Answer:
Watershed is a land which receives water from all possible water sources. These regions are composed of land and water. These regions are typically shallower so allows the deposition of water from sources like river, lakes, ponds and other water body and this water gets drained out into a large water body. Virginia's Southern Watershed also acquires water from various sources. The decline in the aquatic species is because of the introduction of invasive species in the watershed obtained from different water sources. These invasive species are competent with native species for resources or they have a predatory instinct therefore, this results in the decline in the native species.