge. Efter varje säsong fick fiskarna rapportera hur fisket gått. I den här avhandlingen, har det materialet använts för att undersöka vilka faktorer som påverkar kräftfångstens storlek på lång sikt och hur kräftfångsterna påverkades av kraftverksutbyggnaden. Efter återintroduktionen av flodkräfta till Ljungan mättes beståndsutvecklingen på ett enkelt, men standardiserat sätt av de lokala fiskevårdsområdena. För att undersöka validiteten av deras mätningar och hur kräftornas individuella utveckling fortskred, användes fångst- och återfångstteknik, med permanent märkning av kräftorna. Kräftfångsternas storlek påverkades främst av tidigare års fångststorlek; en stor fångst föregående år innebar minskad fångst följande år. Ett milt vinterklimat (NAO-index > -0.7) sex år före fångst innebar bättre fångster, medan höga vattenflöden höst och vår (>95m3s-1) två år före fångsttillfället innebar sämre fångst. Större habitatförändringar i form av kraftigt reducerade vattenflöden (~90%) var negativt för kräftfångsterna. Den standardiserade metoden som fiskevårdsområdena använt för att mäta beståndsutvecklingen var tillräckligt precis för att påvisa populationsutvecklingen och kan därför rekommenderas också för uppföljning av andra återintroduktioner av flodkräfta. Trots att Ljungan ligger i norra kanten av flodkräftans utbredningsområde har flodkräftorna i Ljungan för närvarande en kroppstillväxt som är nära den maximala som uppmätts för flodkräfta (8 mm/ömsning för honor och 10 mm/ömsning för hannar). Utifrån resultaten är de viktigaste råden för ett hållbart fiske i Ljungan och andra nordliga vattendrag att: Övervaka kräftstammens utveckling, NAO-index samt vattenflöde i maj och oktober.  Använda resultaten från övervakningen för att bestämma antalet tillåtna fiskedagar och burar. Samla in data om fångststorlek och hur många burnätter som faktiskt gjordes under säsongen. Använda data för att utvärdera fiskets hållbarhet. Stärka uppbyggnaden av den fångstbara storleken genom att -spara reproduktiva honor -införa en storleksgräns på 10 cm -tillse att det finns gömslen för kräftor av icke-fångstbar storlek.

Activity of noble crayfish (Astacus astacus) and spiny-cheek crayfish (Orconectes limosus) under the laboratory coditions University of South Bohemia České Budějovice - Faculty of Agriculture, Department of Fisheries Author: Martin Musil Contact: mue.@seznam.cz Abstract: Some authors point out, that the American species are more activated than European during the day. Noble crayfish (Astacus astacus L.) is the night animal. Spiny-cheek crayfish (Orconectes limosus Raf.) is the most agresive species with more activity during the day, whose is of itself ecologic and reproductions characteristic typical r{--}strategist. And over than above it is a vector of crayfish plague. Objective of this study was the observe the daily and noctural of both species, the influence of fish predators and murmurs of agresivity. The bulk of this work was in ethologic laboratory with using videotechnic in control conditions and directed lightregimen. The findings see the big diference between species, that the spiny-cheek crayfish is more activated that the noble crayfish (51,4%{$\pm$}4,33 of the 24 hour activity) with slight diference between the day and night. Someones of the subjects don´t look for the cover during the experiment, it were mainly the females, whose activity were better than the male. Noble crayfish embodied low aktivity (15,1%{$\pm$}8,22 of the 24 hour activity) with more highly diference between the day and night and with slight diference between the sex. The inherence of the fish predator have had slight influence on the both species, rather sometimes take on the crayfish attention. The agresivity of the both is at least comparable, so it isn´t clear, that the spiny-cheek crayfish would be more successful in proximate competetion without the infection of crayfish plague.

The crayfish plague pathogen, Aphanomyces astaci, is one of the most serious threats to European indigenous crayfish species, e.g., the noble crayfish (Astacus astacus). The only way to protect susceptible crayfish species from the disease is to prevent the dispersion of the pathogen to their populations. One of the most important sources of the crayfish plague pathogen in Central Europe is the spiny-cheek crayfish (Orconectes limosus), a species of North American origin, which can carry the parasite in its cuticle for years. Some literature sources claimed that the pathogen dispersion from the American vectors is restricted to periods of moulting or to the time before and after the crayfish death. However, experimental evidence for such hypotheses was lacking. The main aim of my thesis was to test these predictions, and the alternative scenario that the crayfish plague pathogen can be transmitted from the infected spiny-cheek crayfish also in other periods. For this purpose, experiments were set up to investigate A. astaci transmission from infected spiny-cheek crayfish to non-infected spiny-cheek or noble crayfish. As expected, the pathogen was transmitted to noble crayfish much more easily than to the uninfected American host. Nevertheless, we succeeded in the pathogen transmission also among spiny-cheek...

On the northern shores of the recreated lake apal an isthmus protrudes spanning east and west. A road runs along the isthmus and from its center a leisure and culture-center spans out over the water. The isthmus protects the surrounding countryside from flooding during extreme rainfall as it is predicted by MSB. There is an outlet for water connecting lake Hjälmaren with lake Mälaren containing a concrete obstacle for wandering crayfish.The Center is dedicated to the restored lake and its environmental benefits and to the Noble Crayfish domestic in Sweden but now faced with extinction due to the invasive Signal crayfish. The center follows the gentle curvature of the isthmus, half of it resting on the isthmus the other half protruding out over the water. 896 thin piles made of reinforced concrete carries the building with rests on a concrete slab. Large glulam frames and CLT beams makes out the carrying construction of the building. A long room whose width expands and collapses during its course spanns the entire length of the building and it too follows the curvature of the isthmus. No doors lead directly out to the long room, all room-exits go in an east and west direction. Large windows overlook the lake from the central restaurant, dedicated to the homegrown crayfish. The interior walls, roof and floor is made upp by wooden planks following the curvature of the Center. The glulam frames are, although clad because of the climatic surrounding, visible on the buildings exterior walls and roof like ribbs. The roof and ribbs are matt black and the walls are falu-red. Public spaces look out over the lake while the interior service rooms face north to the road. Main entrances and exits are on the eastern and western side, while cargo-loading is located on the northern side accessible from the road. / Längs den återskapade Apalsjöns nord östra strand ringlar ett näs i ost västlig rikting. På näsets norra sida löper en väg och söder om vägen samt ut över vattnet sträcker sig ett hus vars långsmala kropp följer näsets konturer. Näset skapar en vattenbarriär och skyddar den omkringliggande åkermarken från de översvämningar som beskrivs på MSB´s katastrofkartor vid framtida extremväder samtidigt som vattenutsläppet garanterar fortsatt sammanbindning av Hjälmaren och Mälaren. Ett vandringshinder i betong för signalkräftor finns i vattenutsläppet. Det långsmala huset är ett Folketshusdistriktet och Naturum, dedikerat till den återskapade sjön och till den inhemska svenska flodkräftan. Flodkräftan, snart stöd i vilt tillstånd, odlas i anslutning till huset i dammar på näset, för konsumtion i restaurangen samt försäljning. Kräftyngel odlas för försäljning till omkringliggande lantbrukare för odling i egna dammar. 896 20•20 betongpelare bär upp betongplattan och utgör husets grund. Stora ramar i limträ, takbjälkar i kl-trä och kl-vägskivor utgör husets huvudsakliga bärande konstruktion. Limträramarna är synliga i husets fasad. Inklädda till skydd mot vädret spänner dom över byggnaden som revben. Taket och "revbenen" är mattsvarta och ytterväggarna målade faluröda. Halva huset vilar på näset och halva skjuter ut över sjöytan. Husets södra del utgörs av publika rum med generösa fönster som blickar ut över sjön. Den norra delen av byggnaden består av interna personalutrymmen, toaletter, teknikrum, vaktmästeri etc. Ett långt rum löper genom hela husets längd i öst-västlig riktning, ömsom ökandes i bredd, ömsom avsmalnande. Inga dörrar öppnas direkt mot detta rum utan alla dörrar öppnas åt öst eller väst. De publika ingångarna till huset finns på östra och västra kortsidorna, inläsning sker på nordsidan från vägen.

The most widespread of invasive crayfish in the Czech Republic is the spiny-cheek crayfish (Orconectes limosus). It is a major disease carrier of crayfish plague, caused by the pathogen Aphanomyces astaci. The infection is lethal to European native species of crayfish. Transmission of this disease is usually associated with the spread of crayfish, which is dependent on their movement. The main aim of this work was to evaluate the differences in crayfish migratory activity in the Pšovka brook among seasons, and assess the factors that may affect it, by the use of radiotelemetry and trapping. We tested the hypothesis that crayfish use brook in the period from spring to autumn and then return back into a pond to overwinter. Furthermore, we evaluated how far from the pond crayfish migrate, and whether there is any relationship between migration and the season or water temperature. The results demonstrate that the activity varies among seasons (being strongly affected by breeding season) but in most studied periods did not significantly depend on water temperature. According to our monitoring, the spiny-cheek crayfish does not spread substantially to upstream parts of the Pšovka. Seasonal migration between the pond and the brook was monitored using two-way flow-through traps installed at the mouth of...

This thesis is composed of two parts - research part, focused on field research of occurence and abundance of the Stone Crayfish and the Noble Crayfish in the basin of Zákolanský stream, and a pedagogical part, project Crayfish in the Czech Republic and their protection, aimed for grammar school students. The literature outline summarizes contemporary knowledge about all five species of crayfish in the Czech Republic. Our native species are the Stone Crayfish (Austropotamobius torrentium) and Noble Crayfish (Astacus astacus). The non-native are Narrow-clawed Crayfish (Astacus leptodactylus), Spiny-cheek Crayfish (Orconectes limosus) and Signal Crayfish (Pacifastacus leniusculus). Aside from the chapters concerning the particular species and their determination, the literature outline also contains general information about the life and endangerment of crayfish. I have conducted the field research from April to September 2009. I also noted and evaluated the environmental conditions of the crayfish habitats. Based on the adjusted AOPK ČR methodology, I selected eight 100-meter long brook-sections of the Europe-important locality of Zákolanský stream, with the previously confirmed occurrence of crayfish. From the eight sections, I found crayfish only in three. All the captured specimens were of the...

This thesis deals with monitoring the occurrence of crayfish in selected river basins in the western Bohemia, considering the human impact on freshwater ecosystems and his influence on crayfish and other aquatic organisms. The selected river basin territory was Úhlava, Úslava and Otava. In the localities, numerical and species-wise representation of crayfish was monitored by finding data from the Agency for Nature Conservation and Landscape of Czech Republic database. The flow and environment characteristics were also monitored. This thesis focuses on water quality in streams of selected major river basins, Úhlava, Úslava and Otava rivers in the period from 2006 to 2011. Results of the findings show a sympatric occurrence of original species, stone crayfish (Austropotamobius torrentium), noble crayfish (Astacus astacus) and part of the original danube crayfish (Astacus leptodactylus) with invasively spreading species of spiny-cheek crayfish (Orconectes limosus) and signal crayfish (Pacifastacus leniusculus). With respect to this fact, the sensitivity of spiny-cheek crayfish (Orconectes limosus) and signal crayfish (Pacifastacus leniusculus) are evaluated in a form of own test results on acute toxicity. The thesis compared current results of occurrence and the protection of crayfish in the Czech Republic and abroad. The conclusion of this thesis is a proposal of a freshwater biomonitoring system, using the crayfish.