Nearly 1,000 meters above sea level is the lake that can be seen from the famous mountain road above Bisjen.
In recent years, many disturbing discoveries have been made in Gjende. Fishermen report that the salmon is very thin and that the largest salmon are almost out.
The life of insects has also changed.
In all years, large swarms of so-called reindeer flies are found in August in Gjendeosen, where there is an outlet for water. But in recent years, swarms of flies have disappeared.
Nobody really knows why this happens.
2.5 degrees warmer
In a new report, the Norwegian Institute for Natural Research (NINA) has reviewed all available fish data from Gjende up to the early 1900s. This applies to both observations made by hunters and scientific research.
Based on the report, the Norwegian Environment Agency concluded that climate change is most likely the cause of the observed changes.
– In recent years, there have been reports of concern about Gjende trout. The catch was significantly reduced, and the fish was partially meager. This was especially the case after 2018. Currently Observations about the negative development of trout in Gjende are confirmed.
Director Elaine Hambor at the Norwegian Environment Agency writes in a summary received by NRK.
The water temperature in Jendi rose by 2.5 degrees in August from 1995 to 2020. The Norwegian Environment Agency writes that increased melting of the Gothenheim glaciers has led to more glacial mud and poor visibility in the water. Lack of vision will have a negative effect on fishing for food.
Watch the NRK Nature Documentary about Gjende and gjendeflua from 2016.
Strong retreat to fly back
At the same time, there has been a sharp decline in the returning fly, an important fish industry.
Gjendeflua is a species in the knob family. It is about 3-4 mm long and it was a familiar sight through these waters. The larvae attach to the rocks in the water and filter nutrients from the water masses.
Scientist NINA’s Stein Ivar Johnsen works on a separate report on the reindeer fly and compared conditions in 2012 and 2021.
– When we were there in 2021, we hardly saw a fly at all inside, he says.
Johnson says it’s hard to say for sure what caused the decline. But he thinks what stands out are the very hot summers.
– In 2018 and 2019 in particular, it was very hot with a lot of glaciers melting. A lot of icy mud appeared in Gendi herself, causing the depth of view to decrease. This, in turn, leads to reduced production of phytoplankton and zooplankton, he says.
NINA researchers will also investigate whether the construction of a new pier at Gjendeosen may be a contributing factor.
can come back quickly
But it doesn’t look completely black. Scientist Stein Ivar Johnsen has positive news to report.
– The positive is that there is still a fly back in the system. So it did not disappear. The returning fly has a very large ability to reproduce. If there are better seasons, it can come back quickly, he says.
Gjende is part of the Norwegian Environment Agency’s monitoring program for the Great Lakes called ØKOSTOR, and therefore will be pursued in the coming years.
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