Historical Changes in Fish Assemblage Structure in Midwestern Nonwadeable Rivers

Abstract

Historical change in fish assemblage structure was evaluated in the mainstems of the Des Moines, Iowa, Cedar, Wapsipinicon, and Maquoketa rivers, in Iowa. Fish occurrence data were compared in each river between historical and recent time periods to characterize temporal changes among 126 species distributions and assess spatiotemporal patterns in faunal similarity. A resampling procedure was used to estimate species occurrences in rivers during each assessment period and changes in species occurrence were summarized. Spatiotemporal shifts in species composition were analyzed at the river and river section scale using cluster analysis, pairwise Jaccard's dissimilarities, and analysis of multivariate beta dispersion. The majority of species exhibited either increases or declines in distribution in all rivers with the exception of several "unknown" or inconclusive trends exhibited by species in the Maquoketa River. Cluster analysis identified temporal patterns of similarity among fish assemblages in the Des Moines, Cedar, and Iowa rivers within the historical and recent assessment period indicating a significant change in species composition. Prominent declines of backwater species with phytophilic spawning strategies contributed to assemblage changes occurring across river systems. KeywordsIowa, fish assemblages, spawning strategies, rivers, animal ecology RightsWorks produced by employees of the U.S. Government as part of their official duties are not copyrighted within the U.S. The content of this document is not copyrighted. ABSTRACT.-Historical change in fish assemblage structure was evaluated in the mainstems of the Des Moines, Iowa, Cedar, Wapsipinicon, and Maquoketa rivers, in Iowa. Fish occurrence data were compared in each river between historical and recent time periods to characterize temporal changes among 126 species distributions and assess spatiotemporal patterns in faunal similarity. A resampling procedure was used to estimate species occurrences in rivers during each assessment period and changes in species occurrence were summarized. Spatiotemporal shifts in species composition were analyzed at the river and river section scale using cluster analysis, pairwise Jaccard's dissimilarities, and analysis of multivariate beta dispersion. The majority of species exhibited either increases or declines in distribution in all rivers with the exception of several ''unknown'' or inconclusive trends exhibited by species in the Maquoketa River. Cluster analysis identified temporal patterns of similarity among fish assemblages in the Des Moines, Cedar, and Iowa rivers within the historical and recent assessment period indicating a significant change in species composition. Prominent declines of backwater species with phytophilic spawning strategies contributed to assemblage changes occurring across river systems.

Identifying and quantifying environmental thresholds for ecological shifts in a large semi-regulated river

“…This result supports recent research documenting ecological shifts in the opposite direction (from clear to turbid states) in which a decline in backwater specialists was observed in agriculturally impacted Midwestern rivers (Parks et al 2014). TSS concentration was lower, and vegetation coverage within Pool 8 was greater, than the highly impacted rivers in Iowa, USA, studied by Parks et al (2014). It seems likely that the expansion of vegetation beds in Pool 8 has increased areas of low water velocity within the pool, and is a possible reason for the decline in limnorheophils (Sand-Jensen 1998).…”

“…This is consistent with the results of many studies demonstrating a significant positive relationship between common carp mass (non-native to North America) and TSS concentration (Meijer et al 1989;Meijer et al 1990;Havens 1991;Breukelaar et al 1994). Conversely, many studies have shown an increase in native fish biomass as TSS is reduced and vegetation coverage increases (Grift 2001;Zambrano et al 2001;Parks et al 2014). Because TSS had such a pronounced effect on the dominance between native and non-native indexed fish mass, I expect that TSS reductions will be critical to native fish conservation in the upper impounded Mississippi River.…”

“…The increase in fish with phytophilic spawning strategies is encouraging and suggests that the reduction of TSS can contribute greatly to the restoration of ecological structure of North American rivers affected by agriculture. My results again corroborate those of Parks et al (2014) who noted substantial declines in fish with phytophilic spawning strategies in Iowa, USA. Rivers as flow regimes were altered, water quality degraded and river corridors were fragmented following the onset of intensive row crop agriculture.…”

“…The positive relationship between aquatic vegetation and visual predator species like largemouth bass and northern pike is well known, but an understanding of the ecological importance of formerly reviled fishes such as gars and bowfin has only recently come to light (Scarnecchia 1992). Having the full complement of carnivorous fishes is critical to ecosystem function, especially for controlling recruitment of ecosystem generalists of the invertivore-detritivore guild, with the most prominent of this group being the common carp (Parks et al 2014).…”

“…Widespread landscape disturbance, resulting in increased sediment loads, has been identified as driving declines in SAV abundance resulting in declines in backwater specialists and predators with phytophilic spawning strategies (Parks et al 2014). Relatively clear, vegetated systems tend to be dominated by visual predators such as yellow perch (Perca flavescens), northern pike (Esox lucious) and largemouth bass (Micropterus salmoides) (Kipling 1983;Killgore et al 1989).…”