61 contributed to the overharvest of the freshwater mussels in the Fox River and caused their population to decline, resulting in an unhealthier, dirtier Fox River. Decades later, although commercial harvest was terminated and the Clean Water Act was passed in the 1970s, the enforcement of these two protections could not explain why the mussel population still was declining and could not return to its original abundance. Considering that there were other factors contributing to the declining population, a contributor was the fact that the dams in the river caused habitat destruction. The presence of low-head dams in the Fox River degraded the habitat, water quality, and fragmented the river into a series of lentic ecosystems, which caused much of the Fox River main stem to be considered impaired for aquatic life from the sedimentation, changes in stream depth, and increased levels of phosphorus from the habitat degradation.8 These conditions were detrimental to mussels because most freshwater mussels depend on fish to reproduce, where they will attach onto the gills of fish, traveling upstream, for nutrition before dropping, fully formed, onto the river.9 The dams caused 50% of the Fox River to become dam backwater, where the sedimentation, changes in stream depth, and increased levels of phosphorus slowed the river and caused silt to routinely cover a great portion of the river floor. As a result, the dams destroyed the habitat that the mussels used to reproduce in as it is now contrived of uninhabitable conditions for the mussels as well as preventing fish to swim upstream with the mussels for their growth. Alongside the dams, the urbanization of the Fox River watershed has also paralleled the decline in mussel species and species abundance because of habitat destruction and water pollution. The Lower Fox River includes the highest concentration of pulp and paper mills in the world, combined with around 270,000 people living in communities around the river. Before the 1970s, 8 Diane K. Shasteen, Sarah A. Bales, and Alison P. Stodola, “Freshwater Mussels of the Fox River Basin in Illinois,” Technical Report, March 19, 2013, https://hdl.handle.net/2142/45962. 9 Arthur Malm, “The Fox’s Filtering Freshwater Mussels.”
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