Effect of a Recently Completed Habitat Rehabilitation and Enhancement Project on Fish Abundance in La Grange Pool of the Illinois River Using Long Term Resource Monitoring Program Data

Abstract : The Long Term Resource Monitoring Program (LTRMP) fish component monitors fish communities to test for changes in abundances and species composition in six regional trend areas of the Upper Mississippi River System. Using these data, we evaluated the ability of the LTRMP to detect changes in the fish community as a consequence of a habitat-enhancement project in La Grange Pool of the Illinois River. In 1996, initial phases of the Chautauqua National Wildlife Refuge Habitat Rehabilitation and Enhancement Project (HREP) south cell construction were completed with the goal of improving fish habitat in the pool. That year, an estimated 46 million fish representing 34 species were produced and discharged from the south cell of Lake Chautauqua. Whereas this response may indicate that the south cell serves as a spawning and nursery area for many fish species, no studies have tested for recruitment to the river fish community. We used geographic information system coverage at three spatial scales in the main-channel and side-channel strata to illustrate potential fish-community responses. At these spatial scales (local 1 river mile [RM], regional ~10 RMs, and pool wide 80 RMs), we assessed fish catch-per-unit-effort (CPUE) data collected from mini-fyke net and day electrofishing among pre- (1993 1995) and post-HREP (1996 2005) periods of the Chautauqua National Wildlife Refuge HREP. Analysis of Similarity results demonstrated no significant differences among periods in fish CPUE (P > 0.05). Our results may indicate that (1) the LTRMP sampling design lacked sufficient statistical power to detect effects of the HREP, (2) the LTRMP sampling design lacked the spatial and temporal resolution to detect effects, (3) the Lake Chautauqua HREP has not been established long enough to detect long-term trends in fish production, or (4) the HREP had no effect on fish recruitment to the Illinois River.