Summer. Hot water in Råån and low water level.
If it then rains and at the same time there are discharges of organic material in the stormwater pipes, the result can be devastating for the fish in the river.
The oxygen content drops and the fish suffocate to death.
Dead fish in the water surface
– It is really very boring, says Martin Sommar, expert in Rååns Fiskevårdsområde, who has seen this happen repeatedly – dead fish floating in the water surface. Or has sunk to the bottom. It can be about hundreds.
– Trout are most sensitive when the oxygen content decreases due to emissions, they are affected first. But roaches, perch and pike are also affected.
NSVA, Northwestern Skåne’s water and sewage, has for several summers tried to find the cause of the fishing deaths in Råån. It has been concluded that it is due to the release of organic material into the stormwater pipes.
But now the hunt for emissions is escalating. A special sampler with 24 different bottles is now in a stormwater well and constantly takes samples.
– We hope to be able to find something this time, says Lotta Wallin.
Like finding a needle in a haystack
But no one knows where the organic material comes from. It is not a constant emission but happens from time to time.
– Sometimes there are high levels in the stormwater pipes, sometimes nothing at all. It’s like looking for a needle in a haystack, says Lotta Wallin, group manager at NSVA’s environmental department.
The emissions may last for a few minutes, when it is discovered the source is gone. The only thing that is clear is that according to Lotta Wallin, it is located somewhere in the Ättekulla industrial area, where several companies handle organic material.
– We have examined all the pipes but in any case find no leak, says Lotta Wallin.
This is how we reported last summer after dead fish were found in the river again: