The fish are marked on the underside to prevent them from swallowing the chip. The chip is usually removed when the fish are gutted. This means that nobody needs to worry that their movement data will suddenly appear on Walter Reckendorfer's computer. In addition, the fishermen are warned about the transmitter by their fishing associations and asked to return it. This is another way of collecting data on the fish. But the intention is different.
Receiver stations are installed along the fish migration aid, which are addressed by the fish's transmitters. In this way, we know the movement behavior of the fish and can find out the different preferences of the species. How long does a fish stay in the fish migration aid? How often does it use the fish migration aids - and the old question of all power plant operators: how many fish use the navigation locks on the Danube to migrate, and how many whistle on the strenuous journey over the fish ladder? What is already quite normal in supermarkets - customers log their cell phones into the free WLAN and the company tracks their movement profile - is now also happening in the fish migration aids.
