What does limestone have to do with fish in Vemdalen? A lot! After years of acidified watercourses, liming was carried out and the trout, a species that was dying out, have now found their way back.
Every year, hundreds of thousands of tons of limestone are spread across Swedish lakes, watercourses and wetlands using helicopters, boats and dosers with the aim of counteracting acidification.
Reduction in fish stocks
Watercourses in Vemdalen have long been battling against acidification. Sulphur emissions in Europe in the 1970s damaged the water, leading to a decrease in both the pH value and trout population. After extensive work was carried out at the beginning of the 1990s the fish found their way back, but a few years later, liming operations were ceased in spite of their success.
– Because of the decrease in sulphur emissions and increase in the trout population, liming was no longer considered necessary, says Leif Rodhe, who is in charge of liming operations at Berg Municipality.
Annual liming operations
Regular liming improves the quality of water and provides fish with a better habitat, which is why Berg Municipality has decided to start liming Oxsjöån’s drainage basins again.
– Since last autumn we have spread approximately 100 tons of limestone in Oxsjöån and the surrounding wetlands and our goal is to lime every year. This is our chance to preserve trout, Leif Rodhe explains and goes on to say:
– If the trout disappear it leads to a number of other problems, including a reduction in whitefish stocks. We have an extremely complicated ecosystem to take into account.
Was the operation successful?
– Yes, definitely. Last autumn we carried out an electrofishing survey to see how trout stocks had changed and we were pleased to see a huge increase in the number of yearlings. The trout have responded extremely well to liming.
Lake liming, 5 fast facts
• Lake liming prevents acidification. The recommended course of action is to carry out the procedure on a regular basis in order to retain a level pH value. How often the procedure is carried out depends on the turnover time of the water in question
• Lake liming is carried out by boat, helicopter or dosers that portion out the limestone. To simplify helicopter liming, sacks of limestone are driven out to accessible areas in the forest.
• Natural, ground limestone is used for lake liming, but the stone is more finely ground for application via dosers. When liming wetlands, more coarsely ground limestone is used and it is also moistened in order to prevent the dust from spreading to surrounding vegetation.
• All lake liming procedures must follow a clear plan that includes a pH goal. In Vemdalen the liming plan was to entice back the trout and reach a pH value of 6.0.
• In order to check that lake liming is beneficial, the water’s pH value is measured several times per year.
The liming in Vemdalen was so successful that the municipality has now set a goal of liming every year.
Photo: Karl Vertergård/Destination Vemdalen