Changes in the Bottom and Shore Fauna of the Middle Illinois River and its Connecting Lakes since 1913-1915 as a Result of the Increase, Southward, of Sewage Pollution

Abstract

The following short account of the principal changes that have occurred both in the composition and abundance of the small bottom-invertebrate fauna of the Illinois River system between Chillicothe and Browning since 1913-1915, these points being respectively 146.5 and 229.5 miles below the mouth of the Chicago River-is based on hauls made in July, August, and September, 1920, with the Petersen quantitative bottom- sampler at seventy-one stations in the river and Peoria Lake between Chillicothe and the head of Grand Island, and at twenty-five stations in five of the more important bottom-land lakes in the neighborhood of Havana.