What is the most likely reason for this decline in aquatic species in virginia's southern watershed?

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.

the oxygenated blood then leaves the lungs through pulmonary veins, which return it to the left heart, completing the pulmonary cycle. this blood then enters the left atrium, which pumps it through the mitral valve into the left ventricle. from the left ventricle, the blood passes through the aortic valve to the aorta.

deoxygenated blood leaves through the right ventricle through the pulmonary artery. from the right atrium, the blood is pumped through the tricuspid valve (or right atrioventricular valve), into the right ventricle.