Winter Habitats Used by Largemouth Bass in the Illinois River, a Large River-Floodplain Ecosystem

Abstract

During the winter of 1993–1994, we characterized habitats used by 17 radio‐tagged largemouth bass Micropterus salmoides in La Grange Reach of the Illinois River, a large river–floodplain ecosystem that has been significantly altered from its natural state. Radio‐tagged largemouth bass wintered in backwaters, off‐channel coves, ditches, and marinas from November through February. Electrofishing mean catch rates were higher in the study areas during winter than in other seasons, indicating fish were more concentrated in these areas during winter. Five of nine study areas received thermal inputs from springs or power plants, but water temperatures in all nine areas were warmer than the main channel during winter. Current velocities averaged 2 cm/s in the study areas and 19 cm/s in the main channel. We did not document movement of radio‐tagged fish into the main channel during winter. River levels played a major role in determining the suitability of wintering habitats. When river levels declined, temperatures increased and dissolved oxygen levels decreased in smaller areas with thermal inputs. Thousands of fish, including juvenile and adult largemouth bass, suffered winterkill near one study area when they became trapped in a backwater after river levels declined. As sedimentation continues to fill in backwaters, river levels become ever more critical for maintaining adequate depths and stable water quality for wintering fish. Perhaps the best strategy for providing adequate wintering habitat for Illinois River fish would be a combination of habitat rehabilitation and the maintenance of stable winter river levels by using navigation dams.

Isotopic analysis of three food web theories in constricted and floodplain regions of a large river

“…The annual¯ood period, at least historically, is critical in providing spawning habitat for many riverine ®shes. Reduction in the frequency and magnitude of seasonal¯oods in many temperate large rivers has most likely contributed to the decline of many ®sh species, as evidenced by the record number of many young-of-theyear ®sh produced in response to the 1993¯ood on the upper Mississippi River system (Bhowmik et al 1994;Raibley et al 1997). Seasonal maximum and minimum ows are also important in shaping channel morphology as well as terrestrial and aquatic habitats, particularly backwater areas (Sparks 1995).…”

Spatial gradients in freshwater fish diversity, abundance and current pattern in the Himalayan region of Upper Ganges Basin, India

“…The researchers have used GIS not only in documenting and mapping the biodiversity, but also locating potential fishing grounds, determining fishing patterns, identifying and prioritizing conservation areas, examining aquatic habitat and underlying habitat characteristics for management and restoration, managing resources and many more. Identification of critical habitat is a priority for many fisheries managers, especially those trying to manage large river fisheries resources (Raibley et al 1997). The value of GIS to fisheries professionals is that it allows for 3-D visualization with correct spatial features and attributes for each point.…”

Otolith trace element and stable isotopic compositions differentiate fishes from the Middle Mississippi River, its tributaries, and floodplain lakes

“…Many riverine species are believed to require connectivity of large rivers and floodplain habitats for spawning and larval nursery (Bayley & Li, 1992;Gozlan et al, 1998;Nunn et al, 2007a), foraging (Nunn et al, 2007b), and winter refuge (Knights et al, 1995;Raibley et al, 1997). However, there are currently several hypotheses regarding the primary source habitat (floodplain lakes, tributaries, and river channel) for fishes in large, regulated rivers.…”