Effects of Lowhead Dams on Riffle‐Dwelling Fishes and Macroinvertebrates in a Midwestern River

Abstract

Many studies have assessed the effects of large dams on fishes and macroinvertebrates, but few have examined the effects of lowhead dams. We sampled fishes, macroinvertebrates, habitat, and physicochemistry monthly from November 2000 to October 2001 at eight gravel bar sites centered around two lowhead dams on the Neosho River, Kansas. Sites included a reference site and a treatment site both upstream and downstream from each dam. Multivariate analysis of variance indicated that habitat, but not physicochemistry, varied immediately upstream and downstream from the dams, with resultant effects on macroinvertebrate and fish assemblages. Compared with reference sites, upstream treatment sites were deeper and had lower velocities and downstream treatment sites were shallower and had higher velocities; both upstream and downstream treatment sites had greater substrate compaction than reference sites. Macroinvertebrate richness did not differ among site types, but abundance was lowest at downstream treatment sites and evenness was lowest at upstream treatment sites. Fish species richness did not differ among site types, but abundance was highest at downstream reference sites and evenness was highest at upstream sites. The abundance of some benthic fishes was influenced by the dams, including that of the Neosho madtom Noturus placidus, which was lowest immediately upstream and downstream from dams, and those of the suckermouth minnow Phenacobius mirabilis, orangethroat darter Etheostoma spectabile, and slenderhead darter Percina phoxocephala, which were highest in downstream treatment sites. Although limited to one system during a 1‐year period, this study suggests that the effects of lowhead dams on fishes, macroinvertebrates, and habitat are similar to those reported for larger dams, providing important considerations for riverine ecosystem conservation efforts.

Influences of low-head dams on the fish assemblages in the headwater streams of the Qingyi watershed, China

“…However, our results showed that fish abundance and density of the sites immediately upper dams were lower than those of the two reference sites. This is similar with the pattern observed by Tiemann et al (2004), who revealed that low-head dams resulted in the significant decrease in fish abundance and density, not species richness, in the impoundment areas. Based on the linear regression analysis, we found the negative correlation between wetted width and fish abundance and density.…”

“…Undoubtedly, the effects of low-head dams are smaller and more localized than those of large dams (Gillette et al 2005). By impoundment upstream, low-head dams alter the habitat characteristics in the stream segments immediately upstream of dams, such as the increase in channel width and water depth while the decrease in current velocity and substrate size (Dodd et al 2003;Tiemann et al 2004Tiemann et al , 2005Gillette et al 2005;Santucci et al 2005). In our results, the similar changes were observed for wetted with, water depth and current velocity, which was associated with the effects of the impoundment by low-head dams.…”

“…In our results, the similar changes were observed for wetted with, water depth and current velocity, which was associated with the effects of the impoundment by low-head dams. In addition, by plunge downstream, the surface release of low-head dams scours channel bed, causing the shallower and faster-flowing habitat conditions in the segments downstream of dams (Dodd et al 2003;Tiemann et al 2004). However, our results suggested that the site immediately below dams was characterized by relatively deeper water and slower flow.…”

“…We selected sites immediately downstream of dams, which suggested that these sites were located in the plunge areas by the surface release of low-head dams. But their sites, approximately 0.1 km from dams downstream, excluded the plunge areas (Dodd et al 2003;Tiemann et al 2004). …”

“…In addition to the block of fish passage, some researchers have examined how low-head dams affect fish assemblages by altering or modifying local habitat. Tiemann et al (2004) revealed that low-head dams altered water depth and current velocity in segments adjacent to dams, resulting in the local variations in fish abundance and density with an exception of fish species richness. Whereas, Dodd et al (2003) observed that fish species richness peaked just below low-head dams, which is due to that these dams block fish movement upstream.…”