During the early 20th century, the Wabash River was home to a vibrant community of river mussels. Due to the high population of mussels in the Wabash, a pearl fishing industry originated around 1900 and operated until 1930. Researchers determine the age of the mussels using similar techniques to tree-ring dating because mussels gain one layer per year. Scientific methods also aide researchers in examining the chemical make-up of the shells which indicates the water quality of the Wabash River. Based on current findings, a random sample of old mussel shells demonstrates that these organisms are between 27 and 50 years of age.