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Bigheaded carp (Hypophthalmichthys spp.) occur throughout much of the Mississippi Basin, USA. Efforts to control the spread of these invasive species require information on their spatial ecology, though sampling is hindered by their broad extent, habitat tolerances, and species‐specific behaviour. Mobile hydroacoustics was used to quantify habitat and depth use of bigheaded carp over four years in the heavily invaded Lower Illinois River, a major Mississippi tributary and potential dispersal pathway to the Great Lakes. Horizontally oriented transducers (combined with capture gear for species designation) enabled sampling of the main habitat features in this large flood plain river. Silver carp (Hypophthalmichthys molitrix) were dominant over bighead carp (Hypophthalmichthys nobilis) at all but one site, although habitat use was similar for both species. Densities were highest in lotic backwaters, followed by lentic backwaters and nearshore main channel, with lowest densities in the mid main channel. Bigheaded carp size and species composition were independent of habitat type. Depth associations were similar for both species, with average occurrence at 2.5–3.5 m in the main channel and 1–2 m in backwaters. However, depth relative to the river bed was largely similar across habitat types. Bigheaded carp density and depth use in the main channel were linked non‐linearly to river discharge and water temperature, respectively; densities were reduced during high discharge, whereas depth use became shallower at higher temperatures. Density–hydrology trends were less apparent in backwaters. These findings highlight critical aspects of bigheaded carp spatial ecology that will facilitate effective management in invaded and at‐risk ecosystems.  相似文献
2.
Knowledge of how invasive species use invaded habitats can aid in developing management practices to exclude them. Swan Lake, a 1100‐ha Illinois River (USA) backwater, was rehabilitated to restore ecosystem functions, but may provide valuable habitat for invasive bigheaded carps [bighead carp (Hypophthalmichthys nobilis) and silver carp (H. molitrix)]. Use (residency and passages) of Swan Lake by invasive bigheaded carps was monitored using acoustic telemetry (n = 50 individuals/species) to evaluate the use of a large, restored habitat from 2004 to 2005. Passages (entrances/exits) by bigheaded carps were highest in winter, and residency was highest in the summer. Bighead carp backwater use was associated with the differences in temperature between the main channel and backwater, and passages primarily occurred between 18:00 h and midnight. Silver carp backwater use was positively correlated with water level and main channel discharge, and fewer passages occurred between 12:00 h and 18:00 h than during any other time of day. Harvest occurring during summer or high main channel discharge could reduce backwater abundances while maintenance of low water levels could reduce overall backwater use. Conclusions from this study regarding the timing of bigheaded carps' use of backwater habitats are critical to integrated pest management plans to control invasive species. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献
3.
River modifications have altered critical habitats for fishes at a variety of spatial scales and caused global declines of many fluvial species. At small spatial scales (<1 m2), alluvial sand dunes, a ubiquitous habitat in highly modified rivers, are thought to provide energetic relief for benthic fishes in energetically costly riverine landscapes created by water flow. However, use of alluvial dune habitat is not well understood, and it is unclear whether dunes provide refuge that effectively reduces energetic costs. We designed a scale‐relevant experiment to examine the energetic responses associated with sand dune habitat in rivers. We tested whether the US federally endangered pallid sturgeon (Scaphirhynchus albus ), a benthic fish commonly associated with sand dunes, experienced reduced energetic costs with different configurations of simulated sand dune habitat. We quantified mass specific oxygen consumption (M O2; mg O2 kg−1 h−1) using intermittent flow‐through respirometry for age‐0 sturgeon (140–170 mm) in front of a sand dune, behind a sand dune and in the absence of a sand dune at two velocities (25 and 50 cm s−1) commonly observed in field studies of sturgeon habitat use. Sturgeon displayed distinct station holding behaviours for each habitat configuration. Dune location did not affect energy expenditure, but sturgeon M O2 was on average 16–20% higher in the absence of a sand dune depending on dune configuration. M O2 was on average 14% higher at 50 cm s−1 compared with 25 cm s−1. Our results provide a potential mechanism for over two decades of research on why sturgeon and other benthic fishes exhibit selection for sand dune habitat in large rivers. Fishes that select main channel habitats may depend on energetic relief provided by sand dunes, especially when other forms of structure are not available. For this reason, alluvial sand dune habitat may be important to the persistence of benthic fishes in high flow environments. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献
4.
Dams are a conservation threat because they function as barriers to native fish movement; however, they may prevent the spread of invasive species. Invasive bigheaded carps (Hypophthalmichthys spp.) threaten the Great Lakes ecosystem and are advancing towards Lake Michigan via the Illinois River. Navigation dams on the Illinois River may deter bigheaded carps' upstream movement. We investigated the permeability of the Starved Rock Lock and Dam (SRLD), the most downstream gated Illinois River dam, to bigheaded carps' migration by examining the timing of individuals approaching and passing through SRLD in relation to gate openness, tailwater elevation, and water temperature. Using acoustic telemetry of (N = ~104 per year) tagged fish, 13 upstream passages of bigheaded carps occurred through SRLD between 2013 and 2016. Eleven passages occurred through the dam gates and 2 through the lock chamber, indicating deterrents (e.g., CO2) placed in SRLD lock chamber may only limit passage of a small proportion of all fish passing through the lock‐and‐dam structure. Passages were documented only in 2013 and 2015. Most of the dam gate passages occurred during high water when gates were completely out of the water. Timing of bigheaded carps approaching SRLD was positively correlated with rising water temperature and high tailwater elevation, and all fish approached during late March through mid‐September. Movement through dams is rare; modifying gate operations to reduce gate openness during late spring and summer could further reduce the permeability of gated dams such as SRLD to bigheaded carps, slowing their upstream advance.  相似文献
5.
Modification and homogenization of habitat in large‐river ecosystems have led to the reduction of >50% of native fish species. Rehabilitating these complex ecosystems to recover fish populations requires an understanding of habitat availability and selection at multiple scales. Habitat selection by river fishes is typically assessed at the functional unit scale (100–10 000 m2). For example, in large, sand‐dominated rivers of the Central USA, alluvial islands are critical functional units for endangered sturgeon. Functional units, however, can be subdivided into mesohabitats (<100 m2), but very little is known about mesohabitat selection by large river fishes. We evaluated the mesohabitat selection of the federally endangered pallid sturgeon (Scaphirhynchus albus) and more abundant shovelnose sturgeon (Scaphirhynchus platorynchus) experimentally. We tested for selection among four common mesohabitat types that are nested within alluvial island complexes: (1) sand‐only substratum with no structure; (2) sand substratum with a sand dune structure; (3) sand substratum with simulated vegetation; and (4) a gravel‐only substratum. Sturgeon selected for the sand substratum, structureless mesohabitat, followed by the mesohabitat with a sand dune. Vegetated habitat retained less sturgeon than these two habitats but more than the gravel mesohabitat. Age‐0 pallid sturgeon and shovelnose sturgeon almost completely avoided gravel substrate, perhaps because of increased energetic costs associated with turbulent benthic flow. We posit that age‐0 sturgeon may prefer the sand and sand dune habitats over the vegetation and gravel habitats because flow may be more linear (or unidirectional) and predictable in these habitat types, whereas vegetation and gravel can create substantial benthic turbulence. Lastly, shovelnose sturgeon were on average denser in vegetated habitat than pallid sturgeon. Scaled to the population level, patterns revealed here could have implications for the macro‐distribution of both species. Restoration efforts may want to consider selection differences in the management of these two species and rehabilitation of riverine habitats. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献
6.
Identifying the appropriate scale at which habitat is biologically relevant to riverine fishes in large, sand‐dominated rivers is a challenge. Alluvial islands are important to several of these fishes throughout the central USA, but there is a paucity of information on island habitat features that restoration efforts should try to replicate. We determined the physical characteristics of two island complexes in the middle Mississippi River that facilitate the settlement and survival of age‐0 shovelnose sturgeon Scaphirhynchus platorynchus at relatively large (mean 39,000 m2) and small (mean 320 m2) scales. Depth (m), flow rate (m s−1), substrate (sand, rock, silt) and vegetation were quantified at these two scales using hydroacoustic techniques (split‐beam sonar and acoustic Doppler current profiler). Abiotic attributes in the surrounding littoral zone of the island complexes were highly correlated but differed depending on location. At the coarse spatial scale, vegetation was positively related to shovelnose sturgeon abundance. At the fine spatial scale, age‐0 shovelnose sturgeon were restricted to flow rates < 0.89 m s−1, with abundance peaking at about 0.40 m s−1. However, heterogeneity in depth and flow was important, and sturgeon abundance peaked at intermediate variability in these two abiotic attributes. A computer‐generated model of the habitat surrounding islands suggests that these habitats are diverse and may provide flow refugia and foraging patches for shovelnose sturgeon. We submit the results presented here that can contribute to a hierarchical model for island restoration in large rivers. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献
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