The beluga sturgeon in Russia is the largest fish in the world that can be found in freshwater. This is a very broad question, and difficult to answer without a bit more context. Each of these types of pollution affect individual sturgeons and populations of sturgeon differently. For example, chemical pollution can disrupt the ability of sturgeon to breath which can cause death, or it can disrupt other physiological functions in ways that don't cause death but impair the ability of sturgeon to spawn or reproduce. This sublethal affect leads to a decline in the population over time.
Pollution can also eliminate food for sturgeon.