Riverine physical habitats and habitat utilization by fish have often been studied independently. Varying flows modify habitat composition and connectivity within a stream but its influence on habitat use is not well understood. This study examined brown trout (Salmo trutta) and bullhead (Cottus gobio) utilization of physical habitats that vary with flow in terms of size and type, persistence or duration, and frequency of change from one state to another, by comparing groundwater-dominated sites on the River Tern (Shropshire) with surface runoff-dominated lowland, riffle-pool sites on the Dowles Brook (Worcestershire). Mesohabitat surveys carried out at two-month intervals on a groundwater-dominated stream and on a surface runoff-influenced stream showed differences in habitat composition and diversity between the two types of rivers. The temporal variability in mesohabitat composition was also shown to differ between the two flow regime types. In the groundwater-influenced stream, mesohabitat composition hardly varied between flows whereas in the flashy stream it varied to a great extent with discharge. Habitat suitability curves for brown trout and bullhead were constructed to predict the potential location of the fish according to flow. The resulting prediction maps were tested in the field during fish surveys using direct underwater observation (snorkelling). Under the groundwater-influenced flow regime brown trout displayed a constant pattern of mesohabitat use over flows. Mesohabitats with non-varying characteristics over flows and with permanent features such as large woody debris, macrophytes or any feature providing shelter and food were favoured. Biological processes, such as hierarchy, life cycle and life stage appeared to play a key role in determining fish habitat use and to a greater extent than physical processes in these streams. Bullhead observations in the flashy river showed that mesohabitat use varied with flow but that some mesohabitats were always favoured in the stream. Pools and glides were the most commonly used mesohabitat, due to their stability over flows and their role as shelter from harsh hydraulic conditions and as food retention zones. The presence of cobbles was also found to be determinant in bullhead choice of habitat. In this flashy environment, physical processes such as flow and depth and velocity conditions appeared to be a more decisive factor in bullhead strategy of habitat use than biological processes. This research shows that: 1. Though differences in habitat use strategies between the two flow regimes can in part be attributed to differing ecology between the species, flow variability affects fish behaviour. 2. A stable flow regime allows biological processes to be the main driving force in determining fishbehaviour and location. A highly variable environment requires fish to develop behaviour strategies in response to variations in hydraulic conditions, such as depth and velocity, which constitute the key factor in determining fish location.

Thesis (Ph. D. (Zoology)) -- University of Limpopo, 2009. / Aspects of the ecology and biology of the Lowveld largescale yellowfish (Labeobarbus marequensis) were studied in the Luvuvhu River over a period of three years. In this study the origin of the species, its phylogenetic relation to the other South African yellowfish species, its distribution and gross morphology are discussed and the lack of knowledge regarding aspects of the species is pointed out. The study area is identified and its geology, hydrology, climate and water quality as well as the historic distribution of the species is discussed. Adapted “truss” techniques were applied to measure and calculate the morphometric features related to feeding and habitat preference of the species. From this data the habitat preferences and requirements were inferred after which it was compared to data obtained during field surveys. The study of the breeding biology and ecology of the species included investigations of gonad and egg structure and development as well as seasonal surveys of selected breeding sites. The diet of the species was established through stomach content analyses and related to the digestive tract morphology. Data obtained from the Xikundu fishway was used to establish the migratory behaviour. Results show that nine distinct stanzas or growth phases, each with its own morphometric characteristics, were identified. The body form, and some morphological aspects, of the species make it suitable to cope with flowing water. Ontogenetic changes in body form and the identified morphological aspects were observed and related to the habitat preferences of the stanzas. A distinct ontogenetic shift in preferred habitat was illustrated. The species was shown to be fractional spawner with two spawning events per annum. A major extended spawning event occurred during spring or early summer and coincided with a temperature increase and in particular with an increase in flow. Breeding occurred at sites with fast flowing water over cobble or boulder beds and it was observed that the presence of nursery areas related to breeding biotopes was extremely important. Although the diet of the species was dominated by plant and algal matter, juvenile stanzas ingested large amounts of animal material. It was found that the spatial movements of the species could be characterised as migrations and that breeding and dispersal migrations occurred.

[Truncated abstract] Spatially explicit marine habitat data is required for effective resource planning and management across large areas, although mapped boundaries typically lack rigour in explaining what factors influence habitat distributions. Accurate, quantitative methods are needed. In this thesis I aimed to assess the utility of ecological models to determine what factors limit the spatial extent of marine habitats. I assessed what types of modeling methods were able to produce the most accurate predictions and what influenced model results. To achieve this, initially a broad scale marine habitat survey was undertaken in the Recherche Archipelago, on the south coast of Western Australia using video and sidescan sonar. Broad and more detailed functional habitats types were mapped for 1054km2 of the Archipelago. Broad habitats included high and low profile reefs, sand, seagrass and extensive rhodolith beds, although considerable variation could be identified from video within these broad types. Different densities of seagrass were identified and reefs were dominated by macroalgae, filter feeder communities, or a combination of both. Geophysical characteristics (depth, substrate, relief) and dominant benthic biota were recorded and then modelled using decision trees and a combination of generalised additive models (GAMs) and generalised linear models (GLMs) to determine the factors influencing broad and functional habitat variation. Models were developed for the entire Archipelago (n=2769) and a subset of data in Esperance Bay (n=797), which included exposure to wave conditions (mean maximum wave height and mean maximum shear stress) calculated from oceanographic models. Additional distance variables from the mainland and islands were also derived and used as model inputs for both datasets. Model performance varied across habitats, with no one method better than the other in terms of overall model accuracy for each habitat type, although prevalent classes (>20%) such as high profile reefs with macroalgae and dense seagrass were the most reliable (Area Under the Curve >0.7). ... This highlighted not only issues of data prevalence, but also how ecological models can be used to test the reliability of classification schemes. Care should be taken when mapping predicted habitat occurrence with broad habitat models. It should not be assumed that all habitats within the type will be defined spatially, as this may result in the distribution of distinctive and unique habitats such as filterfeeders being underestimated or not identified at all. More data is needed to improve prediction of these habitats. Despite the limitations identified, the results provide direction for future field sampling to ensure appropriate variables are sampled and classification schemes are carefully designed to improve descriptions of habitat distributions. Reliable habitat models that make ecological sense will assist future assessments of biodiversity within habitats as well as provide improved data on the probability of habitat occurrence. This data and the methods developed will be a valuable resource for reserve selection models that prioritise sites for management and planning of marine protected areas.

Thesis (M.S.)--West Virginia University, 2009. / Title from document title page. Document formatted into pages; contains xvii, 195 p. : ill. (some col.), col. map. Includes abstract. Includes bibliographical references (p. 58-90).

京都大学 / 新制・課程博士 / 博士(工学) / 甲第23488号 / 工博第4900号 / 新制||工||1766(附属図書館) / 京都大学大学院工学研究科都市社会工学専攻 / (主査)教授 角 哲也, 准教授 竹門 康弘, 准教授 Kantoush Sameh / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Dramatic declines in many species of demersal fishes off the West Coast have resulted in the designation of nine commercially important species as being overfished. While the causes of those declines are not clearly understood, the fact remains that a paucity of life history and abundance data exists for many demersal species, also known as groundfish. Due to this uncertainty, only 21 of the 82 species of groundfish managed under the Groundfish Fishery Management Plan of the Pacific Fishery Management Council (PFMC) have been fully assessed. One challenge in designing a systematic survey of groundfish resources is that many species associate with heterogeneous substrate of varying relief. In many areas, the rugosity of the substrata precludes sampling by conventional techniques (e.g. bottom trawl gear). This has stimulated research that characterizes fish-habitat associations for use in design of new survey methodology. Using a combination of remote sensing, in situ observations, and spatial analytical techniques, four benthic habitat classes were mapped for a large rocky bank off the central Oregon coast known as Heceta Bank. Observational data from human-occupied submersible and remotely operated vehicle dives in the late 1980s, 2000 and 2001 were used to establish habitat classes with specific substrate characteristics that have been statistically shown to correlate with demersal fish distributions. The observational habitat data was then extrapolated over the extent of a multibeam sonar survey conducted in 1998 using quantitative parameters derived from high-resolution bathymetric and backscatter imagery of the seafloor. The resultant map predicts the locations of four habitat classes: Ridge-Gully, High-Relief Rock (boulders, cobbles), Unconsolidated Sediment 1 (muds), and Unconsolidated Sediment 2 (sands). The main utility of the habitat map developed as part of the current study is that it provides a context for analyses of a variety of spatial data. For instance, habitat data provides one additional spatial component besides depth and latitude that can be used to stratify catch per unit effort data from surveys and commercial logbooks. Also, essential fish habitat for many demersal species can now be identified in more detail. Finally, habitat data like those presented here can aid in the design of marine reserves and protected areas by providing a context for spatial analyses of data of ecological importance. / Graduation date: 2003

Thesis (M.S.)--University of Tennessee, Knoxville, 2010. / Title from title page screen (viewed on July 20, 2010). Thesis advisor: Paul Ayers. Vita. Includes bibliographical references.

The ecological position of micro-algae at the base of the aquatic food web makes them critical components of aquatic ecosystems. Their short generation time also makes them useful biological indicators because they respond quickly to changes in environmental condition, enabling timely identification and assessment of water quality changes. The inclusion of micro-algae as indicators in water resource regulation and management in South Africa has started recently, their more extensive use in biomonitoring and ecotoxicology programmes for water resource management would contribute to the South African policy if water resource protection. The standard algal growth inhibition assay with the species Pseudokirchneriella subcapitata is currently used for monitoring toxicity of in-stream and industrial wastewater discharges to freshwater micro-algae. The relevance of the data generated by standard toxicity bioassays has been questioned, since micro-algae in particular are extremely variable in their sensitivity to a range of contaminants and these standard species used may not occur in the local aquatic environment. As a result, international regulatory agencies, have recommended algal growth inhibition tests be changed from a single standard species to tests with a number of species. One recommendation, in addition to the use of standard toxicity tests, is the use of species isolated from the local environment which may be more relevant for assessing site specific impacts. This study investigated the value and application of locally isolated South African freshwater micro-algae in toxicity tests for water resource management and was carried out in three phases. The first phase involved isolating micro-algae from South African aquatic resources. Micro-algae suitable for toxicity testing were identified and selected using as set of criteria. Three (Scenedesmus bicaudatus, Chlorella sorokiniana and Chlorella vulgaris) out of eight successfully isolated species satisfied the prescribed selection criteria and these were selected as potential toxicity test species. The second phase focused on refining and adapting the existing algal toxicity test protocol (the algal growth inhibition assay) for use on the locally isolated algal species. The refinement of the test protocol was achieved by exposing the locally isolated species to reference toxicants in order to assess and compare their growth and sensitivity to the toxicants under the prescribed toxicity test conditions with that of the standard toxicity test species (Pseudokirchneriella subcapitata) and a commercial laboratory species (Chlorella protothecoides). During this phase, one of the three local species (Scenedesmus bicaudatus) was eliminated as a potential toxicity test species due to inconsistent growth. The third phase of the study involved assessing the sensitivity of the two remaining species (C. vulgaris and C. sorokiniana) to a range of toxicants (reference toxicants, salts, effluents and a herbicide) and comparing it to that of the standard toxicity test species P. subcapitata and C. protothecoides. The toxicants were selected based on their relative importance in the South African context, as well as the practicality of using these local micro-algae to routinely determine the impact of these toxicants on local aquatic resources. The growth of the four micro-algae was stimulated by the selected effluents. The standard toxicity test species P. subcapitata was ranked the most sensitive and of the four species to two reference toxicants and two inorganic salts. Chlorella sorokiniana was ranked the most sensitive of the three Chlorella species to two reference toxicants and two inorganic salts. The herbicide stimulated the growth of C. vulgaris while inhibiting the growth of the other species. Pseudokirchneriela subcapitata and C. sorokiniana showed high intra-specific variability in growth, which made it difficult to determine the effective concentrations of the herbicide and therefore compare the sensitivity of the species. This varied response of micro-algal species to toxicants may result in the biodiversity shifts in aquatic ecosystems, and also supports the recommendation of using a battery of different species to support more informed decisions in water resource management.

Le paysage des rivières en tresses est constitué d’une riche mosaïque d’habitats diversifiés, déterminée par un ensemble de facteurs biophysiques qui interagissent à différentes échelles spatiales et temporelles.A partir d’une sélection de 53 tronçons en tresses, nous avons réalisé une analyse comparative à l’échelle régionale du bassin du Rhône et en fonction de plusieurs échelles temporelles, en mobilisant les techniques de télédétection.Premièrement, nous avons étudié la variabilité de la structure des habitats aquatiques et du patron des chenaux. Nous montrons que le patron de tressage et des habitats aquatiques n’est pas uniquement lié au débit, mais aussi aux conditions locales liées aux apports sédimentaires et à la présence de la nappe phréatique.Deuxièmement, nous avons abordé une approche diachronique afin de comprendre l’évolution à moyen terme du paysage fluvial de ces tronçons, depuis la moitié du siècle dernier. Les résultats montrent que toutes les tresses du bassin rhodanien ne sont pas déliquescentes et que certains tronçons sont encore très actifs. Cela dépend d’un ensemble de facteurs : la position géographique du tronçon, son évolution à court terme liée aux épisodes de crues et l’histoire des conditions anthropiques environnantes.Enfin nous avons analysé les trajectoires évolutives suivies par un sous-ensemble de 12 sites, analysés à une échelle temporelle plus fine (5 observations par site sur 50 ans). Nous observons que les tronçons suivent des trajectoires différentes, en fonction des conditions hydrologiques observables à un moment donnée (ex. crues), de la position géographique du tronçon et du contexte anthropique. De plus, certaines conditions locales (topographie et humidité relative) semblent aussi nécessaire à la compréhension du patron biogéomorphologique des tronçons étudiés.A partir de ces résultats des éléments de perspectives pour une gestion intégrée des rivières en tresses du district rhodanien sont proposés. / The landscape of the braided rivers is characterised by a rich and diversified mosaic of habitats. The variability of the braided riverscape depends upon the combination of bio-physical factors, which interact at the different spatial and temporal scales.We did a comparative analysis at the regional scale of 53 braided reaches selected in the Rhône basin district. We used a remote sensing-based approach.At first, we analysed the aquatic habitat and the river channel pattern. We showed that the braiding and aquatic habitat patterns do not depend only on the flow regime but also on some local scale conditions, such us the sediment regime and the presence of the “near-floor” groundwater.Secondly, we moved on the overall riverscape corridor, and we applied a diachronic analysis comparing the present state of reaches with their state at the mid of the last century. The results show that not all studied braided reaches are narrower today compared to the 1950s and that some reaches are even wider. It is linked to a combination of several factors, such as the geographical position of a reach in its catchment and the short-term evolution ruled by recent large floods, as well as the history of the catchment linked to human settlements.Then we focused on the evolutionary trajectories followed by a sub-set of 12 braided reaches through time, and we increased the temporal resolution, for a total of five dates per reach. The results show that reaches follow different trajectories depending on: the hydrological conditions at a given period (e.g. floods), the geographical position of a reach at the regional scale and the anthropic context. Additionally, it seems that also local conditions (in terms of topography, sedimentation, and soil moisture), play an important role in determining the biogeomorphological pattern of the studied reaches.From these results, we discussed some perspectives for the braided river management in the Rhône basin district.