In recent decades, alien species of gnats (mosquitoes) have increasingly appeared in Europe. Mainly due to the global transport of goods, gnats are passively introduced into new areas; under suitable climatic conditions, new populations can become established. Alien gnat species can be "invasive species" if they are shown to cause changes in ecosystem structure and composition, adversely affect ecosystem services, human economies, and well-being. In the case of alien gnat species in particular, there is a risk that these species could also spread exotic pathogens.

Of particular concern in this regard is the Asian tiger mosquito(Aedes albopictus). This species is a potential vector for over 20 different pathogens such as Chikungunya virus, Dengue virus or Dirofilaria. The tiger mosquito is also highly adaptable and has increasingly spread throughout Europe.

With an Austria-wide monitoring program using ovitraps ("egg traps"), we record the occurrence and spread of alien and potentially invasive gnat species in Austria.

We set ovitraps ("egg-laying traps") at 50 sites throughout Austria, mainly in urban or suburban areas and at locations where alien species may be introduced into the country (e.g., highway rest areas). At each site, traps were placed at multiple locations with the same habitat, spaced approximately 15-100 m apart. We chose locations that were as quiet as possible, shaded, and moist (e.g., in bushes). The traps were checked every week and examined for Gelsen eggs.

In total, we collected 5,691 samples, in 1,099 of these samples (19.3%) we could detect a total of 61,713 Aedes eggs, especially many in Styria.

Four different container-breeding Aedes species were detected: Ae. albopictus, Ae. japonicus, Ae. koreicus and Ae. geniculatus. Genetic species identification was possible in 70.2% of the samples.

The Asian tiger mosquito(Ae. albopictus) was detected at nine sites in five states. Compared to the previous year, it was able to spread significantly in Austria. Especially in Vienna and Graz, this species occurs in large numbers, and it can be assumed that these populations will also overwinter here.

The Japanese bush mosquito(Ae. japonicus) is now found in all provinces of Austria and is particularly widespread in the south.

The Korean bush mosquito(Ae. koreicus) was first detected in Austria in Carinthia in 2019. In 2020, we detected it for the first time in Vienna. Eggs of the native species Ae. geniculatus occurred mainly in south-eastern Austria.

Through this monitoring, new populations of alien Gelsen species can be detected at an early stage. Thus, it is possible to take countermeasures in time and to monitor the development of existing populations. Due to the uniform method used throughout Austria, the data obtained can be used to record spatial and temporal changes in the occurrence of alien gnat species.

The monitoring is carried out in cooperation with the Biological Station Illmitz, Gelsenbekaempfung Leithaauen, Inatura, Landesmuseum Kärnten, Universalmuseum Joanneum (Natural History Museum), University of Innsbruck (Institute of Zoology), University of Salzburg (Department of Biosciences), Verein biologische Gelsenregulierung March-Thaya-Auen, VetmedUni (Institute of Parasitology). and some private persons.

Ovitrap monitoring of alien catfish species in Austria: annual report 2021.