Juvenile coho, steelhead, and cutthroat trout commonly spend from one to three or more years in coastal streams before migrating to the sea. Much of this time is spent in streams during the winter, making a study of these fishes' winter habitat requirements, distribution, behavior, and the possible influences of stream habitat alteration on them a useful undertaking. Some physical characteristics of areas selected by juvenile coho and steelhead were observed by snorkeling in a small west coast of Vancouver Island stream between September 1972 and April 1973. Observations revealed that with lowering water temperatures from 9°C to 2°C coho and older steelhead tended to move into deeper water while most steelhead fry remained in shallow, marginal sections of the stream. As water temperatures dropped in the winter, juvenile fish fed less and moved closer to areas offering low water velocities and cover. Steelhead fry were most often found under rubble while coho and older steelhead were most often found within upturned roots and under logs. Results from fish traps located on the lower ends of two small tributary streams indicated that juvenile coho, steelhead and cutthroat trout moved upstream into these tributaries in the late fall. Overwinter survival of coho in one tributary was 3-6 times as great as the estimated survival of coho in the main stream. Together the two tributaries contributed between 15 and 25 per cent to the total coho smolt production of the larger system. A series of experiments comparing coho and cutthroat preference for alternative habitat types in sidepool areas as may occur before and after stream disturbance were carried out during the winter. Both coho and cutthroat demonstrated a strong preference for bay areas offering overhanging bank cover as opposed to bays without cover, and for bays offering clean rubble substrate as opposed to silted rubble substrate. The impacts of timber harvesting on overwintering fish as suggested by the results from the underwater observations, winter movements, and the sidepool experiments are discussed and management recommendations are made. / Forestry, Faculty of / Graduate

As landscapes become increasingly urbanized, there is an associated increase in impervious cover. Impervious surfaces, such as roads, rooftops, and parking lots contribute to the physical, hydrological, chemical, and biological alteration of stream systems. Biotic assemblages consistently degrade with increased watershed impervious cover; however, at low levels of impervious cover, these assemblages exhibit wide variability in biotic integrity. This study investigated which reach- and watershed-scale factors explained biotic condition (i.e., richness, flow traits, thermal traits, and tolerance for macroinvertebrates and fishes) at similar levels of low imperviousness. The primary objective was to identify factors that confer resistance for biota, such that they retain high biotic integrity at low levels of impervious cover, and, conversely, to determine which factors make biota more vulnerable to urban disturbance, such that they have low biotic integrity despite low levels of impervious cover. Forty sites were selected across Massachusetts within two narrow bands of impervious cover: 1–4% (n = 20) and 7–10% (n = 20). Models with reach-scale variables (reflecting habitat heterogeneity, flow, temperature, or water quality) or watershed-scale variables (representing natural characteristics, land use, flow alterations, and other measures of urbanization or impervious) explained additional variance compared to models with impervious cover alone. Reach-scale factors tended to explain more variance than watershed-scale factors for all biotic responses except fluvial fishes, with overall more variance explained for fish than macroinvertebrate assemblages. At the reach scale, colder water temperatures, higher dissolved oxygen, and more large wood were related to higher proportions of fluvial, coldwater, and intolerant fishes. For macroinvertebrates, warmer water temperature, smaller sediment size, and higher nitrate were related to higher macroinvertebrate richness and tolerance. At the watershed scale, air temperature emerged as an important predictor for both taxonomic groups and across response metrics; air temperature was highly correlated with high-elevation watersheds. Other important watershed-scale predictors were open water and dams, flow alteration, and other urban measures such as housing density, impervious in a 120-m buffer, and road crossings. Restoration should focus on strategies to reduce impacts that would degrade in-stream conditions that allow for higher biotic integrity, such as habitat heterogeneity, more large wood, and colder water temperatures. Similarly, watersheds should be prioritized for protection with those characteristics potentially more resistant to urban disturbance, such as high-elevation regions that retained high biotic integrity despite higher dam density, more road crossings, and more flow alteration.

A research report submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in partial fulfillment of the requirements for the degree of Master of Science in Engineering Johannesburg, 2018 / The main objective of this report is to assess the effect of different topographic (elevation) data sources on river habitat modelling in low flow conditions. In the study, digital terrain models which consists of various datasets were assessed using 2-D hydraulic software models. The representation of the terrain was sourced from the following: airborne laser scanning, total station survey, a smartphone device and a handheld GPS device. From the results, which consisted of 4 simulations (discharges of 1.5 m3/s, 1 m3/s, 0.5 m3/s, and a field measurement of 0.3 m3/s) for each topographic dataset, the water level and velocity were derived and a comparison was made against the most accurate data set (total station survey). The comparisons included how each model was able to describe a habitat in terms of defined biotopes. This research proves that a total station survey is still the most accurate, however with the advancement in GPS technology a handheld GPS device has proven to be adequate for a desktop or intermediate study. In addition, a smartphone’s GPS tends to be more adequate for large surveys and inefficient for habitat modelling. / MT 2018

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We investigated variations in resource availability (nitrate and labile organic carbon, LOC) as determinants of denitrification in sediments of streams in the southern Appalachian Mountains, USA. Stream water and sediments were sampled seasonally in two streams of contrasting nitrate availability, Noland Creek (high NO₃-N) and Walker Branch (low NO3-N). Eight additional streams with varying nitrate levels were sampled once during summer. Stream sediments were incubated at ambient stream temperatures, and nitrous oxide accumulation was quantified following acetylene inhibition of nitrous oxide reduction. Denitrification potential was greater in Noland Creek than Walker Branch and was generally greater in sediments from the higher-nitrate streams. In autumn and spring, nitrate and LOC amendments indicated that denitrification potential in Walker Branch sediments was nitrate limited, with temperature having no effect on rates. Denitrification potential in Noland Creek sediments was not limited by nitrate, but temperature had a significant effect. When Noland Creek seasonal data were corrected to a common temperature, no seasonal differences in denitrification potential were detected. Nitrate-N in the 10 surveyed streams ranged from 10 to 549 mg/L, with the highest NO₃-N levels and denitrification rates generally occurring in the higher elevation streams in the GSMNP. We found that nitrate availability, more than LOC availability, controls potential denitrification in these streams. / Master of Science

Thesis (M. Phil.)--University of Hong Kong, 1974. / Typewritten.

Thesis (M.S.)--Oregon State University, 1989. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.

Thesis (M.S.)--Oregon State University, 2009. / Printout. Includes bibliographical references. Also available on the World Wide Web.