Invasive silver carp (Hypophthalmichthys molitrix) populations have expanded greatly in the Upper Mississippi River System (UMRS) since their introduction in the early 1970s. We conducted a Chapman-modified, continuous Schnabel mark-recapture population and biomass estimate for silver carp (106-901 mm) in the La Grange reach, Illinois River during 2007-2008. We estimated a total of 328,192 (95% CI 231,226-484,474) silver carp (2,544 per river km 1,792-3,756) comprising 705 (95% CI; 496-1,040) metric tons of biomass (5.5 metric tons per river km 3.8-8.1). Long Term Resource Monitoring Program (LTRMP) data from the La Grange reach showed an exponential increase in silver carp catches since 1998, with an intrinsic rate of increase approaching 84%. In 2008, silver carp comprised about 51% of the total LTRMP annual fish collection. To our knowledge, this large river reach may contain the greatest ambient densities of wild silver carp in the world. Our findings provide a target for reduction efforts and also emphasize the importance of the La Grange reach as a source population for potential expansion of the species to the Laurentian Great Lakes.

25 sites on the Illinois River waterway and one site in Reach 26 of the Mississippi River were electrofished to monitor fish communities. A total of 8,171 fishes representing 62 species (plus one hybrid) from 15 families were collected during 24.68 hours of sampling. Collections made in 2008 indicated continued high catches of gizzard shad, emerald shiner, and bluegill throughout most of the Illinois River waterway. Two new fish species were collected for the first time during project F-101-R. Blackside darter and longnose dace were each collected in the upper river. Single specimens of blackside darter were collected from Bull's Island Bend (RM 241.5) in Starved Rock Reach and Waupecan Island (RM 260.6) in Marseilles Reach. Two specimens of blackside darter were collected from Treat's Island (RM 279.8) in Dresden Reach. Two specimens of longnose dace were also collected at Waupecan Island. Several fish species were collected for the first time within a given river reach in 2008. A single specimen of bighead carp was collected for the first time at Brickhouse Slough on the Mississippi River. A single specimen of redear sunfish was collected at Crater-Willow Islands (RM30.0) in Alton Reach. Two new species were collected in La Grange Reach; a single pumpkinseed was collected at Pekin (RM 155.1) and two specimens of bowfin were collected at Lower Bath Chute (RM 107.1). Two specimens of blackstripe topminnow were collected for the first time in Peoria Reach at Hennepin Island (RM 207.6). Along with blackside darter and longnose dace, two additional fish species were collected in Marseilles Reach. A single specimen of mud darter and two specimens of brook silverside were also collected at Waupecan Island. A single logperch was collected for the first time in Dresden Reach at the Mouth of the DuPage River (RM 277.4). Gizzard shad were the most abundant species collected throughout the waterway in 2008 with 1,802 fish collected comprising 22.1% of the total catch. The sample from Lambie's Boat Harbor (RM 170.3, Peoria Reach) yielded the highest collection of total fish (1,375, 16.8% of the total collection), while the sample from Turkey Island (RM 148.0) produced the lowest total fish (58, 0.07% of the total collection). Fish species richness at sites ranged from 27 at Clark Island (RM 215.3, Peoria Reach) to 12 species at Moore's Towhead (RM 75.3, Alton Reach) and Turkey Island. Fish species richness of the lower, middle, and upper waterway was 24, 49, and 42, respectively. Cyprinid catches continued to remain relatively high in the upper waterway, with bluntnose minnow being the most abundant (429 total fish), making up 17.9% of the total upper waterway catch. Bluntnose minnow, emerald shiner and spotfin shiner together totaled 1,223 fish comprising 51.1% of the upper waterway catch. Important sport fish species such as bluegill, largemouth bass, and channel catfish were collected in all six waterway reaches in 2008. Bluegill catch per unit effort in number of fish collected per hour (CPUE N ) ranged from 169.50 in ...

Altered hydrology resulting from the presence of locks and dams and erosive agricultural land use practices have created conditions that have impacted the growth, distribution, and survival of aquatic vegetation on the Upper Mississippi River System (UMRS). Three inter-related abiotic factors (light transparency, nutrients, and sedimentation) worsened by impoundment and erosive agricultural practices, have played a major role in widespread submersed macrophyte loss in the UMRS. Aquatic vegetation provides food and shelter for biota as well as impacting water quality. Successful efforts to restore aquatic macrophytes on the UMRS have focused on habitat restoration construction projects and water-level management drawdowns. Currently, the status of aquatic vegetation varies within the UMRS, with most of the aquatic vegetation being found between lower Pool 4 (below Lake Pepin) and Pool 13. Although aquatic macrophytes have varied among locations over the past 17 years, an increase in aquatic plants was apparent in 2007 and 2008. Very little research regarding the role of moist soil and emergent vegetation and their responses to ecological factors has occurred within the UMRS. Future research efforts must continue to focus on understanding the ecological and anthropogenic impacts to all aquatic macrophytes within the landscape of one of the largest river systems in the world.

The Illinois River Biological Station monitors fish communities in the Illinois River using two different electrofishing programmes, one using three‐phase alternating current [AC; The Long Term Illinois Fish Population Monitoring Program or long‐term electrofishing (LTEF)] and the other pulsed direct current [DC; The Long Term Resource Monitoring Program (LTRMP)]. In 2001, we replicated three‐phase AC sampling sites with pulsed‐DC electrofishing gear to test for differences between the two collection methods and programmes. Electrofishing runs at each site were standardized by length and time, with 48 samples collected for each gear. Our objective was to test for differences in fish catch rates using total catch, species richness, fish size ranges, and sample composition and structure. Total catch was significantly greater for LTRMP electrofishing (4368 total fish, mean = 91.0 fish per sample) compared with LTEF electrofishing (1423 total fish, mean = 29.6 fish per sample). Species richness also was significantly greater for LTRMP electrofishing (50 total species, mean = 12.9 species per site) compared with LTEF electrofishing (38 total species, mean = 7.9 species per site). Size ranges of fishes, composed of 100‐mm‐length groups, showed higher total catches for the LTRMP within all length groups. Although our analyses suggest that collections from the LTRMP were significantly greater in most instances, a consistent pattern of species composition between the two programmes was not evident. Our results suggest that caution must be taken when attempting to compare fish community composition and structure information between these programmes. Copyright © 2011 John Wiley & Sons, Ltd.