1. Dam removal has great potential for restoring rivers and streams, yet limited data exist documenting recovery of associated biota within these systems following removals, especially on larger systems. This study examined the effects of a dam breach on benthic macroinvertebrate and fish assemblages in the Fox River, Illinois, U.S.A. 2. Benthic macroinvertebrates and fish were collected above and below the breached dam and three nearby intact dams for 1 year pre-and 3 years post-breach (2 years of additional pre-breach fish data were obtained from previous surveys). We also examined the effects of the breach on associated habitat by measuring average width, depth, flow rate and bed particle size at each site. 3. Physical habitat at the former impoundment (IMP) became comparable to free-flowing sites (FF) within 1 year of the breach (width and depth decreased, flow rate and bed particle size increased). We also found a strong temporal effect on depth and flow rate at all surveyed sites. 4. Following the breach, relative abundance of Ephemeroptera, Plecoptera and Trichoptera (largely due to hydropsychid caddisflies) increased, whereas relative abundance of Ostracoda decreased, in the former IMP to levels comparable to FF sites. High variation in other metrics (e.g. total taxa, diversity) precluded determination of an effect of the breach on these aspects of the assemblage. However, non-metric multidimensional scaling (NMDS) ordinations indicated that overall macroinvertebrate assemblage structure at the former IMP shifted to a characteristically FF assemblage 2 years following the breach. 5. Total fish taxa and a regional fish index of biotic integrity became more similar in the former IMP to FF sites following the breach. However, other fish metrics (e.g. biomass, diversity, density) did not show a strong response to the breach of the dam. Ordinations of abundance data suggested the fish assemblage only slightly shifted to FF characteristics 3 years after the breach. 6. Effects of the breach to the site immediately below the former dam included minor alterations in habitat (decreased flow rate and increased particle size) and short-term changes in several macroinvertebrate metrics (e.g. decreased assemblage diversity and EPT richness for first post-year), but longer-term alterations in several fish metrics (e.g. 1055 decreased assemblage richness for all three post-years; decreased density for first two postyears). However, NMDS ordinations suggested no change to overall assemblage structure for both macroinvertebrates and fish following the breach at this downstream site. 7. Collectively, our results support the effectiveness of dam removal as a restoration practice for impaired streams and rivers. However, differences in response times of macroinvertebrates and fish coupled with the temporal effect on several habitat variables highlight the need for longer-term studies.
Channel catfish Ictalurus punctatus is a highly mobile species and is known to make extensive seasonal movements in lotic systems. Dams have been suggested to detrimentally affect this species, although abundant channel catfish populations are known to occur in many fragmented rivers. To examine factors that allow channel catfish to persist in impounded rivers, we assessed relative abundance of channel catfish in three impounded and three flowing sites of the Fox River, Illinois, USA. Radiotelemetry was used to determine movement and habitat use patterns of channel catfish among flowing and impounded areas. Relative abundance of channel catfish was consistently higher at flowing sites than at impounded sites during summer. Several radio-tagged channel catfish moved downstream into impounded areas in fall, and all tagged individuals were found in impounded areas during winter. The majority of tagged channel catfish moved upstream into flowing areas during spring. Channel catfish used a wide range of depths (0.28-2.60 m), and were always found in current velocities less than 0.50 m s À1 . They selected most strongly for coarse substrates, but were infrequently found near cover. Although low-head dams restrict the movements of channel catfish, impounded areas appear to provide overwintering habitats that may eliminate the need for seasonal long-distance movements. Small run-of-river impoundments, however, may contain unsuitable conditions for channel catfish during other seasons.
We compared three entrapment gears to determine which method was the most effective for capturing invasive Bighead Carp Hypophthalmichthys nobilis and Silver Carp H. molitrix in terms of numbers of fish captured and labor invested. Gears were deployed concurrently in two backwater lakes of the Illinois River during the summers of 2012–2014. Overall, the nightly catch rates of all fishes, Bighead Carp, and Silver Carp were one to three orders of magnitude greater in pound nets than in either fyke nets or hoop nets. Pound nets collected larger Bighead Carp than hoop nets and fyke nets. Hoop nets were ineffective at catching Asian carp in backwater lakes. Estimation of the effort required to deploy, maintain, and remove each gear type indicated that pound nets were the most cost‐effective gear due to their high catch rates of Asian carp relative to the labor hours invested to collect the catch. Pound nets appear to be an effective means of removing Asian carp in backwater lake habitats of the Illinois River. Received April 20, 2015; accepted September 3, 2015
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