Dating back to the 1600s, Onondaga Lake has always shown reports of a cold-water system supporting certain types of fish. Around the late 1800s, degradation occurred and the fish that once thrived in the lake, such as the American eel, Atlantic Salmon and Whitefish declined. The decrease in population was resulting from the increase in temperatures because of severe pollution and human activities taking place. Even though the species are starting to gain numbers in this lake once again, the evidence shows that pollution had a direct impact on the fish that once inhabited this environment.