Historically, the commercial harvest of mussel shells in Kansas rivers has varied markedly in response to market demand. Peak mussel harvests accompanied the high shell demands and market values that occurred in the early 1970s and 1990s. The Threeridge Amblema plicata was the most heavily harvested species during both periods. Recent quantitative mussel surveys indicate a decline in A. plicata population density in rivers subjected to commercial harvest; however populations in other rivers remain robust. In 2003, the Kansas Department of Wildlife and Parks declared a ten-year moratorium on commercial shell harvest to assess the effects of this activity on mussel populations.