The researchers studied fish communities in a stream in Slovakia to see how different factors affect where fish species live. They found that the distance from the source of the stream, depth, and slope of the site influence the types of fish found there. Factors like depth and vegetation cover also play a role. The study suggests that brown trout and grayling are not native to the stream, but they thrive there due to favorable conditions. The stream provides a good environment for fish, with varying conditions that support different species.