A fish count in the Isar showed that the stock of brown trout and Koppen has fallen by half.
Another species of fish, meanwhile, appears to be recovering.
Lenggries/Wallgau
– where are the brown trout?
An examination of the population in autumn between Krün and Wallgau found that there had been a 40 percent decline.
The State Office for the Environment (LfU) had carried out a fish count and water analysis on a section of 600 meters.
Fish stocks in the Isar are getting worse and worse
It was determined that - according to a spokesman for the LfU - the fish fauna on the Upper Isar was "in good ecological condition".
However, the number of brown trout has decreased by almost 40 percent, and that of the Koppen by almost 50 percent.
The decline can also be felt in the further course of the Isar.
"The fish stock is getting worse and worse," says Michael March, chairman of the fishing association Lenggries.
“We are investing a lot of money so that we can occupy the Isar over the long term.
But that is always a huge effort.”
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Minnows feel at home in the Isar.
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As a main reason for the decline in many fish species, but also crabs, March sees the increase in the otter: "A huge problem." The damage caused by the otter goes into the thousands.
Goosanders and cormorants are also increasing.
In addition to the predators, Hans Schanderl from the Garmisch-Partenkirchen district fishing association has an explanation for the decline in the bullheads: "Wherever the water on the Isar runs dry, the bullheads have a hard time." In contrast to its conspecifics, the fish does not have a swim bladder and can therefore only do short ones overcome distances.
"They are tough, but they are particularly endangered when the water is receding or seeping away." According to Florian Herzinger from the district fishing association in Bad Tölz, the brown trout also have to contend with a parasite that is reducing stocks.
Grayling in the Isar is recovering
The fish stocks in the Isar in the Lenggries and Bad Tölz areas are checked again and again.
The counting is done with electric aggregates.
Herzinger can confirm the decline in Koppen and brown trout.
The grayling, on the other hand, is fine.
“We have been protecting them for some time on the part of the fisheries.
As a result, it recovers naturally and is also better able to withstand predators.” Because these natural enemies are increasing.
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Dead Koppe, died when the Isar was dry.
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That is why the fisheries are increasingly urging them to be able to build shelters in the form of deadwood or stones in the Isar.
This is possible on the part of the water management office.
But there is a conflict of interest with the commercial users of the Isar, i.e. the boaters.
"You want to go down a wild river, but you don't want to bring any structures into it.
That's a shame.” You have to find a good balance.
The shelters are designed to protect the fish.
"The young fish can hide there from birds or other fish," explains Herzinger.
There are a few such protective surfaces, but more are needed.
Fish spawn near the Gaißach soccer field
The Isar is under close observation at the level of the Gaißach soccer field.
Because that's where the fish spawn, all of which are gravel spawners.
Even if you compensate with the introduction of fish: "The best thing is if the fish reproduce for the most part themselves." The huchen and grayling are ready.
Other fish species must be introduced every year.
"But we like to do it, even if it's expensive." Because fishing is also committed to nature conservation.
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Brown trout have become fewer.
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You can find more current news from the region around Bad Tölz at Merkur.de/Bad Tölz.
