Richard D. Hedger

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Changes in snow and ice conditions are some of the most distinctive impacts of global warming in cold temperate and Arctic regions, altering the environment during a critical period for survival for most animals. Laboratories studies have suggested that reduced ice cover may reduce the survival of stream dwelling fishes in Northern environments. This,(More)
The short-term relationships between the spatial distributions of phytoplankton and the environmental conditions of Esthwaite Water, a small eutrophic lake in the English Lake District, UK, were examined using a hydrodynamic model. Spatial distributions of phytoplankton were simulated on two occasions the first, when the population was dominated by(More)
Patterns of summertime movement and habitat use of yellow-stage American eels Anguilla rostrata within York River and estuary and Gaspé Bay (Gaspesia, Québec, Canada) were examined using acoustic telemetry. Fifty fish were tagged with acoustic transmitters and released, either in the river or in the upper estuary, and their patterns of movement and habitat(More)
Factors influencing the migration and swimming depth of Atlantic salmon kelts Salmo salar L. within the York Estuary and Gaspé Bay (Québec, Canada), and in the Gulf of St. Lawrence between Gaspé Bay and the Strait of Belle Isle (Newfoundland, Canada) were studied using acoustic telemetry. In 2006 and 2007, a total of 49 kelts were tagged with acoustic(More)
Rapid dewatering in rivers as a consequence of hydropower operations may cause stranding of juvenile fish and have a negative impact on fish populations. We implemented stranding into an Atlantic salmon population model in order to evaluate long-term effects on the population in the Dale River, Western Norway. Furthermore, we assessed the sensitivity of the(More)
We studied downstream migration of 256 radio-tagged Atlantic salmon smolts passing a low-head power station where technical facilities have been improved to allow safe migration via several bypass routes. Extra mortality was 7 and 17% (two years) in the power station reservoir, and a minimum of 10 and 13% at the power station compared to in a control(More)
Hydropeaking induces flow alterations in rivers caused by hydropower plants. Water is released or held back depending on the power demand and hence changes the flow regime of rivers. To assess the ecological impact of such management strategies ecological models can be used. Models for ecological systems can be based on various approaches and as such focus(More)