Habitat Rehabilitation Projects Research Articles

Abundance, cover use, and clustering of brown trout spawning redds during stream habitat rehabilitation

AbstractAbundance, placement beneath cover and clustering of brown trout spawning redds were monitored throughout five spawning seasons (2016–2020) in a 4.8‐km reach of a Minnesota coldwater stream to assess the potential impacts of concurrent stream habitat rehabilitation projects. We anticipated that redd abundance (redds/100 m stream segments) and placement beneath cover (e.g. logs and branches, boulders, overhanging bank vegetation, aquatic macrophytes) would increase and redd clustering (placement within 1.5 m of other redds) would decline as stream sections were rehabilitated. Repeated redd counts were conducted for the entire stream reach during each of the five spawning seasons, and redd cover and clustering were documented. Before‐after comparison of impact (BACI) tests were used to compare redd abundances in control versus rehabilitated stream sections, and before‐after distributional tests compared redd placement beneath cover and redd clustering within rehabilitated sections. In total, 1895 brown trout spawning redds were documented within the study reach during the five spawning seasons combined. Redd abundance increased nearly fivefold throughout the 5‐year study period (from 3.5 to 15.5 redds/100 m), but no significant difference was detected in redd abundances between rehabilitated versus control stream sections. Redd placement beneath cover (63% beneath cover in total) also increased throughout the study, but at a rate nine to 45 times greater in stream sections rehabilitated during the study than in control or previously rehabilitated sections. Redd clustering remained unchanged (5‐year means = 35 to 46% of all redds clustered) in rehabilitated sections, but increased significantly through time (0% to 35%) in the control section. Stream habitat rehabilitation did not increase spawning redd abundance or reduce redd clustering in rehabilitated stream sections, but redd placement beneath cover increased after rehabilitation to levels present in other stream sections.

Towards improving an Area of Concern: Main-channel habitat rehabilitation priorities for the Maumee River

The Maumee River watershed in the Laurentian Great Lakes Basin has been impacted by decades of pollution and habitat modification due to human settlement and development. As such, the lower 35 km of the Maumee River and several smaller adjacent watersheds comprising over 2000 km2 were designated the Maumee Area of Concern (AOC) under the revised Great Lakes Water Quality Agreement in 1987. As part of pre-rehabilitation assessments in the Maumee AOC, we assessed fish and invertebrate communities in river km 24–11 of the Maumee River to identify: 1) areas that exhibit the highest biodiversity, 2) habitat characteristics associated with high biodiversity areas, 3) areas in need of protection from further degradation, and 4) areas that could feasibly be rehabilitated to increase biodiversity. Based on benthic trawl data, shallow water habitats surrounding large island complexes had the highest fish diversity and catch per unit effort (CPUE). Electrofishing displayed similar fish diversity and CPUE patterns across habitat types early in the study but yielded no discernable fish diversity or CPUE patterns towards the end of our study. Although highly variable among study sites, macroinvertebrate density was greatest in shallow water habitats <2.5 m and around large island complexes. Our results provide valuable baseline data that could act as a foundation for developing rehabilitation strategies in the lower Maumee River and for assessing the effectiveness of future aquatic habitat rehabilitation projects. In addition to increasing in-channel habitat, watershed-scale improvements of water quality might be necessary to ensure rehabilitation strategies are successful.

Summering habitat of returning adult masu salmon &lt;i&gt;Oncorhynchus masou&lt;/i&gt; in the Jinzu River: use of pools created by a habitat rehabilitation project

富山河川国道事務所による神通川自然再生事業では，サクラマスを河川環境改善の指標種とした淵および多自然流路の整備が実施されてきた．筆者らは，今後の整備に資する知見を得ることを目的として，越夏場所として整備した淵および既存の淵におけるサクラマスの利用状況を確認するとともに，実際にサクラマスが定位していた場所の微生息環境を測定した．調査の結果，越夏場所の整備箇所ではブロック下部に静止するサクラマスが確認され，越夏場所として利用していたと考えられた．サクラマス確認地点の水深は概ね 2.0 m 以上であり，その多くにブロック等による隠れ場所が存在していた．また，サクラマスが定位していた底層の流速は平均 0.1 m/s 未満と緩やかであったのに対し，中層の流速は平均 0.3 m/s 程度と底層に比べて速かった．これらの変数を用いた統計解析の結果，サクラマスの確認地点は水深と中層の流速がともに大きいが，底層の流速は小さいということによって特徴づけられた．バイオテレメトリ調査において発信機を装着したサクラマスは，淵に滞留する個体が確認され，1 個体は整備した越夏場所に滞留していた．サクラマスに装着した水温計の水温と表層水温との間に明瞭な差は見られず，どちらもサクラマスの生息上限水温とされている 25℃ を概ね下回っていた．サクラマスが確認された場所の物理環境調査結果および統計解析結果から，これまでの越夏場所の整備にあたって必要とされてきた生息条件は妥当であり，整備した越夏場所の環境はその条件を満たしていたことが確認された．サクラマスの定位していた場所の水温は表層水温と同程度であった．水温が 25℃ を上回ることが少ない神通川においては越夏場所には必ずしも湧水の存在は必要ではなく，越夏場所の整備にあたっては上記の条件を満たすことが重要であると考えられた．

Assessing occupancy of freshwater fishes in urban boat slips of Toronto Harbour

Hardening of natural shorelines in urban aquatic ecosystems can result in a loss of fish habitat and productivity. The north shore of Toronto Harbour (Lake Ontario) has been converted to hardened boat slips for commercial, industrial and recreational purposes, but its potential utility as fish habitat has not been evaluated. The objective of this study was to determine whether fish frequented and utilized four slips in the Inner Harbour of Toronto. Two western boat slips are adjacent to some natural features and have undergone some rehabilitation to increase the complexity of aquatic habitat (i.e. addition of large substrate, overhead cover, and in-water structure). In contrast, the two eastern slips are deeper and more influenced by the turbid Don River. We assessed the timing and duration of occupancy within all four slips for seven fish species using acoustic telemetry. In just under a year, tagged fishes spent a limited amount of time in any one slip. However, there was evidence for increased use at the two western slips by Northern Pike (Esox lucius) in spring, which is likely linked to the proximity of these slips to a known spawning area. Overall, there was no reliable evidence that the majority of the seven adult fish species evaluated frequented either the western or eastern slips. Despite efforts to track and tag a variety of species, insufficient detections prevented a detailed assessment of habitat selection for the majority of species of interest. A more detailed study of the spatial ecology of these fishes is therefore needed to understand the scale of their habitat use and inform the design of habitat rehabilitation projects for hardened shorelines.

HABITATS DE DESOVA DE PEIXES MIGRADORES EM ECOSSISTEMAS LÓTICOS: CARACTERIZAÇÃO ABIÓTICA

Migratory fish species are the highly susceptible to environmental impacts as river fragmentation by dams and loss of habitats. For the implementation of reproduction habitat rehabilitation projects, information about the biotic characteristics of the spawning grounds are necessary. In this work, information of the geomorphological, hydrological and water quality characteristics of the spawning areas of migratory fishes distributed in several orders were reviewed and compared with Brazilian species. With the information found, we conclude that these studies on the spawning grounds of migratory fishes from the north hemisphere, are quite advanced, projecting a clear image of what environment in necessary for the reproduction. However in Brazil, they are still scarce, what precludes the delineation of management projects for the conservation of those species.

愛媛県重信川に造成された氾濫原生息場所における魚類群集

愛媛県重信川に造成された氾濫原生息場所における魚類群集

Fish habitat rehabilitation using wood in the world

To provide river managers and researchers with practical knowledge about fish rehabilitation, various studies of fish habitat rehabilitation that used wood were reviewed. The review focuses on fish responses, wood installation methods, and geomorphic features of the rehabilitation sites. Most studies were conducted in moderately sized (small and medium) streams with relatively high bed gradients and aimed to improve the habitats of salmonid species. In this stream type, structures spanning the full (log dam) and partial (log deflector) width of the river were most common, and wood structures that created pools and covers were successful in improving fish habitat. Some projects were conducted in moderately sized low-gradient streams, in which wooden devices used to create instream cover were effective for fish assemblages. There were few studies in other aquatic ecosystems. However, well-designed large wood structures, known as engineered log jams, were used in rehabilitation projects for large rivers. In slack-water or lentic systems such as side-channels, estuaries, and reservoirs, small and large wood structures that created cover were used to improve habitat for many fish species. For successful fish habitat rehabilitation projects, the hydrogeomorphic conditions of rehabilitation sites should be carefully examined to avoid physical failure of wood structures. Although artificial wood structures can be used to improve fish habitat in various aquatic ecosystems, they should be considered to be a complementary or interim habitat enhancement technique. The recovery of natural dynamic processes at the watershed scale is the ultimate target of restoration programs.

Greater Sage‐Grouse Centrocercus urophasianus Use of Threetip Sagebrush Relative to Big Sagebrush in South‐Central Idaho

Disturbances that change sagebrush Artemisia spp.‐steppe communities may have an impact on greater sage‐grouse Centrocercus urophasianus populations. Fire can rapidly alter sagebrush‐steppe communities and may result in an increase in threetip sagebrush A. tripartita because this shrub is one of the few species of sagebrush that will sprout following fire. We examined the use of threetip sagebrush by sage‐grouse as nest cover and compared nest success of grouse using threetip sagebrush to that of grouse using big sagebrush A. tridentata. Sage‐grouse used threetip sagebrush as nest cover less than expected based on the abundance of this shrub. The only other species of sagebrush used as nest cover was big sagebrush, and sage‐grouse used big sagebrush more than expected based on big sagebrush abundance. However, nest site selection was confounded by age of sage‐grouse females. Sage‐grouse that used big sagebrush as nest cover had greater nest success than grouse using threetip sagebrush. Our findings demonstrate another negative, but subtle, effect of fire on sage‐grouse populations and further underscore the need for fire suppression and carefully implemented habitat rehabilitation projects.

Stream bed organic carbon and biotic integrity

Allochthonous carbon is the basis of the detrital food web in low-order, warmwater stream ecosystems, and stream-bed sediments typically function as carbon reservoirs. Many of the same factors that govern carbon input and storage to streams (e.g. riparian vegetation, large wood, heterogeneous boundaries) have also been identified as key attributes of stream fish habitat. 2. Effects of channel incision on sand-bed stream carbon reservoirs and indices of biological integrity (IBIs) based on fish collections were examined for four streams exhibiting a range of incisement in northern Mississippi. Observed mean C concentrations (mass percentage) ranged from 0:24 � 0:36% for a non-incised stream to only 0:01 � 0:02% for a severely incised channel, and were not correlated with large wood (LW) density, perhaps because LW density at one site was elevated by a habitat rehabilitation project and at another site by accelerated inputs from incision-related riparian tree fall. Fish IBI was positively correlated with bed C (r ¼ 0:70; p ¼ 0:003), and IBIs for reference streams were more than 50% greater than those computed for the most severely degraded sites. 3. More testing is needed to determine the efficacy of stream bed C as an indicator, but its importance to warmwater stream ecosystems, and the importance of covarying physical and hydrologic conditions seems evident. Published in 2008 by John Wiley & Sons, Ltd.

Construction constraints for geomorphic‐unit rehabilitation on regulated gravel‐bed rivers

AbstractThe emergent practice of applied river restoration uses best available equipment and contouring methods to construct detailed designs with some features at scales as small as 0.5‐m relief. As part of adaptive management, it is necessary to determine the practicability of design features and construction methods before widespread adoption. In this study, we compared design versus as‐built topography for five salmonid spawning habitat rehabilitation projects at riffle‐pool geomorphic units on the lower Mokelumne River, California, USA. These were built instream using rubber tire front loaders. Digital elevation models (DEMs) of each site were produced for pre‐project, design and as‐built conditions. DEM differencing was used to compare the as‐built surface against corresponding design surfaces at each site to identify deviations. Causes of each identified deviation were assessed based on subjective observations by a team during construction. Across the projects, 70% of as‐built topography was within ±0.15 m of design specifications. Of the 30% deviating from the design, 41% was overfilled and 59% underfilled. The 30% of rehabilitated channel area that deviated from designs did not affect predicted areas of high‐quality spawning habitat. On‐site factors that hindered accurate construction of designs included front loader fording depth, poor operator elevation estimation, operator spatial disorientation and wood obstructions. In addition, funding and project management uncertainties caused gravel supply deficits and gravel bulk density estimation errors. It is concluded that constructing broad (&gt;0.5‐m relief) features of process‐based salmonid spawning habitat rehabilitation projects by gravel augmentation is practicable. However, uncertainties attributed to human error and available methods inhibit detailed (&lt;0.5‐m relief) rehabilitation. Despite uncertainties, limitations and errors, following the recommendations reported in this study would improve the as‐built adherence to design specifications of future projects. Copyright © 2008 John Wiley &amp; Sons, Ltd.

Three-dimensional numerical simulation of flow around stream deflectors: The effect of obstruction angle and length

Fish habitat rehabilitation projects often use paired stream deflectors to increase bed shear stress and maintain a deep pool. Many of these projectshave been unsuccessful, mainly because of the lack of knowledge of the complex three-dimensional (3D) flow dynamics created by the deflectors.A 3D numerical model was used to simulate the flow field around stream deflectors in a laboratory flume. Predicted velocities were successfullyevaluated against laboratory measurements. Deflectors ranging from contraction ratios of 0.1 -0.35 oriented to flow at angles of 30-150° were used forthe simulations. Results show that the upstream dynamic pressure maximum, upstream flow separation distance, upstream downwelling extent, andtotal downwelling distance all increase with deflector angles. However, local minimum dynamic pressure, nose velocity amplification, downstreamdownwelling extent, and flow contraction width are maximized at angles closer to 90°. In general, maximum downwelling magnitudes increase forlonger deflectors, with the greatest values being found for the 135° deflectors. Increasing the length of the deflectors tends to amplify most of the flowparameters. These findings have important implications for the design of paired deflectors in fish habitat rehabilitation projects where the objective isto maximize the pool size downstream of the obstructions.

Forest stand restoration in the agricultural landscape: The effect of different methods of planting establishment

On the arable land of the Valová River floodplain, Czech Republic, experimental plantings of native woody plants were established within a habitat rehabilitation project. This study evaluates the growth of planted seedlings in response to four commonly used methods of planting establishment: (a) grassing the whole area (without mulch), (b) mulching with fresh bark in rows, (c) mulching the whole area with straw, and (d) mulching with textile fleece in rows. The following woody plants were used: (a) trees: Quercus robur L., Carpinus betulus L., Fraxinus excelsior L., Acer campestre L., A. platanoides L., Tilia cordata Mill., Prunus padus L., P. avium L.; (b) shrubs: Euonymus europaea L., Crataegus monogyna Jacq., Viburnum opulus L., Corylus avellana L., Ligustrum vulgare L., and Cornus sanguinea L. Growth rate of the seedlings planted was monitored throughout a 5-year period. The tree and shrub seedlings mulched on the whole area with straw showed a two- or three-times higher growth, i.e., the fastest in comparison with grassing and mulching using bark and textile fleece in rows. The positive impact of straw mulch was highly significant for bare-root tree seedlings and less significant for shrub seedlings with roots in soil. Results of the work show that the method of planting establishment can significantly influence seedling development and prosperity, and that at the same financial costs, significantly different results can be obtained. Throughout the 5-year period, however, no significant difference in the overall growth rate trends, i.e., the shape of the growth curves, for all woody species planted, except Prunus avium, Tilia cordata and Crataegus monogyna, established using different methods was found.

Challenging the assumption of habitat limitation: an example from centrarchid fishes over an intermediate spatial scale

AbstractHabitat rehabilitation efforts are predicated on the frequently untested assumption that habitat is limiting to populations. These efforts are typically costly and will be ineffective if habitat is not limiting. Therefore it is important to assess, rather than assume, habitat limitation wherever habitat rehabilitation projects are considered. Catch‐count data from a standardized probability‐based stratified‐random monitoring programme were examined for indirect evidence of backwater habitat limitation by centrarchid fishes in the Upper Mississippi River System. The monitoring design enabled fitting statistical models of the association between mean catch at the spatial scale of tens of river kilometres and the percentage of contiguous aquatic area in backwater at least 1 m deep by maximizing a stratum‐area weighted negative binomial log‐likelihood function. Statistical models containing effects for backwater limitation failed to account for substantial variation in the data. However, 95% confidence intervals on the backwater parameter estimates excluded zero, indicating that population abundance may be limited by backwater prevalence where backwaters are extremely scarce. The combined results indicate, at most, a weak signal of backwater limitation where backwaters are extremely scarce in the lower reaches, but not elsewhere in the Upper Mississippi River System. This suggests that habitat restoration projects designed to increase the area of backwaters suitable for winter survival of centrarchids are unlikely to produce measurable benefits over intermediate spatial scales in much of the Upper Mississippi River System, and indicates the importance of correct identification of limiting processes. Published in 2004 by John Wiley &amp; Sons, Ltd.