Streamflow alteration and habitat ramifications for a threatened fish species in the Central United States

In the Central United States, the Arkansas darter (Etheostoma cragini) is listed as a threatened fish species by the State of Kansas. Survival of the darter is threatened by loss of habitat caused by changing streamflow conditions, in particular flow depletion. Future management of darter populations and habitats requires an understanding of streamflow conditions and how those conditions may have changed over time in response to natural and anthropogenic factors. In Kansas, streamflow alteration was assessed at 9 U.S. Geological Survey streamgages in 6 priority basins with no pronounced long‐term trends in precipitation. The assessment was based on a comparison of observed (O) and predicted expected (E) reference conditions for 29 flow metrics. The O/E results indicated a likely or possible diminished flow condition in 2 basins; the primary cause of which is groundwater‐level declines resulting from groundwater pumping for irrigated agriculture. In these 2 basins, habitat characteristics adversely affected by flow depletion may include stream connectivity, pools, and water temperature. The other 4 basins were minimally affected, or unaffected, by flow depletion and therefore may provide the best opportunity for preservation of darter habitat. Through the O/E analysis, anthropogenic streamflow alteration was quantified and the results will enable better‐informed decisions pertaining to the future management of darters in Kansas.     

Effect of aquatic mosses on juvenile fish density and habitat use in the regulated River Suldalslågen,western Norway

Two morphologically distinct moss communities were found in the River Suldalslågen. The liver moss community consists of species which form a dense mat on the bottom, while the river moss (Fontinalis) community forms long tufts. Moss growth has increased since hydropower regulations due to reduced floods and increased winter flows. Increased moss cover affects the bottom structure, as well as intra‐gravel and near‐bottom hydraulics. We studied densities of juvenile Atlantic salmon (Salmo salar) and brown trout (Salmo trutta) by electrofishing and habitat selection by direct underwater observation, in areas with natural moss cover compared with areas where mosses were experimentally removed. Areas with dense mats of liver mosses held lower densities of young of year (YoY) and older salmon parr than areas where liver moss had been removed. No differences in densities of YoY salmon were found between areas with and without Fontinalis. For older salmon, parr results were inconclusive. In some samples more and in others fewer fish were found in areas with Fontinalis moss removed. For trout, densities were higher in areas with Fontinalis, while results for liver moss were inconclusive. No major differences were found with regard to microhabitat selection between areas with and without river moss, suggesting that habitat quality in these areas was similar during summer, except with respect to substrate. Salmon held more exposed positions in areas without liver moss, but this is mainly attributed to different habitat availabilities. It is concluded that the relative increase in liver mosses in the River Suldalslågen has a negative impact on juvenile Atlantic salmon fish density. Copyright © 2002 John Wiley & Sons, Ltd.     

Diel patterns in spatial distribution of fish assemblages in lentic and lotic habitat in a regulated river

Fish assemblages in large rivers are governed by spatio‐temporal changes in habitat conditions, which must be accounted for when designing effective monitoring programmes. Using boat electrofishing surveys, this study contrasts species richness, catch per unit effort (CPUE), total biomass, and spatial distribution of fish species in the Saint John River, New Brunswick, Canada, sampled during different diel periods (day and night) and macrohabitats (hydropower regulated river and its reservoir) in the vicinity of the Mactaquac (hydropower) Generating Station. Taxa richness, total CPUE, and total biomass were significantly higher during night surveys, resulting in marked differences in community composition between the two diel periods. Furthermore, the magnitude of diel differences in catch rate was more pronounced in lentic than in lotic macrohabitats. The required sampling effort (i.e., number of sites) to increase accuracy and precision of CPUE estimates varied widely between fish species, diel periods, and macrohabitats and ranged from 15 to 185 electrofishing sites. Determining a correction factor to contrast accuracy and precision of day‐ with night‐time surveys provide useful insights to improve the design of long‐term monitoring programmes for fish communities in large rivers. The study also shows the importance of multihabitat surveys to detect differences in the magnitude of diel changes in fish community metrics.     

Downstream environmental effects of dam operations: Changes in habitat quality for native fish species

Hydropeaking dam operation and water extractions for irrigation have been broadly stated as alterations to natural flow regimes, which have also been noticed in the Biobío Watershed, in Central Chile, since 1996. In the Biobío River, most of native fish species are endemic and very little is known about them. Their ecological and social values have never been estimated, and there is lack of information about their habitat preferences. Furthermore, changes on fish habitat availability due to natural and/or man‐made causes have not been evaluated. In this study, eight native fish species, in a representative reach of the Biobío River, were studied and their preferred habitats were surveyed and characterized. A hydrodynamic model was built and linked to the fish habitat simulation model CASiMiR. Fuzzy rules and fuzzy sets were developed for describing habitat preference of the native fish species. CASiMiR was then used to simulate how physical habitat conditions vary due to flow control (i.e. upstream dams). Results show how overall habitat quality, expressed as weighted usable area (WUA) and hydraulic habitat suitability (HHS), changes and fluctuates due to the dam operation and how the daily hydropeaking is influencing quantity, quality and location of different habitats. The study suggests that the analysed fish are highly susceptible to flow control, as dams are currently operated, and fish habitat improvement suggestions are proposed. Copyright © 2010 John Wiley & Sons, Ltd.     

松花江流域主要干支流纵向连通性与鱼类生境

基于松花江流域拦河建筑物现状,采用阻隔系数法,评价主要干支流的纵向连通性。结果表明:松花江干流和嫩江纵向连通性指数分别为0.21和0.27,连通性评价等级为良,第二松花江连通性指数为0.62,连通性评价等级为中等。嫩江支流中连通性最好的是嫩江,成为冷水性鱼与嫩江尼尔基以下河段交流的唯一通道;而甘河、雅鲁河、绰尔河和讷谟儿河连通性评价等级为良,洮儿河、霍林河和乌裕尔河连通性评价等级为劣。第二松花江支流中伊通河和饮马河拦河坝众多,鱼类洄游受阻,连通性等级为劣。松花江干流支流牡丹江、拉林河受梯级水电站开发影响,其评价指数为劣;倭肯河、汤旺河受河流沿岸灌区渠首闸坝、水库及水电站建设影响,评价等级为差,这些支流目前濒危珍稀鱼类已绝迹,也极少见到冷水性鱼类。整个流域内未建设过鱼设施,对鱼类洄游和种群交流产生阻隔,提出了补建和新建过鱼设施,必要时开展增殖放流的措施。建议对没有预留生态流量的拦河建筑物进行改造或者利用现有设施泄放生态流量,对预留生态流量的调整水库调度方案保证其下泄流量满足不同时间、空间鱼类生存需求。     

水电站减水河段鱼类生境需求的水力参数

本文对雅砻江锦屏二级减水河段，依据国外提出的Tennent法、R2Cross法中对水力生境参数描述，以及相关冷水鱼大西洋鲑和褐鳟产卵期对水力生境参数的报导，结合该河段鱼类生境的具体情况，对目标鱼类的水力生境需求问题进行了探讨。确定了河段鱼类生境需求的流速、水深、水面宽、湿周、水温等水力参数。为确定鱼类生境需求的水力参数进行了探索性的工作。     

Dam effects on bedload transport on the upper Santa Ana River,California, and implications for native fish habitat

Dams disrupt the flow of water and sediment and thus have the potential to affect the downstream geomorphic characteristics of a river. Though there are some well‐known and common geomorphic responses to dams, such as bed armouring, the response downstream from any particular dam is dependent on local conditions. Herein, we investigate the response of the upper Santa Ana River in southern California, USA, to the construction of a large dam at the transition from mountains to valley, using calculations of bedload transport capacity on the mainstem below the dam and for major tributaries. Approximate sediment budgets were constructed for downstream reaches to estimate deposition and erosion rates for sand, gravel, and cobble particle sizes. Our results indicate that the classical response of bed armouring and erosion is likely limited to a short reach immediately below the dam. Farther downstream, though transport capacity is reduced by flow regulation by the dam, the channel reaches are likely to remain depositional but with reduced deposition rates. Persistent deposition, as opposed to erosion, is the result of the replenishment of flow and sediment supply by large downstream tributaries. In addition, the calculations indicate that the composition of the bed is unlikely to change substantially in downstream reaches. A Monte Carlo approach was employed to estimate the uncertainty in the sediment budget predictions. The impacts of the dam on the geomorphic character of the river downstream could have implications for native fish that rely on coarse substrate that supports their food base.     

Spatial distribution and geomorphic condition of fish habitat in streams: an analysis using hydraulic modelling and geostatistics

Reach‐scale physical habitat assessment scores are increasingly used to make decisions about management. We characterized the spatial distribution of hydraulic habitat characteristics at the reach and sub‐reach scales for four fish species using detailed two‐dimensional hydraulic models and spatial analysis techniques (semi‐variogram analyses). We next explored whether these hydraulic characteristics were correlated with commonly used reach‐scale geomorphic assessment (RGA) scores, rapid habitat assessment (RHA) scores, or indices of fish biodiversity and abundance. River2D was used to calculate weighted usable areas (WUAs) at median flows, Q₅₀, for six Vermont streams using modelled velocity, depth estimates, channel bed data and habitat suitability curves for blacknose dace (Rhinichthys atratulus), brown trout (Salmo trutta), common shiner (Notropis cornutus) and white sucker (Catostomus commersoni) at both the adult and spawn stages. All stream reaches exhibited different spatial distributions of WUA ranging from uniform distribution of patches of high WUA to irregular distribution of more isolated patches. Streams with discontinuous, distinct patches of high score WUA had lower fish biotic integrity measured with the State of Vermont's Mixed Water Index of Biotic Integrity (MWIBI) than streams with a more uniform distribution of high WUA. In fact, the distribution of usable habitats may be a determining factor for fish communities. A relationship between predicted WUAs averaged at the reach scale and RGA or RHA scores was not found. Future research is needed to identify the appropriate spatial scales to capture the connections between usable patches of stream channel habitat. Copyright © 2008 John Wiley & Sons, Ltd.     

Patterns of species richness and introduced species in native freshwater fish faunas of a Mediterranean‐type basin: the Guadiana River (southwest Iberian Peninsula)

In this study, we analysed the factors affecting species richness and introduced species component patterns in native fish faunas of 30 streams of the Middle Basin of the Guadiana River. From a principal component analysis and a stepwise multiple regression analysis performed on a data matrix composed of ten hydrological and biotic variables, we showed that: (1) fish species richness increased with stream length and watershed area, (2) the number of native species in a stream declined as channelizations and river regulation (constructions of dams) are higher, whereas introduced species increased in the same way, (3) the two main negative factors affecting native ichthyofaunas affected dissimilar ecological areas: channelizations, which depend on land‐use intensity of floodplain, mainly occurred in lower reaches of streams, but construction of dams mainly took place in upper sections of rivers, (4) the length of the remaining well‐preserved reaches in a stream appeared to be the only factor accurately predicting native fish species richness, and (5) native fish faunas of small isolated streams are more vulnerable to habitat alteration than those of large streams. Both isolation and fragmentation of populations were recorded, so the conservation status of native and highly endemic fish fauna of the study area is extreme. Protection of the few still extant, well‐preserved small streams and upper reaches, habitat restoration of channeled areas, and inclusion of the need for native fish fauna conservation in long‐term public planning of water use become a priority. Fish communities appear to be a sensitive indicator of biological monitoring to assess environmental degradation. Copyright © 2001 John Wiley & Sons, Ltd.     

Predicting joint frequency distributions of depth and velocity for instream habitat assessment

Stream ecosystem structure and function are strongly influenced by patterns of velocity and depth. Simple methods for predicting the spatial distributions of these two variables, as functions of one‐dimensional reach and discharge characteristics, have been recently reported in the literature. These studies have provided valuable insight into the fundamental factors influencing stream behaviour and represent a practical alternative to multi‐dimensional hydrodynamic models. However, these previous studies have handled velocity and depth separately, while there is evidence that meso‐habitats and stream biota are associated with distinct combinations of the two variables. Therefore, we used survey data from 92 stream reaches in New Zealand to develop a model for the joint distribution of depth and velocity. We found that, for each reach, the bivariate distribution of relative velocity and relative depth could be described by a mixture of two end‐member distributions, one bivariate normal and the other bivariate lognormal, each with fixed parameters. The relative contribution of each shape for a particular reach at a particular discharge could then be related to the reach mean Froude number, the reach mean relative roughness, and the ratio of the survey discharge to the mean discharge. As these inputs can be readily estimated for changed channel morphology, our model should provide a useful approach for linking river rehabilitation strategies to hydraulics and ecology. Copyright © 2007 John Wiley & Sons, Ltd.     

Initial impact of the Gabčíkovo hydroelectric scheme on the species richness and composition of 0+ fish assemblages in the Slovak flood plain,River Danube

Relatively little information exists on the effects of hydroelectric schemes on 0+ fish composition in large European rivers because few or no pre‐impact data exist. We compared 0+ fish species richness and composition, relative density, fish size as well as available and used habitat using data from 12 floodplain sites sampled just prior to (1992) and four years after (1996) the start of operations of the Gab?íkovo hydropower station on the River Danube (Slovakia). We also used modelling techniques to assess the change in species richness and habitat use and to predict 1996 occurrences from the 1992 data set. The floodplain was greatly modified by the hydroscheme. Only 12 of 27 sites sampled in August 1992 were extant in August 1996. Therefore, all four channel types identified (flowing, abandoned, weir, wing‐dam) were more lentic in 1996 than in 1992, with increased width, smaller‐sized sediment (silt, clay) and greater amounts of macrophytes. After the operations of the hydroscheme, the overall relative density of fishes (individuals per surface area) of all ages decreased, with the exception of 0+ fishes, despite a slight reduction in 0+ fish density in all channel types except weirs. Species number increased from 25 to 28, although in all channel types there was a change in the composition of the 0+ fish assemblages, with rheophiles generally replaced by limnophiles and migrants from the lower Danube. The two most important microhabitat variables were the proportion of macrophytes and gravel, the latter being the factor distinguishing 0+ fish microhabitat use in 1992 (preferences) and 1996 (indifference or avoidance). Species richness and 0+ fish density in 1996 could be predicted from the 1992 data using simple log‐linear models (density, richness, sample number). Species‐specific occurrence in 1996 could not be predicted using environmental/fish data from 1992 with multiple regression or generalized additive models (GAM). However, the overall GAM from 1992 could predict overall fish occurrence in 1996. Copyright © 2003 John Wiley & Sons, Ltd.     

Hydrosedimentary classification of natural and engineered backwaters of a large river,the lower Rhône: possible applications for the maintenance of high fish biodiversity

At the end of the last century, the shorelines of the Lower River Rhône were embanked and submersible dikes were built in the main channel, delimiting dike fields. We compared the morphological, hydrological and sedimentary variables of nine dike fields, four sites in dead arms and one in the main channel, in order to describe the fluviosedimentary functioning and to produce a classification of these different natural and engineered backwaters. Within these ‘artificial floodplains’, the different types of backwaters and their long-term changes bear a strong similarity to those observed within a natural floodplain. The long-term frequency of submersion by the water of the main river channel is the first factor that controls the erosion and sedimentation within the different backwaters. Three types of site can be distinguished: the lotic sites are the main channel and one dike field, five dike fields comprise the semi-lotic sites and the cluster lentic sites include the three remaining dike fields and the four dead arms sites. These three groups also differ in their riparian habitats and in their juvenile fish assemblages. As juvenile fish were most abundant in the semi-lotic dike fields, the use of such structures can be envisaged in order to restore high fish diversity in rivers where the former floodplain has disappeared or is no longer accessible to fish because of human modifications. © 1997 John Wiley & Sons, Ltd.     

Changes to the trophic structure of a desert fish community following river regulation and species turnover: Implications for an endangered top predator

A poor understanding of factors leading to species decline can result in inefficient or ineffective species restoration. Endangered Colorado pikeminnow (Ptychocheilus lucius) was nearly extirpated from the San Juan River, NM, USA and recent efforts to reestablish the species via hatchery augmentation of juveniles has yet to reach the target number of adults in the system. To assess how changes to the river's food web could be limiting reestablishment of this top predator, we used stable isotope (δ¹³C and δ¹⁵N) signatures of the fish community pre- (museum specimens) and post river regulation with coincident extirpations and invasions. Following river regulation, four of five community-wide trophic structure metrics that quantify overall resource use were reduced and species turnover likely had little effect per se. For species sampled in both time periods, shared trophic resources generally increased (mean niche overlap = +35.7%). Additionally, Colorado pikeminnow experienced the largest decrease in niche breadth (−72%) and diet mixing models suggested a shift from piscivory towards insectivory in contemporary collections. Our results suggest an overall reduction in basal resource availability after river regulation. We propose increased reliance on similar resources may be limiting fish prey for Colorado pikeminnow, ultimately contributing to the slow and limited reestablishment in the San Juan River. This study adds to the growing body of knowledge provided by museum specimens and stable isotope analyses to identify food-web dynamics that are a departure from historical conditions, which can provide novel information critical to imperiled species management in modified systems.     

Linking a spatially explicit watershed model (SWAT) with an in‐stream fish habitat model (PHABSIM): A case study of setting minimum flows and levels in a low gradient,sub‐tropical river

As changes in landuse and the demand for water accelerate, regulators and resource managers are increasingly asked to evaluate water allocation against the need for protection of in‐stream habitat. In the United States, only a small number of river basins have the long‐term hydrograph data needed to make these assessments. This paper presents an example of how to bridge the conceptual and physical divide between GIS‐based watershed modelling of basin‐discharge and in‐stream hydraulic habitat models. Specifically, we used a Soil and Water Assessment Tool (SWAT) model for the Hillsborough River to produce data for use in a Physical HABitat SIMulation (PHABSIM) model of the same river. This coupling of models allowed us to develop long‐term discharge data in ungauged river systems based on watershed characteristics and precipitation records. However this approach is not without important limitations. Results confirm that accuracy of the SWAT‐predicted hydrograph declines significantly when either the DEM resolution becomes too coarse or if DEM data are resampled to a coarser or finer resolution. This is due to both changes in the size and shape of the river basin with the varying DEMs and subsequent shifts in the proportions of land use, soils and elevation. Results show the use of 30 m DEMs produced hydrographic patterns amenable for using in‐stream habitat protocols like PHABSIM model, especially where little or no hydrographic and land use information exists. Copyright © 2010 John Wiley & Sons, Ltd.