| dc.description.abstract | In this surveillance programme, environmental DNA (eDNA) monitoring is used for the detection of species specific DNA from spores of Aphanomyces astaci directly from water filtrates. The presence/absence of eDNA from noble crayfish (Astacus astacus) and signal crayfish (Pacifastacus leniusculus) is also determined to supplement the results, and to evaluate the habitat status with higher precision. These analyses are part of the collaboration and coordination with the national surveillance programme for noble crayfish. The main geographic focus of this surveillance programme was on the Halden watercourse and neighbouring risk areas. Other covered geographic areas include the Mosse watercourse, Glomma watercourse, and selected areas in the Eidskog municipality including the Buåa watercourse, the Vrangselva watercourse, and River Finnsrudelva. Detection of noble crayfish eDNA, combined with the absence of eDNA from A. astaci and signal crayfish, substantiate the presence of non-infected noble crayfish, which is the desired habitat status. In total, 59, 48, 21 and 36 water samples were collected from selected sites in the Halden-, Mosse-, Glomma watercourse regions and in the Eidskog region, respectively. Locations for sampling water were strategically selected and focused on both control zones and the risk areas adjacent to crayfish plague control zones. The presence/absence of the three target species was determined simultaneously through screening with species-specific qPCR assays. In 2020, eDNA of A. astaci was only detected in the southern part of Lake Rødnessjøen, and no spread of the pathogen was observed in any of the monitored areas. • In the control zone of the Halden watercourse, A. astaci eDNA was detected in the southern part of Lake Rødenessjøen. Here, the known presence of signal crayfish was also confirmed by positive eDNA detection. Within the control zone, A. astaci was not detected in any other of the stations. All water samples in the risk area of the Halden watercourse region were negative for eDNA from A. astaci and signal crayfish, while most samples were positive for noble crayfish eDNA. • In the Mosse watercourse, no eDNA of A. astaci or signal crayfish was detected, while noble crayfish eDNA was detected upstream of Lake Langen and in the River Tangenelva. • In the Glomma watercourse, there were no detection of eDNA from noble crayfish, nor from signal crayfish or A. astaci. • In Eidskog municipality, all samples were negative for both signal crayfish and A. astaci, while several samples were positive for noble crayfish eDNA in River Vrangselva and River Finnsrudelva. In summary, eDNA from A. astaci was not detected anywhere else than from the signal crayfish location in Lake Rødnessjøen. Frequent detections of noble crayfish eDNA within the regulated A. astaci control zones of the Halden watercourse, Mosse watercourse, and the rivers Vrangselva and Finnsrudelva in Eidskog, suggests the presence of vital noble crayfish populations within A. astaci regulated and restricted zones. This actualize a coordinated plan for defining criteria for documentation of infection freedom. | |
