Catfish Population Characteristics among River Segments with Altered Fluvial Geomorphic Conditions in the Missouri River, Nebraska, USA

Abstract

Alteration of river systems around the world has created novel environments that have been fragmented, homogenized, or transformed from their natural state, thus posing challenges for understanding how fish populations function. The Missouri River has undergone significant alteration through reservoir construction and channelization. Channel Catfish Ictalurus punctatus and Flathead Catfish Pylodictis olivaris both reside in various fragmented sections of the river, and there is a substantial gap in knowledge of how catfishes synchronously function in this modified system. From 2009 to 2018, we assessed catfishes with baited hoop nets and low‐frequency electrofishing among four different areas: upper and lower unchannelized segments and upper and lower channelized segments. Differences in population demographics and dynamics occurred for both species among segments. Both the highest and lowest relative abundances for Channel Catfish occurred in channelized segments, and Flathead Catfish relative abundance was lowest in both unchannelized segments. Subadult growth rates for both catfish species were greater in channelized segments. Channel Catfish mortality was highest in channelized segments, which was consistent with the maximum ages found in channelized (age 9) versus unchannelized (age 15) segments. High‐flow events in 2010 and 2011 led to an increase in recruitment, but populations declined in subsequent years. This long‐term assessment revealed spatial and temporal differences in population dynamics among varying levels of anthropogenic alteration. Our study illustrates how river modification and extreme climatological events may impact and structure catfish populations. These data provide a basis for assessing catfish throughout the Missouri River system and offer insight into how catfish populations in other altered large‐river systems might function.

Two Decades of Advancement in Flathead Catfish Research

“…2012; Hamel et al. 2021). Although the Flathead Catfish is a freshwater species, these fish can tolerate salinity levels up to 11‰, making them tolerant of estuarine habitat (Bringolf et al.…”

“…Although many fish are sedentary for portions of the year, recent studies (Travnichek 2004; Hamel et al. 2021) suggest that annual movement is sufficient to necessitate management of populations at the riverwide level.…”

“…2006; Makinster and Paukert 2008; Hamel et al. 2021; Schall and Lucchesi 2021), from 0.11 to 0.40 in reservoirs (Winkelman 2011; Stubbs et al. 2015; Lucchesi et al.…”

“…Only two studies evaluated habitat selection in reservoir habitat rather than in rivers (Weller and Winter 2001;Vrtiska et al 2003), but habitat selection in reservoirs appears similar to that described for rivers (primarily rocky habitat, with some use of wood). Reservoir Flathead Catfish populations exhibit high resiliency even after unfavorable riverine hydrologic conditions (Sakaris and Irwin 2010), and flooding can provide additional suitable habitat for juveniles, thereby increasing recruitment during highwater years (Stanley et al 2012;Hamel et al 2021). Although the Flathead Catfish is a freshwater species, these fish can tolerate salinity levels up to 11‰, making them tolerant of estuarine habitat (Bringolf et al 2005).…”

“…The degree of urbanization affects the growth and abundance of Flathead Catfish. Flathead Catfish grow faster in areas of low urbanization (i.e., areas with mature riparian habitat) and have a higher relative abundance in areas with agricultural land use than urban use (urban aquatic habitat is often characterized by dredging, channelization, and degraded riparian zones; Paukert and Makinster 2009;Hamel et al 2021). Agricultural areas often have higher nutrient loading rates that increase the productivity of aquatic habitats, which in turn may increase prey abundance for Flathead Catfish.…”