Spatial and temporal differences in fish assemblages in the Sangamon River, Illinois: Methods for community comparisons and documentation of species' range expansion

Abstract

Anthropogenic disturbance has been recognized as having adverse effects on native flora and fauna in an environment. One such disturbance that has received increasing attention in recent years is the effects of water altering structures such as reservoirs, dams, dykes, and levees. For the past 6 years, Eastern Illinois University has conducted an intensive sampling program in an effort to document spatial and temporal heterogeneity of an 8.5 km reach of the Sangamon River beginning just below Lake Decatur Dam in Decatur, Illinois. My objective has been to characterize stream habitat and to assess differences in stream fish assemblages above versus below a municipal wastewater treatment plant. Thirteen sample locations were chosen and sampled for fish, using standard seining techniques, during the summers of 1998, and 2001 through 2005. I compared reaches by both ANOVA of IBI scores and measures of diversity as well as multidimensional scaling of the entire fish assemblage present. I found that fish assemblages in these reaches are not distinct based on the IBI or Shannon-Wiener index of diversity because these measures were not sensitive enough to assemblage changes in this region. The MDS revealed distinct assemblages between the reaches as well as among most of the sampling years. The MDS also allowed me to analyze species level trends in the assemblage, and in doing so I found that the red shiner (non-native) played a key role in community disparities. The appearance of this species coincided with a total extinction of the redfin shiner, and altered community dynamics.

Date of Award	2006
Original language	American English
Awarding Institution	Eastern Illinois University
Supervisor	Robert Fischer (Supervisor)