Changes In Physical Habitat Research Articles

A Bayesian analysis of physical habitat changes at tributary confluences in cobble‐bed upland streams of the Acheron River basin, Australia

Tributary confluences are known to affect downstream channel morphology and have the potential to increase downstream habitat heterogeneity. However, few studies have explicitly investigated the effect of tributaries on physical habitat. We used Bayesian modelling to investigate tributary effects on channel morphology, flow velocity, and bed particle size distribution at eight confluences in the Acheron River system in Victoria, Australia, under high‐flow and low‐flow conditions. Consistent tributary effects across sites and flow stages were a localized increase in channel depth at the confluence and a step increase in channel width in the postconfluence channel. Other tributary effects, such as increased or decreased flow velocity, the presence and placement of confluence bed forms (e.g., scours, pools, bars, and avalanche faces), and altered bed particle size distributions, varied between sites and flow conditions. These results provide evidence of changes to the physical habitat at confluences, which may affect stream biota.

Climate–ocean variability and Pacific hake: A geostatistical modeling approach

Climate forcing of the California Current has been known to impact the distribution and abundance of a number of local fish populations, but the mechanisms involved remain poorly understood. Climate metrics such as the Pacific Decadal Oscillation (PDO) and the El Niño Southern Oscillation (ENSO) are usually used to represent climate processes and direct links are made between climate forcing and production variability. This involves aggregation of impacts across large spatial scales and range of species. However, fluctuations in productivity are often the result of changes in physical habitat. In order to fully understand the relationship between climate and productivity, habitat changes should be addressed. In this study we use a geostatistical approach to quantify adult Pacific hake habitat during different climate regimes. Several authors have suggested that the distribution and intensity of the sub-surface poleward flow (the undercurrent) plays a key role in defining adult hake habitat along the west coast of North America. Here we build a model designed to predict hake habitat distribution in space based on sub-surface poleward flow distribution and bottom depth. Our results show that hake habitat expands in 1998 El Niño year compared to 1995. Given the important predatory role that hake plays in the CC, the amount and distribution of adult hake habitat has large implications for the Pacific Northwest food web and could thus serve as an ecosystem indicator representing important physical–biological interactions. Spatially based ecosystem indicators such as the one we develop here address two important yet neglected areas in the ‘Ecosystem Indicators debate’: the importance of developing metrics explicitly representing spatial and environmental processes shaping ecosystem structure. Without these, our power to fully describe ecosystems will be limited.

Fish habitat modelling as a tool for river management

This paper presents an integrated modelling approach to simulate and assess ecological effects of physical habitat changes in rivers. An ecohydraulic simulation tool was created by combining a 1D hydraulic model based on HEC-RAS software and the fish habitat module of CASiMiR, a fuzzy logic-based ecohydraulic modelling system. This tool was applied on a river stretch commonly occurring in Belgium and elsewhere in Europe. In particular the effect of weir removal on habitat suitability for bullhead ( Cottus gobio L.) was simulated. Physical conditions of the studied stretch after weir removal were simulated with a hydraulic model. CASiMiR linked these conditions to ecological expert knowledge to calculate habitat suitability for three life stages of bullhead at four different flow rates based on fuzzy logic. Results indicated that after weir removal, habitat suitability increased significantly for all life stages and all flow rates. The presented approach is promising regarding fish community assessment and ecological river engineering.

Effects of Urbanization on the Distribution and Abundance of Amphibians and Invasive Species in Southern California Streams

Abstract: Urbanization negatively affects natural ecosystems in many ways, and aquatic systems in particular. Urbanization is also cited as one of the potential contributors to recent dramatic declines in amphibian populations. From 2000 to 2002 we determined the distribution and abundance of native amphibians and exotic predators and characterized stream habitat and invertebrate communities in 35 streams in an urbanized landscape north of Los Angeles (U.S.A.). We measured watershed development as the percentage of area within each watershed occupied by urban land uses. Streams in more developed watersheds often had exotic crayfish (Procambarus clarkii) and fish, and had fewer native species such as California newts (Taricha torosa) and California treefrogs (Hyla cadaverina). These effects seemed particularly evident above 8% development, a result coincident with other urban stream studies that show negative impacts beginning at 10–15% urbanization. For Pacific treefrogs (H. regilla), the most widespread native amphibian, abundance was lower in the presence of exotic crayfish, although direct urbanization effects were not found. Benthic macroinvertebrate communities were also less diverse in urban streams, especially for sensitive species. Faunal community changes in urban streams may be related to changes in physical stream habitat, such as fewer pool and more run habitats and increased water depth and flow, leading to more permanent streams. Variation in stream permanence was particularly evident in 2002, a dry year when many natural streams were dry but urban streams were relatively unchanged. Urbanization has significantly altered stream habitat in this region and may enhance invasion by exotic species and negatively affect diversity and abundance of native amphibians.

Experimental reintroduction of woody debris on the Williams River, NSW: geomorphic and ecological responses

AbstractA total of 436 logs were used to create 20 engineered log jams (ELJs) in a 1.1 km reach of the Williams River, NSW, Australia, a gravel‐bed river that has been desnagged and had most of its riparian vegetation removed over the last 200 years. The experiment was designed to test the effectiveness of reintroducing woody debris (WD) as a means of improving channel stability and recreating habitat diversity. The study assessed geomorphic and ecological responses to introducing woody habitat by comparing paired test and control reaches. Channel characteristics (e.g. bedforms, bars, texture) within test and control reaches were assessed before and after wood placement to quantify the morphological variability induced by the ELJs in the test reach. Since construction in September 2000, the ELJs have been subjected to five overtopping flows, three of which were larger than the mean annual flood. A high‐resolution three‐dimensional survey of both reaches was completed after major bed‐mobilizing flows. Cumulative changes induced by consecutive floods were also assessed. After 12 months, the major geomorphologic changes in the test reach included an increase in pool and riffle area and pool depth; the addition of a pool–riffle sequence; an increase by 0.5–1 m in pool–riffle amplitude; a net gain of 40 m3 of sediment storage per 1000 m2 of channel area (while the control reach experienced a net loss of 15 m3/1000 m2 over the same period); and a substantial increase in the spatial complexity of bed‐material distribution. Fish assemblages in the test reach showed an increase in species richness and abundance, and reduced temporal variability compared to the reference reach, suggesting that the changes in physical habitat were beneficial to fish at the reach scale. Copyright © 2004 John Wiley & Sons, Ltd.

PHYSICAL HABITAT ASSESSMENT IN URBAN RIVERS UNDER FUTURE FLOW SCENARIOS

ABSTRACTRiver corridors in urban environments provide areas of biodiversity which are important for both aesthetic and economic reasons. A physical habitat model, which was used to assess urban rivers in Birmingham, UK, was applied to pairs of selected reaches to represent differing levels of habitat diversity on three rivers. The results for different life‐stages of dace, roach and chub suggest that the worst physical habitat occurs in highly modified channels and at the highest flows. Four scenarios, which were designed to represent alterations in flow regime caused by changes in management practices, were calculated using the hydrological model. Changes in physical habitat created by changes to the flow regime were assessed using a consistent, replicable method. It was shown that an increase in runoff would have detrimental effects in all cases, and that less engineered sites would benefit more from flow reductions. The lack of a suitable habitat for fry is shown to be a limiting factor for fish at all sites.

An assessment of water quality, physical habitat, and biological integrity of an urban stream in Wichita, Kansas, prior to restoration improvements (phase I).

Urban development alters the natural hydrological conditions of many streams and rivers often resulting in the degradation of water quality, physical habitat, and biotic integrity of lotic systems. Restoration projects attempt to improve and maintain the ecological integrity of urban streams; however, few projects have quantified improvements to stream ecology following implementation of restoration measures. This paper summarizes pre-restoration data collected as part of an urban stream restoration project on Gypsum Creek in Wichita, Kansas. Water quality monitoring revealed eutrophic conditions in the stream and the presence of pesticides. Channelization has led to changes in physical habitat including bank erosion, sedimentation, loss of substrate and channel diversity, elimination of in-stream aquatic habitat, removal of riparian vegetation, and decreased base flows. Benthic macroinvertebrate communities appear degraded with more than 90% of individuals collected described as tolerant to anthropogenic stressors. Fish communities were assessed with an Index of Biotic Integrity and were rated as poor to fair, with trophic structure dominated by generalists, no sensitive species present, and one-third of the species collected considered non-native. Overall, the data collected strongly suggest that site-specific restoration measures need to be implemented in order to improve and maintain the ecological condition of Gypsum Creek. Recommendations for improvements have been made to city managers, with implementation beginning in spring 2003 (dependent upon funding availability).

Habitat Associations of Fishes in the Devils River, Texas

ABSTRACT The Devils River is a spring-fed river that drains desert landscape in southern Texas and provides essential habitat for several endemic and threatened fish species. To evaluate potential effects of seasonal changes in physical habitat on fish distribution and abundance, we examined species-habitat associations in two reaches separated by 1.5 km. A distinct assemblage pattern existed in each of three mesohabitat types (pool, riffle, run). At the scale of stream reach, species distribution and abundance were associated more with factors related to geomorphology than physicochemistry. Similar mesohabitats had similar fish assemblages, irrespective of reach. Reaches and mesohabitats displayed seasonal variation in physicochemistry and fish assemblage structure. Assemblages associated with runs were least variable across seasons, however no species was strongly associated with runs. Because runs had comparatively little structural complexity and provided little protection from piscivorous smallmouth bass (Micropterus dolomieu), species probably use these areas primarily as migration corridors. Densities of two threatened species, Etheostoma grahami and Cyprinella proserpina, were negatively correlated with smallmouth bass density.

Factors regulating brown trout populations in two French rivers: application of a dynamic population model

AbstractA dynamic population model was developed to study the impact of biotic and abiotic environmental factors on changes in trout populations. The model is based on the Leslie Matrix and simulates population change by age class in terms of biological parameters (i.e. fish survival, fertility, growth rates), which are dependent on environmental conditions. Changes in physical habitat, expressed as Weighted Usable Area, cause displacement of fish and increased mortality. Calculations were made at 1‐month intervals to account for the effect of climatic variations on the population.The model was used to analyze the dynamics of two trout populations, quite different in terms of their biological characteristics: one in Lower Normandy in the Oir watershed and the other in the Pyrenees Mountains in the Neste d'Oueil watershed. Application of the model to those populations revealed two types of stabilizing mechanisms. The first was a capacity for population restoration, which is well‐represented by the model through the phenomenon of density‐dependent mortality in the first months of life. The second was adjustment of the adult population to the carrying capacity of the environment.The two applications demonstrate the utility of this type of model for understanding and simulating the dynamics of different cohorts of a population. Coupling habitat models and dynamic population models facilitates the identification of key periods during which carrying capacity—related to the hydrology—becomes a limiting factor for fish. This brings new perspectives to water management and may facilitate analysis of instream flow requirements related to water development projects, such as hydropower plants. Copyright © 2001 John Wiley & Sons, Ltd.

Applicability of NASQAN data for ecosystem assessments on the Missouri River

AbstractThe effectiveness of ecological restoration efforts on large developed rivers is often unknown because comprehensive ecological monitoring programs are often absent. Although Eulerian water‐quality monitoring programs, such as the National Stream Quality Accounting Network (NASQAN) program, are more common, they are usually not designed for ecological assessment. Therefore, this paper addresses the value of NASQAN for ecological assessments on the Missouri River and identifies potential program additions and modifications to assess certain ecological changes in physical habitat, biological structure and function, and ecotoxicity.Five additional sites; the analysis of chlorophyll, mercury, ATP, potential endocrine disruptors, total trace elements, and selected total hydrophobic organics; and the hourly measurement of dissolved oxygen, turbidity, and temperature are recommended. Hourly measurements would require an entirely new operational aspect to NASQAN. However, the presence of data loggers and satellite transmitters in the gauging stations at all NASQAN sites substantially improves the feasibility of continuous water‐quality monitoring. The use of semipermeable membrane devices (SPMDs) to monitor dissolved bioaccumulating organics and trace elements, identification and enumeration of zooplankton, and characterization of the bioavailability of organic matter are also recommended.The effect of biological processes on the conservative assumptions that are used in flux and source determinations of NASQAN constituents are also evaluated. Organic carbon, organic nitrogen, dissolved phosphate, and dissolved inorganic nitrogen are the NASQAN constituents most vulnerable to biological processes and thus violation of conservative assumptions. Published in 2001 by John Wiley & Sons, Ltd.

Tributaries, sediment sources, and the longitudinal organisation of macroinvertebrate fauna along river systems

Tributary confluences are sites along a main channel where, because of the introduction of water and (or) sediment, the water volume, bed sediment character, and water quality of the mainstream can change abruptly. These shifts ensure that abiotic gradients seldom vary smoothly or continuously for distances of more than 100–102km along any river system. The ways in which tributaries and related sediment recruitment points structure longitudinal changes in physical habitat are examined. Variables of importance to stream biota are affected and, in turn, it is suggested that the arrangement of tributaries and related features is an important control on the longitudinal organisation of macroinvertebrate benthos at moderate spatial scales. A new model is presented that stresses the importance of hydrological and sedimentological networks for organising lotic fauna. The link discontinuity concept emphasises the discontinuous nature of lotic ecosystem gradients, addresses the importance of tributaries in unregulated as well as regulated rivers, and extends, to its logical conclusion, the limited recognition of tributary influence in the river continuum concept. A case study from British Columbia, Canada, illustrates the general merit of the new model.

Mechanisms of maintenance of tropical freshwater fish communities in the face of disturbance.

Community resistance to, and resilience from, perturbation will determine the trajectory of recovery from disturbance. Although selective timber extraction is considered a severe disturbance, fish communities from headwater streams around Danum Valley Field Centre, Sabah, Malaysia, showed few long-term changes in species composition or abundance. However, some species showed short-term (< 18 months) absence or decrease in abundance. These observations suggested that both resistance and resilience were important in maintaining long-term fish community structure. Resistance to perturbation was tested by monitoring fish communities before and after the creation of log-debris dams, while resilience was investigated by following the time-course of recolonization following complete removal of all fish. High community resistance was generally shown although the response was site-specific, dependent on the composition of the starting community, the size of the stream and physical habitat changes. High resilience was demonstrated in all recolonization experiments with strong correlations between pre- and post-defaunation communities, although there was a significant difference between pool and riffle habitats in the time-course of recovery. These differences can be explained by the movement characteristics of the species found in the different habitats. Resilience appeared to be a more predictable characteristic of the community than resistance and the implications of this for ensuring the long-term persistence of fish in the area are discussed.

ADDITION OF SPURS TO STONE TOE PROTECTION FOR WARMWATER FISH HABITAT REHABILITATION1

ABSTRACT: Longitudinal stone toe is one of the most reliable and economically attractive approaches for stabilizing eroding banks in incised channels. However, aquatic habitat provided by stone toe is inferior to that provided by spur dikes. In order to test a design that combined features of stone toe and spurs, eleven stone spurs were placed perpendicular to 170 m of existing stone toe in Goodwin Creek, Mississippi, and willow posts were planted in the sandbar on the opposite bank. Response was evaluated by monitoring fish and habitats in the treated reach and an adjacent comparison reach (willow post planting and standard toe without spurs) for four years. Furthermore, physical habitats within the treated reach were compared with seven reaches protected with standard toe on a single date three years after construction. Overall results indicated that spur addition resulted in modest increases in baseflow stony bankline, water width and pool habitat availability, but had only local effects on depth. These relatively small changes in physical habitat were exaggerated seasonally by beaver dams that appeared during periods of prolonged low flow in late Summer and Autumn. Physical changes were accompanied by shifts in fish species composition away from a run‐dwelling assemblage dominated by large numbers of cyprinids and immature centrarchids toward an assemblage containing fewer and larger centrarchids. Biological responses were at least partially due to the effects of temporary beaver dams.

Individual-based model of sympatric populations of brown and rainbow trout for instream flow assessment: model description and calibration

This paper describes an individual-based model of sympatric populations of brown and rainbow trout in a stream habitat. The model provides a tool for projecting flow and temperature effects on trout populations by linking the hydraulic component of the instream flow incremental methodology/physical habitat simulation system (IFIM/PHABSIM) to an individual-based population model. PHABSIM simulates the spatial distribution of depth and velocity at different flows, and indirectly, the availability of spawning habitat, cover and feeding station. The individual-based model simulates reproduction, growth and mortality of individual trout as a function of flow and temperature. Population dynamics arise from the survival and reproduction of individual trout. The spatially explicit nature of the model permits evaluation of behavioral responses used by fish to changes in physical habitat. The model has been calibrated to a stream segment in the North Fork Middle Fork Tule River, California. Selected parameters were adjusted to calibrate the model for length and abundance (including production of a new year class) at the end of 1-year simulations for each of 9 years. Predicted and observed lengths were in good agreement, although neither varied appreciably among years. Predicted and observed abundances were not in as good agreement, and differed considerably for some years. These differences reflect a combination of uncertainties in the field data and uncertainties in the model structure and parameter values. Fifty-year simulations indicated that model projections of length and abundance were stationary, although abundance values fluctuated considerably. Seven advantages for using simulation models of this type are emphasized. How to most effectively interpret results from such simulation models as part of instream flow environmental assessments remains a challenge. Variability and uncertainty in both field data and replicate model simulations are realities that have implications for scientists, resource managers, and regulators in projecting growth and abundance responses of fish populations to alternative flow or temperature regimes.

Lateral migration of fishes in Amazon floodplains

Abstract— Migrations of fish in the outlet channel of Lago do Rei, a floodplain lake on Careiro Island in the Amazon River, were examined using three capture methods. Of the 85 species found in the Parana do Rei (channel), 20 migrated between the lake and river. Migrations from the lake to the river occurred in two pulses. In August‐September, as the river water level began to recede, some fish migrated to the river with the current. As the river water level rose in December‐January, additional fish migrated towards the main river against the current. Fish returned to the lake by March or April after they had spawned. The migratory patterns of six species, family Curimatidae and Prochilodontidae: Potamorhina latior, Psectrogaster amazonica, P. rutiloides, Curimata kneri, Prochilodus nigricans and Semaprochilodus taeniurus are described in detail. Lateral migrations of fish in this ecosystem appear to be closely linked to breeding and to physical habitat changes related to river water level.

Physical habitat changes and macroinvertebrate response to river regulation: The river Rede, UK

AbstractDownstream variations of benthic macroinvertebrate communities on the River Rede below Catcleugh Reservoir, impounded in 1905, are related to a simple index of regulation magnitude, related to hydrological, water quality and trophic changes, and variations of channel morphology. The river is divided into five sectors on the basis of network morphometry and channel form. Channel change to flow regulation is confined to a short (1.6 km) reach immediately below the dam within which channel width and conveyance have been reduced by 53 and 75%, respectively. Downstream, siltation has occurred, but it is patchy and average levels of sediment finer than 2 mm are less than 10%. The main faunal responses — increased abundance and number of taxa — are also confined to the first sector below the dam. Ephemeroptera are shown to be the best describers of the downstream pattern. Variations of the fauna between riffles within sectors are shown to relate to site‐specific hydraulic conditions, especially bed shear stress.

Measures of marine environmental quality

In the past, measures of marine environmental quality have focused on effects of specific stressors on ecosystem components—biochemical, genetic, physiological, pathological, behavioural and community. To measure ecosystem changes resulting from multiple stresses, such as a combination of pollutants (some local and some not) and physical habitat changes including those that might arise from global warming, it is necessary to measure attributes of whole ecosystems. These include primary productivity, nutrient cycling, species diversity, instability, disease prevalence, size spectrum and contaminant effects across trophic levels. Monitoring programmes should test hypotheses regarding changes in and effects on (a) processes, such as bioaccumulation, biomass production, respiration, reproduction and eutrophication that, if impaired, may lead to changes in ecosystem structure; and (b) the structure and key system attributes of marine ecosystems.

Notes on contents

This paper describes an individual-based model of sympatric populations of brown and rainbow trout in a stream habitat. The model provides a tool for projecting flow and temperature effects on trout populations by linking the hydraulic component of the instream flow incremental methodology/physical habitat simulation system (IFIM/PHABSIM) to an individual-based population model. PHABSIM simulates the spatial distribution of depth and velocity at different flows, and indirectly, the availability of spawning habitat, cover and feeding station. The individual-based model simulates reproduction, growth and mortality of individual trout as a function of flow and temperature. Population dynamics arise from the survival and reproduction of individual trout. The spatially explicit nature of the model permits evaluation of behavioral responses used by fish to changes in physical habitat. The model has been calibrated to a stream segment in the North Fork Middle Fork Tule River, California. Selected parameters were adjusted to calibrate the model for length and abundance (including production of a new year class) at the end of 1-year simulations for each of 9 years. Predicted and observed lengths were in good agreement, although neither varied appreciably among years. Predicted and observed abundances were not in as good agreement, and differed considerably for some years. These differences reflect a combination of uncertainties in the field data and uncertainties in the model structure and parameter values. Fifty-year simulations indicated that model projections of length and abundance were stationary, although abundance values fluctuated considerably. Seven advantages for using simulation models of this type are emphasized. How to most effectively interpret results from such simulation models as part of instream flow environmental assessments remains a challenge. Variability and uncertainty in both field data and replicate model simulations are realities that have implications for scientists, resource managers, and regulators in projecting growth and abundance responses of fish populations to alternative flow or temperature regimes.