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- 1 The combination of elements from geomorphology, open-channel hydraulics, and hydraulic habitat requirements of stream fish forms the basis for an ecologically sound ‘soft engineering’ of river channels.
- 2 Interpreting and mapping the hydraulic geometry of streams and locally varied flow conditions can be accomplished with plane table surveys and customized field-data sheets. This information can serve to manage hydraulic habitats preferred by fish.
- 3 The use of fluvial characteristics to design preferred hydraulic habitats is illustrated in two examples: (i) a walleye (Stizostedion vitreum vitreum Mitchill) spawning rehabilitation project undertaken in a stream channelized as a lowland drainage canal, and (ii) a trout (Salvelinus fontinalis Mitchill and Oncorhynchus mykiss Walbaum) habitat-enhancement project to create additional holding and resting areas for adult fish in a stream paved with glacially deposited boulders modified by a road crossing.
- 4 In both examples the ‘soft engineering’ of the river channels enhanced the hydraulic fish habitat.
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William W. Duncan Robin B. Goodloe Judy L. Meyer Eric S. Prowell 《Restoration Ecology》2011,19(1):64-73
Incised river channels are dynamic components of fluvial systems, represent geomorphic degradation, and are encountered worldwide. Ecological effects of incision can be far‐reaching, affecting habitat availability and channel processes. Although incision can reflect habitat degradation, some studies suggest that important in‐stream habitats do not differ with the degree of incision. Therefore, we tested whether in‐stream habitat variables that are important to imperiled fishes differ in river reaches with varying degrees of incision. Because incision (measured using entrenchment ratio) had no discernable effect on in‐stream habitat characteristics (i.e., proportion fines, gravel, cobble, and macrophyte occurrence and length), we expanded our analysis to assess the effects of 29 additional geomorphic variables on in‐stream habitat. These analyses indicated that bank height, bed mobility, D84, cross‐sectional area, bankfull width, and wetted perimeter accounted for 42% of macrophyte occurrence and 64% of macrophyte length variance. Postflood surveys indicated that macrophyte occurrence on cobble declined as bank height and bed mobility increased, and sediment size decreased, suggesting that sediment size and bed mobility have a stronger influence on in‐stream habitat than incision. Although channel incision often indicates environmental degradation, important aspects of habitat are not described by this measurement. Strategies that depend on incision to identify restoration sites may have limited habitat benefits in Southeastern Piedmont streams and rivers. Instead, landscape or shoal‐scale restoration approaches that increase coarse sediment proportions may increase macrophyte occurrence, length, and persistence. Sediment budgets that identify coarse and fine sediment sources and transport may be useful to prioritize restoration approaches. 相似文献
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Creating a habitat for a variety of forms of life, such as riparian plants and various fish, is a necessity for stressed river ecosystems. In this study, the hydraulic characteristics of a fish habitat in an urban channel were analyzed using River2D, which is a two-dimensional (2D) depth-averaged finite element hydrodynamic model, to improve the habitat of two target fish in the Daejeon Stream, Korea. These species are Pseudopungtungia nigra, which is an endangered species in the Daejeon Stream, and Zacco platypus, which is a dominant species. In addition, changes in the weighted usable area (WUA) were compared and reviewed as boulders were placed in the stream. The best method for improving the P. nigra's habitat is proposed. A simulation analysis was performed on urban rivers for fish habitats. As a result, a straight and monotonous urban river flow was found to be an appropriate habitat environment for Z. platypus. The WUA for Z. platypus was about 20 times greater than that for P. nigra. Three different fish habitat enhancement methods were evaluated by calculating the WUA for the target fish in the study channel. By calculating the WUA to create fish habitats, the V-type riffle method was found to increase the usable area of the habitat environment for P. nigra by 360%, and the step stone method and single boulder method did so by 60% and 8%, respectively. For the single boulder method, boulders were placed in the channel bed at 3.5-m intervals, which significantly increased habitat availability. Moreover, centralizing the flow pattern in the channel among several types of boulder placements greatly expanded the habitat for P. nigra. Thus, an appropriate placement interval and boulder location that considers the characteristics of the riverbed and target fish species should be researched and implemented. 相似文献
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Many successful invasions have taken place in systems where harmful disturbance has changed habitat conditions. However, less attention has been paid to the role of habitat restoration, which modifies habitats and thus also has the potential to facilitate invasions. We examined whether in‐stream habitat restorations have the potential to either facilitate or resist invasion by two widely introduced non‐native stream salmonids, Salvelinus fontinalis Mitchill and Oncorhynchus mykiss Walbaum, in Finland. A physical habitat simulation system was used to calculate whether the habitat area for the target species increased or decreased following the restorations. For comparison, we also reported results for four native stream fish species. The simulations showed that the restored streams provided the highest amount of usable habitat area for the native species, particularly for Salmo salar L. and Gottus gobio L. However, it was interesting to note that the restorations significantly increased habitat quality for the two non‐native species, especially at low flows. Nevertheless, the non‐native species had the lowest amount of usable habitat area overall. The modeling results indicated that not only habitat destruction but also habitat restoration could contribute to the spread of non‐native species. Fisheries and wildlife managers should be aware of the possibility, when restoring habitats in order to preserve native ecosystems, that non‐native species could manage to gain a foothold in restored habitats and use them as population sources for further spread. Knowing the widespread negative effect of non‐native species, this risk should not be underestimated. 相似文献
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Rachel L. Malison Mark S. Lorang Diane C. Whited Jack A. Stanford 《Freshwater Biology》2014,59(6):1229-1246
Our aim was to determine how beavers affect habitats and food resources for juvenile salmon in the Kwethluk River in western Alaska.
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Abstract Habitat availability is often regarded as the primary factor that limits population and community recovery in degraded ecosystems, and physical habitat is thus often targeted in restoration. The identification of which habitat(s) to attempt to restore is a critical step in the restoration process, but one for which there is often a paucity of useful information. Here we examine the distribution of fish in three lowland streams in Victoria, Australia, that have been degraded by severe sedimentation. We aim to identify habitats that are associated with high abundances of native fish, and that thus might be appropriate to target in habitat restoration. Associations between native fish abundances and physical habitat characteristics were examined at three spatial scales (among streams, among sites and within sites) to determine the types of habitat to which fish respond, and the scales over which these responses occur. Of the four species of native fish found in the streams, three (Galaxias olidus Günther, Gadopsis marmoratus (Richardson) and Nanoperca australis Günther) showed significant habitat associations at small spatial scales (i.e. within sites). In particular, these species were generally found in deeper water, and in close proximity to cover (typically either coarse or fine woody debris or vegetation). Differences in habitat availability among sites and streams were less influential, except in the case of G. marmoratus, which was completely absent from both the ephemeral streams. Although our results suggest that these species collectively respond to habitat at several spatial scales, fish distributions were allied to the presence of habitat structure at the scale of metres, the smallest spatial scale examined. We hypothesize that fish abundances are currently limited by the low availability of habitat at these small spatial scales. It may therefore be possible to increase fish abundances in these creeks by augmenting the amount of available habitat via stream restoration. 相似文献