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1.
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   

2.
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   

3.
A baseline assessment of the Missouri River fish community and species‐specific habitat use patterns conducted from 1996 to 1998 provided the first comprehensive analysis of Missouri River benthic fish population trends and habitat use in the Missouri and Lower Yellowstone rivers, exclusive of reservoirs, and provided the foundation for the present Pallid Sturgeon Population Assessment Program (PSPAP). Data used in such studies are frequently zero inflated. To address this issue, the zero‐inflated Poisson (ZIP) model was applied. This follow‐up study is based on PSPAP data collected up to 15 years later along with new understanding of how habitat characteristics among and within bends affect habitat use of fish species targeted by PSPAP, including pallid sturgeon. This work demonstrated that a large‐scale, large‐river, PSPAP‐type monitoring program can be an effective tool for assessing population trends and habitat usage of large‐river fish species. Using multiple gears, PSPAP was effective in monitoring shovelnose and pallid sturgeons, sicklefin, shoal and sturgeon chubs, sand shiner, blue sucker and sauger. For all species, the relationship between environmental variables and relative abundance differed, somewhat, among river segments suggesting the importance of the overall conditions of Upper and Middle Missouri River and Lower Missouri and Kansas rivers on the habitat usage patterns exhibited. Shoal and sicklefin chubs exhibited many similar habitat usage patterns; blue sucker and shovelnose sturgeon also shared similar responses. For pallid sturgeon, the primary focus of PSPAP, relative abundance tended to increase in Upper and Middle Missouri River paralleling stocking efforts, whereas no evidence of an increasing relative abundance was found in the Lower Missouri River despite stocking. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

4.
It is hypothesized that slow, shallow water habitats benefit larval pallid sturgeon Scaphirhynchus albus; however, testing this hypothesis is difficult, given the low number of larval pallid sturgeon present in large rivers. In contrast, relatively large numbers of age‐0 shovelnose sturgeon Scaphirhynchus platorynchus have been sampled, providing a potentially useful baseline to assess the importance of slow, shallow water to age‐0 sturgeon of both species (hereafter age‐0 sturgeon) in the lower Missouri River. Thus, we investigated the potential relationships between the prevalence of shallow water <1.5 m and the age‐0 sturgeon catch rates at multiple scales. Age‐0 sturgeon were usually sampled in water >1.5 m, and catch rates were usually highest in the upper half [i.e. river kilometre (RKM) 400 to 800] of the lower Missouri River study area, whereas the availability of water <1.5 m was usually highest in the lower half (i.e. RKM 0 to 400). Similarly, there was no relationship between age‐0 sturgeon mean catch‐per‐unit effort and ha/km of water <1.5 m at any studied scale. Our results may suggest that shallow water, as currently defined, may not be a suitable surrogate for assessing efforts to address pallid sturgeon population declines. However, it is still unknown if lack of appropriate habitat is currently limiting pallid sturgeon. Published 2015. This article is a U.S. Government work and is in the public domain in the USA. River Research and Applications published by John Wiley & Sons Ltd.  相似文献   

5.
A river's flow regime creates and maintains spatial variability in habitat and dictates the distribution and abundance of riverine fishes. Changes to patterns of natural hydrologic variation and disturbance create novel flow conditions and may influence distribution of native fishes. We examined local and regional‐scale factors that influenced the presence of pallid sturgeon Scaphirhynchus albus in the Platte River, a large tributary to the Missouri River in Nebraska, USA. Daily river discharge, diel flow variability, season and location in the study area were the most supported variables in logistic regression models explaining pallid sturgeon distribution. The probability of pallid sturgeon occurrence was greatest during periods of high discharge (>90th percentile flows) in the spring and fall. Pallid sturgeon occurrence was always lower when variability in diel flow patterns was high (i.e. hydropeaking). Our results indicate that pallid sturgeon use of the lower Platte River was strongly tied to the flow regime. Therefore, the lower Platte River may provide an opportunity to preserve and restore sturgeon and possibly other large‐river fishes through appropriate water management strategies. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

6.
After the pallid sturgeon (Scaphirhynchus albus) was listed as endangered in 1990, a variety of management actions focusing on early life history needs have been implemented to aid species recovery. Given the scarcity of age‐0 pallid sturgeon, managers and scientists have relied on sympatric congeners to evaluate the effectiveness of management actions in the short term; however, increased understanding of habitat requirements for age‐0 Scaphirhynchus sturgeon is still needed to appropriately focus management efforts. Recently, a lack of food‐producing and foraging habitats were proposed as potential limiting factors for pallid sturgeon, and the purpose of this study was to evaluate the current definition of these habitats at multiple spatial scales using data from age‐0 Scaphirhynchus sturgeon (shovelnose sturgeon [Scaphirhynchus platyrhynchus] or hybrid [shovelnose sturgeon x pallid sturgeon]). Results showed the water depths and velocities that currently define age‐0 pallid sturgeon foraging habitat had little effect on age‐0 Scaphirhynchus sturgeon prey consumption. Similar results occurred when evaluating the relationship between prey consumption and food‐producing habitat present 10, 20, and 30 days before capture. Assuming that individuals captured during this study were a valid surrogate, these results suggest that increasing foraging and food‐producing habitat as defined by the current depth and velocity criteria is unlikely to result in the desired benefits of increased growth and survival of age‐0 pallid sturgeon.  相似文献   

7.
The spatial variability in demographic parameters represents fundamental information for conservation and management of large‐river fish populations. We assessed demographic processes including survival and movement across macroscale habitats in a large‐river network using 2 candidate large‐river species with contrasting life history strategies. We used mark–recapture data and a multistate model framework to estimate survival and transition probabilities between main‐stem and tributary habitats for both channel catfish and shovelnose sturgeon. Annual survival for channel catfish was similar in main‐stem and tributary habitats (range in S = 0.47–0.58). Annual survival for shovelnose sturgeon was less in the tributary (S = 0.68) compared with the main stem (S = 0.83). The probability of movement among macroscale habitats differed between species. However, the greatest probability of movement occurred from the tributary to the main‐stem for both channel catfish (ψ = 0.42) and shovelnose sturgeon (ψ = 0.27). Movement between main‐stem and tributary rivers may be a prominent characteristic for both channel catfish and shovelnose sturgeon and could influence population demographic rates and abundance across systems. Riverine fish populations are likely structured across multiple salient scales—including tributary and main‐stem habitats. Consideration of connectivity across tributary and main‐stem habitats with respect to species' life history strategy and life stage may better integrate a systems' perspective for conservation and management of large‐river fish populations.  相似文献   

8.
Flow regulation and water abstractions may change the complex relationship between river hydraulics, morphology, and riparian vegetation. As a result, rivers are likely to decrease their dynamics, increase the amount of vegetation, and modify their habitat structure. Flood events provide a natural mechanism for removal of invasive vegetation and recreation of natural floodplain habitats. This work aims at evaluating and quantifying how gravel‐bed braided rivers naturally control vegetation encroachment through morphological processes and the impact of both naturally occurring and induced avulsions. Flume experiments were conducted in a 24‐m‐long x 1.6‐m‐wide channel filled with well‐sorted sand and constant longitudinal gradient at 0.01 m/m. Once a braided network developed, the flume was seeded with Eruca sativa at a density of 1.5 seeds/cm2 and grown until an approximate height of 1.1 cm. Experiments evaluated low‐, medium‐, and large‐flood events and documented morphological changes and impacts to vegetation at four intervals during the experiments. High‐resolution images captured approximately 3 m above the flume were used to produce accurate Structure‐from‐Motion‐derived topography and orthoimagery (average errors 2 mm). Vegetation dynamics were observed to be highly variable and depend on local morphological changes and bank erosion. Discharge is the first‐order control on vegetation removal, but our results show that occurrence of avulsions significantly increases vegetation removal. The experiments highlight that a relatively small amount of sediment relocation can be an effective tool to induce avulsions and reduce vegetation encroachment on regulated rivers.  相似文献   

9.
Rivers worldwide have experienced changes through habitat modifications and are likely further exacerbated with the onset of climate change. The coupling of these anthropogenic disturbances has reduced the ability of river ecosystems and associated biota to adjust. The aforementioned human‐induced habitat perturbations coupled with high summer river temperatures have been associated with an increased frequency of fish kills. Recently, shovelnose sturgeon Scaphirhynchus platorynchus have experienced numerous events of excessive summer mortality in rivers across the USA. During the summer of 2012, multiple fish kills occurred on the lower Des Moines River. During one of these events, we collected numerous dead or dying shovelnose sturgeon (N = 132) to explore factors causing mortality. Water temperatures were exceedingly high (29–35°C), while dissolved oxygen levels varied between 4 and 10 mg L?1. Based on population simulation modelling, only ~14% mortality would need to occur to reduce the reproductive potential below sustainable levels, which was likely exceeded. The results of our controlled experiment demonstrate that the high temperature in the Des Moines River was likely the mechanism initiating mortality. Future climate projections indicate that increases in temperature on the Des Moines River are possible; thus, the population may be at risk in the future. Through our microchemistry investigation, immigration from the Upper Mississippi River appears to be common and may be a source population to the Des Moines River. Despite immigration, the influence that these mortality events have on the Upper Mississippi River is unknown. Thus, proactive management efforts are needed to ensure sustainability of this population. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

10.
We conducted a regional classification and analysis of riverine floodplain physical features that represent key attributes of salmon rearing habitats. Riverine habitat classifications, including floodplain area and river channel complexity, were derived at moderate (30 m) spatial resolution using multispectral Landsat imagery and global terrain data (90 m) encompassing over 3 400 000 km2 and most North Pacific Rim (NPR) salmon rivers. Similar classifications were derived using finer scale (i.e. ≤ 2.4‐m resolution) remote sensing data over a smaller set of 31 regionally representative flood plains. A suite of physical habitat metrics (e.g. channel sinuosity, nodes, floodplain width) were derived from each dataset and used to assess the congruence between similar habitat features at the different spatial scales and to evaluate the utility of moderate scale geospatial data for determining abundance of selected juvenile salmon habitats relative to fine scale remote sensing measurements. The resulting habitat metrics corresponded favorably (p < 0.0001) between the moderate scale and the fine scale floodplain classifications; a subset of these metrics (channel nodes and maximum floodplain width) also were strong indicators (R2 > 0.5, p < 0.0001) of floodplain habitats defined from the finer scale analysis. These relationships were used to estimate the abundance and distribution of three critical shallow water floodplain habitats for juvenile salmon (parafluvial and orthofluvial springs, and shallow shore) across the entire NPR domain. The resulting database provides a potential tool to evaluate and prioritize salmon conservation efforts both within individual river systems and across major catchments on the basis of physical habitat distribution and abundance. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

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