Assessing the range of newly established invasive species in rivers using probabilistic methods

Data on the presence of invasive species are often scarce, especially during the initial period following their introduction, when population abundance and species detectability are both still very low. In such cases, sporadic sightings in their newly occupied territory are often the only available information about their presence and distribution. Here, we demonstrate the potential of using probabilistic models for the assessment of the distribution of newly established invasive species in rivers, based on their sighting records. We have applied Solow's equation to the sighting record of the Amur sleeper (Perccottus glenii) in the Danube River, to assess the probable range of its population. The method applied indicated that, at the time when the sightings have been made (2003-2008), the Amur sleeper population in the Danube most probably extended between the 704.5 and 1,178.5 river km, while it was highly improbable (P < 0.05) that it was present downstream from the 606 river km or upstream from the 1,277 river km. The application of this approach has, however, to be tested further on a larger number of scenarios and case studies in order to evaluate its reliability. What this method lacks in complexity, compared to more advanced species distribution assessments, it makes up by its ability to be easily used and quickly applied for preliminary assessments of the ranges of riverine species. As a result, the proposed approach might be of interest for scientists and managers dealing with invasive species.