Species’ distributions are influenced by abiotic and biotic factors but direct comparison of their relative importance is difficult, particularly when working with complex, multi-species datasets. Here, we present a flexible method to compare abiotic and biotic influences at common scales. First, data representing abiotic and biotic factors are collected using a combination of geographic information system, remotely sensed, and species’ functional trait data. Next, the relative influences of each predictor variable on the occurrence of a focal species are compared. Specifically, ‘sample’ data from sites of known occurrence are compared with ‘background’ data (i.e. pseudo-absence data collected at sites where occurrence is unknown, combined with sample data). Predictor variables that may have the strongest influence on the focal species are identified as those where sample data are clearly distinct from the corresponding background distribution. To demonstrate the method, effects of hydrology, physical habitat, and co-occurring fish functional traits are assessed relative to the contemporary (1950 – 1990) distribution of the American Eel (Anguilla rostrata) in six Mid-Atlantic (USA) rivers. We find that Eel distribution has likely been influenced by the functional characteristics of co-occurring fishes and by local dam density, but not by other physical habitat or hydrologic factors.

This thesis examines the influence of large woody debris (LWD) on the physical habitat of British headwater streams. The distribution and density of LWD accumulations throughout catchments is considered using data from the River Habitat Survey (RHS) and more detailed catchment scale surveys. The effect of accumulations of LWD on stream hydraulics and physical habitat at a reach scale is examined using transect based measurements of depth and velocity over a range of discharges before and after LWD removal for two reaches, measurement of reach average hydraulic parameters for 25 reaches with differing levels of LWD and the application of the Aggregated Dead Zone (ADZ) and Physical Habitat Simulation (PHABSIM) models. The RHS and catchment scale surveys showed that LWD accumulations exhibit systematic patterns in abundance within catchments, smaller streams having a higher density of LWD and a greater number of LWD accumulations. The most hydraulically active type of LWD accumulations were found to reduce flow velocity by an average of 55%, increase channel roughness by 149% and increase depth by 165%. This impact was, however, found to vary with discharge. Application of the Aggregated Dead Zone (ADZ) model showed that LWD increases the volume of ADZ, which may indicate greater ecological refuge potential. Using the Physical Habitat Simulation (PHABSIM) model, it was found that LWD improved habitat quality and overall habitat diversity.

Abstract The subject of the study was to search and test restoration measures for the most common physical habitat degradations in Finnish rivers. Methods for constructing nursery and spawning habitats for salmonid fishes were tested in small rivers dredged for timber floating in the Iijoki watercourse. Physical habitat modelling was used to simulate the effects of restoration measures to the hydro-physical conditions and potential fish habitats. The rehabilitation of the river bed and the placement of boulder structures, especially large boulder dams, made the rapids spatially more complex and increased the availability of potential physical habitat for brown trout (Salmo trutta). The physical habitat model was applied in the river Siikajoki to estimate the impacts of flow regulation patterns on the physical habitat quality. No single flow event causing a bottle-neck effect on the potential habitat suitable for brown trout was found. In a sensitivity analysis of habitat modelling, modifications of the suitability criteria appeared to have a major influence on habitat suitability for young brown trout. The applicability of low reefs and narrow side channels for fish habitat improvement was studied, using the large river impoundment of Oulujoki as a test area. Limited validation experiments of the model results were carried out on the basis of fish telemetry experiments and observations by local rod fishermen. The restoration measures appeared to diversify the channel structure and increase sheltered lateral habitats for grayling (Thymallus thymallus). Habitat structure and fish populations of seven small forest streams and two modified streams were surveyed using visual evaluation and electrofishing studies. None of the studied streams was found to be in pristine condition in all of its reaches. Brown trout was the most abundant species in most of the study streams. In most streams the brown trout distribution correlated positively with substrate size. The accumulation of fine materials on the stream bottom due to forestry operations was estimated to be the most harmful human impact on the studied streams. Some restoration suggestions were made for each of the streams.

Abstract The degradation of rivers and streams has led to world-wide efforts to restore freshwater habitats. A good understanding of the social-ecological context is considered key to successful restoration. In this thesis, a multidisciplinary framework was applied to study ecological and social dimensions of restoration success. First, the long-term performance of in-stream restoration measures was examined by conducting repeated cross-sectional surveys in restored streams up to 20 years post-restoration. Next, nationwide electrofishing data were used to assess the density responses of juvenile salmonids to habitat restoration and factors influencing restoration success were examined. Finally, changes in the provision of ecosystem services were evaluated by comparing the perceptions of restoration outcomes between two user groups and three study rivers. The results indicated that the restoration-induced increase in habitat heterogeneity persisted over time, initiating an overall positive development also in biological metrics (i.e. juvenile salmonids and aquatic mosses). However, overall substrate variability in restored streams remained lower than in near-pristine streams, with a shortage of gravel beds. Fish responses varied strongly between rivers, which was explained mainly by watershed scale (e.g. river basin size, dominant geology) and local (potential interspecific competition) factors. Site-specific differences were also observed in the delivery of ecosystem services, mainly reflecting stakeholder perceptions of landscape value and fish provisioning. Overall, the results show that setting indicators and target levels for restoration success is grounded on perspective. Socially conscious ecological restoration that acknowledges local specialities and needs in priority setting, planning and implementation has the potential to provide multiple benefits for river ecosystems and society. / Tiivistelmä Virtavesien ekologisen tilan heikentyminen on johtanut maailmanlaajuisiin toimiin niiden elinympäristöjen kunnostamiseksi. Usein ekologisen kunnostuksen onnistuminen edellyttää kuitenkin ihmisen ja ympäristön vuorovaikutussuhteiden laaja-alaista ymmärtämistä. Tässä väitöskirjatutkimuksessa käytettiin monitieteistä viitekehystä virtavesikunnostusten ekologisten ja sosiaalisten vaikutusten tutkimiseen. Ensimmäisessä osatyössä arvioitiin kunnostustoimenpiteiden kestävyyttä sekä uoman rakenteellisen monimuotoisuuden kehittymistä pitkällä aikavälillä (10-20 vuotta kunnostusten jälkeen). Toisessa osatyössä tehtiin valtakunnallisen sähkökalastusaineiston avulla meta-analyysipohjainen yhteenveto suomalaisten virtavesikunnostusten vaikutuksista taimenen ja lohen kesänvanhojen (0+) poikasten tiheyteen sekä tutkittiin kunnostustulokseen vaikuttavia ympäristötekijöitä. Kolmannessa osatyössä selvitettiin kunnostusten onnistumista ekosysteemipalvelujen näkökulmasta vertaamalla kahden eri käyttäjäryhmän kokemia muutoksia kolmen tutkimusjoen välillä. Väitöskirjan tulokset osoittivat, että kunnostukset lisäsivät jokiuoman rakenteellista monimuotoisuutta sekä lyhyellä että pitkällä aikavälillä ja vaikuttivat myönteisesti myös biologisiin indikaattoreihin (lohikalojen poikastiheys ja vesisammalet). Vaihtelu pohjan laadussa oli kuitenkin luonnontilaisia uomia vähäisempää ja erityisesti kutuun soveltuvaa soraa oli niukasti. Lohikalojen tiheysvaste vaihteli voimakkaasti jokien välillä, mikä selittyi pääasiassa valuma-alueeseen liittyvillä (esim. valuma-alueen koko ja geologia) ja paikallisilla (mahdollinen lajien välinen kilpailu) tekijöillä. Paikkasidonnaisia eroja havaittiin myös vaikutuksissa ekosysteemipalveluihin ja ne heijastivat etenkin maisemassa ja kalasaaliissa koettuja muutoksia. Tutkimus osoitti, että erilaiset taustat ja odotukset vaikuttavat vahvasti siihen, millaisten kriteerien perusteella kunnostusten onnistumista arvioidaan. Jotta kunnostuksilla saavutettaisiin hyötyjä sekä jokiekosysteemeille että yhteiskunnalle, on tärkeää tuntea paikalliset erityispiirteet ja -tarpeet ja ottaa ne huomioon kunnostuskohteiden valinnassa sekä toimenpiteiden suunnittelussa ja toteutuksessa.

No description available.

High-resolution velocity measurements were undertaken over a series of redds and riffles on a gravel-bed stream to quantify the hydrodynamics preferred by spawning brown trout (Salmo trutta) and rainbow trout (Oncorhynchus mykiss) for redd-site selection. On each riffle studied, over 6,000 velocity measurements per day were acquired to quantify the velocity, depth, Reynolds number, Froude number, bed shear, and turbulent kinetic energy per unit area of streambed in attempts to relate fluid properties to redd-site selection, relative to remaining riffle structures. Results showed that velocity, Reynolds number, and Froude number vary widely at the redd- and riffle-scale with no apparent correlation to spawning location preference. Turbulent kinetic energy per unit area consistently demonstrated a strong correlation with redd locations whereby the metric maintained low values (i.e., unidirectional flow with little turbulence) where redds and attempted redds were observed. Habitat suitability indices were applied at the reach-, riffle-, and redd-scale using the results of the high-resolution velocity measurements. Findings demonstrated that habitat suitability indices, which are based on reach-scale hydraulics, were adequately represented at the reach scale. However, by decreasing the scale to the riffle- or redd-scale, where increasing heterogeneity in the flow regime is revealed, habitat suitability indices failed to adequately reflect the habitat conditions preferred by the spawning fish.

High-resolution velocity measurements were undertaken over a series of redds and riffles on a gravel-bed stream to quantify the hydrodynamics preferred by spawning brown trout (Salmo trutta) and rainbow trout (Oncorhynchus mykiss) for redd-site selection. On each riffle studied, over 6,000 velocity measurements per day were acquired to quantify the velocity, depth, Reynolds number, Froude number, bed shear, and turbulent kinetic energy per unit area of streambed in attempts to relate fluid properties to redd-site selection, relative to remaining riffle structures. Results showed that velocity, Reynolds number, and Froude number vary widely at the redd- and riffle-scale with no apparent correlation to spawning location preference. Turbulent kinetic energy per unit area consistently demonstrated a strong correlation with redd locations whereby the metric maintained low values (i.e., unidirectional flow with little turbulence) where redds and attempted redds were observed. Habitat suitability indices were applied at the reach-, riffle-, and redd-scale using the results of the high-resolution velocity measurements. Findings demonstrated that habitat suitability indices, which are based on reach-scale hydraulics, were adequately represented at the reach scale. However, by decreasing the scale to the riffle- or redd-scale, where increasing heterogeneity in the flow regime is revealed, habitat suitability indices failed to adequately reflect the habitat conditions preferred by the spawning fish.

Large woody debris (LWD) was added to North Fork Stony Creek and North Prong Barbours Creek in southwest Virginia to inlprove fish habitat. The purposes of this study were to monitor stream channel response to the addition of LWD at a stream reach scale and at a local scale around individual logs, to evaluate changes in fish population parameters, and to observe microhabitat availability and use before and after L WD additions. In low-gradient Stony Creek, LWD was effective in modifying fish habitat through the formation of pools, the structuring of poo1/riffle sequences, and the enhancement of channel complexity. New pools formed from the break up of continuous rime habitat, increasing the overall number of habitat units and decreasing mean surface areas. Total pool area increased for both treatment sections, while changing little in the reference section where no logs were added. Localized scour and fill was observed for crosssectional transects around individual logs, creating a more heterogenous environment than in areas without logs. In contrast, physical habitat changed little in moderate-gradient Barbours Creek after L WD was added. An increase in the relative weight of brook trout in Barbours Creek suggested that although minimal channel changes were observed, logs may have increased channel complexity and cover, providing resting areas of lower velocities next to food pathways, which may have lead to decreased energy expenditure. Observations of microhabitat use revealed that unlike adult brook trout, juvenile brook trout used a limited range of depths and velocities. Adult brook trout shifted microhabitat use in response to changes in microhabitat available. Low numbers of fish in Stony Creek may have been related to low pH, but numbers of adult brook trout found in each section increased in 1994. With improved water quality, I believe that fish abundance in Stony Creek would increase through time because of the improved habitat. Although few significant changes were observed for available microhabitat in Stony Creek, changes in physical habitat suggest that over time shifts in microhabitat would be apparent. / Master of Science

In 2000 the European Union introduced the Water Framework Directive, new legislation that regulates the use of surface waters within the European Community. The goal of this legislation is to protect, enhance and restore all surface waters within the Community to Good Surface Water Status. Good-Status is described as having low levels of anthropogenic distortion in its hydro-morphological and physiochemical components as well as possessing biota that would normally be associated with the type-specific aquatic ecosystem. The assessment of ecosystem status is to be defined by comparisons with intact representative reference sites, by using modelling techniques that define reference conditions, a combination of the two, or expert judgement. As undisturbed aquatic ecosystems are rare or non-existent in Europe the base-line data will have to be defined using the latter methodologies. The aim of this project is to help define reference conditions for lotic systems in Europe based on the physical instream habitat parameters of a resident species. Brown trout (Salmo trutta), a ubiquitous and well studies species endemic to Europe, was used as the target organism to develop the assessment protocol. The project focused on the requirements this species has of aspects of its physical habitat; specifically, its usage of depth, velocity, and substrate. An extensive survey of the scientific literature was used to define the requirements trout has for the three physical parameters at four life stages. These are the spawning, nursery, juvenile and adult-resident life stages. These requirements were expressed as tolerance profiles, which defined suitable, usable and not-suitable habitat. The methodology was demonstrated by evaluating the physical habitat available at six reaches in three small streams, March, Burnhouse and Bin Burns, which drain into the Carron Valley Reservoir in central Scotland. From the perspective of water depth, these streams seem best suited as nursery areas, are less well suited as juvenile habitat, and do not appear to be well matched for adult residents. The assessment of both velocity and substrate indicated that the portion of the study reaches available for use by resident brown trout increased with trout size. The assessment of all three physical habitat parameters at all study reaches found variable portions of the streams suitable for use by spawning trout. When the habitat variables are integrated all stream segments streams seem best suited as nursery and spawning areas. To a lesser extent juvenile trout can use these burns and very little habitat is available for use by adult resident trout. The tolerance profiles that were created in this study are standardized assessment criteria that when compared with stream survey data can produce an appraisal of habitat availability in any fluvial freshwater system that supports populations of brown trout (Salmo trutta). The assessment method can be combined to produce an integrated habitat assessment, using both an index and by the calculation of Froude number, which is a more realistic approach than the assessment of individual habitat parameters as salmonids choose their microhabitat based on multiple factors. This approach allows an investigator to determine the amount and relative portion of useable habitat and to determine the quality of that habitat. Finally, by examining the physical habitat variable that most strongly correlates with the final integrated habitat distribution the individual habitat parameter that is most important to the distribution of physical habitat at a site can be determined. While this technique would certainly benefit from further development it does show potential to aid in physical habitat assessment of trout streams.

In the past century, hydropower development in Sweden has been facilitated by the lack of appropriate environmental legislation. This exploitation has resulted in the current poor ecological status of most Swedish water bodies affected by hydropower, and in the need for new policies that reflect the 2000 European Water Framework Directive. Thus, the Swedish Agency for Marine and Water management (SwAM), the Swedish Energy Agency (SEA) and Svenska Kraftnät have elaborated a new national plan for the revision of almost all hydropower licenses in the next 20 years, and Vattenkraftens Miljöfond has carried out a pilot project on Ljungan river, to test different working methods for regional collaboration, and to find effective solutions for achieving the greatest possible benefit for the aquatic environment, while ensuring an efficient national hydropower supply. This thesis focuses on the fish habitat rehabilitation of a portion of Ljungan river highly affected by hydropower practices. By combining a 1D/2D hydraulic model, calibrated and validated, with a habitat model that defines the hydraulic preferences of the target fish species, it was possible to run different simulations and to quantify the optimal habitat obtainable in each scenario, following the PHABSIM methodology. The outputs of this analysis were produced in the form of Composite Suitability Index (CSI) maps and Weighted Usable Area (WUA)­discharge curves. The former resulted to be a very useful tool for analyzing the spatial distribution of suitable habitats for certain ecological processes, and for planning in­stream habitat improvement measures, while the latter have been efficiently used to identify and quantify the maximum habitat improvement achievable with the different mitigation scenarios. This approach helped to firstly assess the habitat improvement that would result from removing the weirs located along the river, leading to the conclusion that the removal would be effective only if combined with other morphological changes of the river channel. Additionally, the coupled eco­hydraulic model has been useful for the design of ecological flow scenarios able to achieve different levels of habitat improvement, including scenarios aimed at minimizing energy production losses. The use of the PHABSIM methodology resulted to be very suitable for the scale and scope of the project. However, it also required to limit the iii ecological drivers considered in the analysis and to make some simplistic assumptions about target species behavior, which must always be underlined and acknowledged when using the results in decision­making processes. / Under det senaste århundradet har vattenkraftsutbyggnaden i Sverige underlättats av bristen på lämplig miljölagstiftning. Detta utnyttjande har lett till att de flesta svenska vattenförekomster har en dålig ekologisk status och att det behövs en ny politik som återspeglar det europeiska ramdirektivet för vatten från 2000. Således har Havs­ och vattenmyndigheten, Energimyndigheten och Svenska Kraftnät utarbetat en ny nationell plan för översyn av nästan alla vattenkraftslicenser under de kommande 20 åren, och Vattenkraftens Miljöfond har genomfört ett pilotprojekt i Ljungan älv för att testa olika arbetsmetoder för regionalt samarbete och hitta effektiva lösningar för att uppnå största möjliga nytta för vattenmiljön samtidigt som man säkerställer en effektiv nationell vattenkraftförsörjning. Denna avhandling fokuserar på återställandet av fiskhabitatet i en del av Ljungan älven som är starkt påverkad av vattenkraftsutövning. Genom att kombinera en 1D/2D hydraulisk modell, kalibrerad och validerad, med en habitatmodell som definierar målfiskarternas hydrauliska preferenser var det möjligt att göra olika simuleringar och kvantifiera den optimala livsmiljö som kan erhållas i varje scenario, enligt PHABSIM­metodiken. Detta tillvägagångssätt har använts för att först och främst bedöma den förbättring av livsmiljön som skulle bli resultatet av att ta bort de dammar som finns längs älvsträckan, vilket ledde till slutsatsen att avlägsnandet skulle vara effektivt endast om det kombineras med andra morfologiska förändringar av flodfåran. Dessutom har den kopplade ekohydrauliska modellen varit användbar för att utform ekologiska flödesscenarier som kan uppnå olika nivåer av habitatförbättring, inklusive scenarier som syftar till att minimera förlusterna i energiproduktionen.