AVONDALE, Pa., April 21 (UPI) -- A pair of researchers were trying to measure the effects of crayfish in small stream ecosystems. During their experiments, they happened upon a surprising result -- one that suggests the presence of crayfish is beneficial to a stream's health.
Scientists created a series of mesh enclosures in Valley Creek, a tributary of the Schuylkill River outside Philadelphia that has been degraded by urbanization. In some enclosures, the researchers deposited crayfish. Others were left crayfish-free.