Page 30 - Green knowledge 2024

Photo: Roger Roseth
Fish thrive despite road work
Fish monitoring in surveyed streams during the construction phase of several major road
construction projects shows good production of both sea trout and salmon.
Researchers at NIBIO have been monitoring sea
trout and salmon in waterways affected by major
infrastructure projects for several years, including
along the E18 route Langangen-Rugtvedt. The goal
has been to see how fish populations and bot-
tom-dwelling organisms are affected by particle and
nitrogen emissions during construction activities.
“The fish have managed surprisingly well, even
though the water quality has been poor at times. In
some places, the fish population has even increased,”
says Roger Roseth, senior researcher at NIBIO.
One possible explanation is that turbid water reduces
predation, as fish become less visible to predators.
Low visibility means fish defend smaller territories,
allowing greater density. When water is unclear, fish
move more freely without fear of being caught.
Other species, such as the vulnerable freshwater
mussel, also seem to tolerate the pressure better than
expected. In large waterways such as the Åbyelva and
Sogna, where particle and nitrogen concentrations
are diluted, road construction has had few visible
effects on the freshwater mussel. Some bot-
tom-dwelling organisms, such as net-building cad-
disflies, may, however, face greater challenges, as
particles from construction activities destroy their
food webs.
When roads are completed, studies will assess long-
term population effects. Roseth wants to see if preda-
tion increases when water clears and whether this
reduces fish density. Future concerns when the new
roads are in operation include runoff of metals, sul-
phate, microplastics, and road salt affecting water
quality and wildlife.
Purpose: Monitoring water environment in connection with road construction.
Collaboration: Faun and Naturplan
Funding: Statens vegvesen, Bane NOR, and Nye Veier/Eiffage
Contact: Senior Research Scientist Roger Roseth, Division of Environment and Natural Resources.
Email: roger.roseth@nibio.no | Phone:
+
47 926 16 344
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