Dissertations & Theses

Permanent URI for this collection

Recent Submissions

Now showing 1 - 5 of 6
  • Publication
    Atlantic Salmon Spawning Migrations in the Penobscot River, Maine: Fishways, Flows and High Temperatures
    (1995) Shepard, S L
    Restoration of Atlantic salmon, Salmo salar, to the Penobscot River in Maine has met with limited success to date. Research in freshwater has emphasized migration problems created by dams. Fish passage research was initiated jointly by the Maine Atlantic Sea Run Salmon Commission and the Bangor Hydro-Electric Company in 1987. This research was later broadened to examine environmental issues of flow and temperature. From 188 through 1992, radio transmitters were placed in the stomachs of 108 returning adult Atlantic salmon which were then released at several locations in the lower Penobscot River. Radio-tagged Atlantic salmon were monitored with receivers and data loggers at six hydroelectric dams and by mobile tracking from airplanes, trucks, and boats. Radio-tagged Atlantic salmon made no net upstream progress for weeks at a time during the summer. When directed upstream movements were initiated, salmon passed through multiple fishways and often made net progress of 20 to 40 km in five to ten days. Atlantic salmon passed through fishways below 23ºC, but higher temperatures were associated with fewer radio-tagged Atlantic salmon passages and reduced captures at the Veazie Dam fishway trap. Above a threshold of approximately 23ºC, increasing temperatures caused Atlantic salmon to cease movement and seek refuge in stream mouths where they usually remained until high temperatures abated. Daily average temperatures of 26ºC to 27ºC were associated with salmon mortalities. When radio-tagged Atlantic salmon migrated upstream to the Piscataquis and Mattawamkeag rivers, migrations often ceased again, apparently due to low flows in these unregulated tributaries, Main stem and East Branch flows were artificially high due to releases of stored water and there was no indication that migrations were impeded by the lowest flows observed in those areas. In contrast, high main stem flows may have inhibited upstream passage at lower Penobscot River dam as a result of attraction to spillway flows which compete with turbine flows where fishway entrances were typically located. Low velocity areas such as impoundments were not suitable holding habitat and radio-tagged Atlantic salmon moved rapidly through these areas. Radio-tagged Atlantic salmon were generally found in areas of moderate to high velocity and moderate to shallow depth.
  • Publication
    Factors Affecting Spawning Site Selection and Hatching in Anadromous Rainbow Smelt (Osmerus mordax, Mitchill)
    (1974) Hulbert, P J
    Physical factors which might influence spawning site selection and hatching success in anadromous rainbow smelt (Osmerus mordax) were investigated. Water depth, water velocity, distance upstream, stream temperature, tide height, and estimated spawning time accounted for 33% of the variation in egg deposition in one stream and 14% in a second stream. Multiple linear regression of egg deposition on physical factors showed water velocity, distance upstream, temperature, and estimated available spawning time had regression coefficients significantly different from zero. Hatching success in laboratory experiments ranged from 15 to 34% in 1972 and 17 to 61% in 1973. Analysis of variance in percentage hatch indicated eggs incubated on sand had significantly lower hatching success than eggs incubated on two sizes of gravel or on an artificial spawning substrate. Differences in effective circulation within incubation jars apparently caused variations in time to hatching.
  • Publication
    Re-establishment of connectivity for fish populations in regulated rivers
    (2005-01-01) Calles, O
    The hydropower industry has altered connectivity in many rivers during the last century. Many fish species depend on both an intact longitudinal connectivity to be able to migrate between spawning, feeding, and winter habitats, and vertical connectivity for development and survival of incubating embryos and larvae in the gravel. The objective of this thesis was to examine problems and remedial measures associated with disrupted longitudinal and vertical connectivity in regulated rivers. The issue of longitudinal connectivity was studied in the River Eman by evaluating the efficiency of two nature-like fishways for anadromous brown trout. Telemetry studies showed that the combined efficiency for the two fishways in 2001-2004 was 60.5%. The passage efficiencies of both fishways were high for trout (89-100%), but also for other species such as chub, perch, tench, burbot, and roach (74%). The attraction efficiencies were largely dependent on power plant operation, and generally high for the fishway situated next to the tail-race and low for the fishway situated inside the former channel. More than half of the trout spawners were also observed using the fishways for downstream passage. The densities of brown trout yearlings upstream of the fishways were higher after the fishways were built than during pre-fishway years. Smolts produced upstream of the fishways were observed migrating downstream in 2003-2005. The mean percentage of smolts that passed both power plants was 51%, with losses being attributed to predation (15%), turbine-induced mortality (16%), and other reasons (18%). Turbine-induced mortality was higher (40%) at the power plant with four small Francis runners than at the power plant with one large Kaplan runner (12%). The issue of vertical connectivity was studied in three rivers in Varmland, one unregulated, and two regulated, one of which had no minimum flow requirements. In the unregulated river, temporal patterns in hyporheic water chemistry correlated to variation in surface water chemistry and discharge as expected. In the regulated rivers, the hyporheic water chemistry showed little correlation to discharge or surface water chemistry. The intra-gravel water chemistry conditions for brown trout eggs were more favourable in the unregulated river, characterised by high oxygen levels, than in the two regulated rivers. The regulated river with no minimum flow requirements had critically low oxygen levels at the end of the incubation period.
  • Publication
    Restoring Salmonid Stocks in Boreal Rivers
    (2001-01-01) Laine, A
    In this thesis, I examine two important aspects surrounding salmonid reproductive ecology, namely: (i) the problems with passing obstructions during migratory spawning runs and (ii) how the early life stages in boreal streams are influenced by increased levels of fine-grained particulate matter from drained peatlands. These aspects are not only critical to salmonid reproductive success but have grave implications regarding environmental quality and species conservation. Spawning runs can be re-established by constructing fishways at obstructions but the efficiency of fishways depends on several factors. The passage of multi-sea-winter salmon was enhanced in the Isohaara fishway by increasing its water flow and by creating a small waterfall at the entrance. The fishway, which consists of vertical slot and Denil sections, proved to be unsuitable for most freshwater fish, whitefish, and river lamprey, whereas salmonids, once they had entered, successfully negotiated the fishway. In fishway design, the migratory behavior and the demands of the species of interest should be considered. For salmonids, priority should be given to the attractiveness of the fish entrance. When there is a migration corridor, the availability and the quality of the spawning and rearing habitats has a major effect on the success of restoration projects. In the humid rivers studied, the survival of incubated brown trout eggs was lower in riffles susceptible to increased levels of fine-grained particulate matter from drained peatlands. Additionally, an increase in the Fe content of high molecular weight dissolved organic matter followed by its precipitation and sedimentation was proposed to be involved. Correspondingly, the recapture rates of stocked and yearling salmon were lower in the affected riffles, individual salmon being smaller and thinner and having less food in their stomachs than reference salmon. Based on these results, it seems probable that peatland drainage, by influencing the incubation success of salmonid embryos and the foraging, growth, and survival of juveniles, eventually affects the number and quality of smolts produced. In future, such water pollution control measures should be implemented that would enhance the success of natural spawning and help ensure environmental quality.
  • Publication
    Analysis of Slot Orifice Fishway
    (1970) Dass, P
    The object of this study was to develop design criteria for a slot orifice fishway. Sizing and spacing of slot orifices inside the fishway can be designed to create flow conditions satisfactory for fish passage. The slot orifice fishway will function well in a wide range of discharges and should not have any serious silting problems. Values of drag coefficients for the slot orifice constrictions were evaluated by model studies for a range of slot openings varying form 0.6 to 0.85 of fishway width and culvert slope varying from horizontal to five percent. Three longitudinal spacings, 4, 5, and 6 times the fishway width, were considered for the slot orifices in the fishway. The effect of tailwater on the flow conditions at the fishway entrance was studied. The backwater relation of the slot orifice also was developed in the above range. Nondimensional curves are given for the values of the drag coefficients of the slot orifice constrictions and also for the backwater relations for the slot orifices. An equation, based on momentum principle, is developed which enables the designer to find the rate of flow through the fishway. Necessary criteria regarding suitability of flow for fish passage are also developed.