Graduate Program

Environmental Biology

Degree Name

Master of Science (MS)

Semester of Degree Completion


Thesis Director

Leonard Durham


The repopulation of stream fishes was studied from 17 May 1979 to 25 October 1979 following a major kill (100% mortality) caused by nitrogen fertilizer pollution in Riley Creek, Coles County, Illinois. The extent of recovery was determined by comparing post-kill collections with pre-kill survey data that was collected on 25 October 1978.

Repopulation began six days after the abatement of the pollution source. It is suggested that the initial source of repopulation was from the nearest undamaged tributary. The first three reinhabitants in order of appearence were: stonerollers (Campostoma anomalum); creek chubs (Semotilus atromaculatus); and creek chubsuckers (Erimyzon oblongus). At the end of the study period, 21 of the original 27 species had reentered the sampling area. The major changes from pre- to post-kill periods were an increase in total number of individuals, a decrease in overall total weight and a decrease in mean weight per individual. The increase in total number and the decrease in overall total weight was primarily due to a tremendous increase in abundance of small cyprinids and a decrease in abundance of large white suckers (Catostomus commersoni), gizzard shad (Dorosoma cepedianum) and bluegill (Lepomis macrochirus). Repopulation was accomplished primarily by young-of-the-year or immature individuals which accounted for the decrease in mean weight per individual.

Several biotic and abiotic factors are suggested and discussed as having influenced the rate of repopulation. These include: (1) severity and duration of the kill, (2) season of the year, which may manifest itself in stream flow and migrations and breeding of fishes, (3) presence of nearby undamaged areas, (4) evolutionary adaptations of the fishes involved and, (5) predation and interspecific competition of ingressing fish.

The complex of these factors was in general considered favorable and aided in the relatively rapid recovery of the habitat and the subsequent early ingression and reestablishment of substantial fish populations.