Fisherman friend of the Danube

Dr. Gábor Guti is one of the leading research workers of the Hungarian Danube Research Station of the Hungarian Academy of Sciences, and he is the member of several Hungarian and international scientific societies as well. He has been carrying out researches for nearly two decades on river-fish – mostly in the Hungarian section of the river Danube – and he gives lectures in some institutes of higher education.

During his childhood he used to fish regularly in the river Danube downstream from Budapest, near Százhalombatta. "In those days we could catch many fish. Although the members of my family liked fish meals, sometimes my parents told me not to carry home any fish when I went fishing. Nowadays I go fishing with my son, and I realized that in the same places, with the same methods we can not achieve the same catch, I fished 30 years before,” said Mr. Guti.

In the last decades several factors determined the changes of fish populations. According to Mr. Guti, one of the most important factors is the deepening river bed of the river Danube that has negative effects on the natural habitats of fish. The decreasing number of fish in the river Danube can be also demonstrated by the fishing data of the last decades. But if we compare the current fishing data to the sturgeon catches of the Middle Ages, the change will be more conspicuous.

He mentioned the decreased number of fish in the river Tisza as an example for the negative effects of river regulation works. The flood-plains of this river used to provide huge spawning grounds and proper habitats for the fish, this way enabling abundant supplements for the fish populations. But due to the river regulation works, the river Tisza has lost more than 90% of its original flood-plains. According to the former data of the National Fishing Inspectorship (OHF), the number of fish has decreased by 99% in the river Tisza. This change was overwhelming for the traditional fishing activities around the river.

The last sturgeon was caught in 1987 in Hungary

The sturgeon was one of the most important fish species in the Middle Ages along the river Danube. It used to swim up the river even 2000 kilometers in huge groups coming from the Black sea. Some historical data prove the abundance of this fish species from that time. For example near Aszód plains – in Csallóköz – 77 sturgeons were caught during one day in 1553. People often caught sturgeons that weighed some hundred kilograms, what is more sometimes they found fish that were as heavy as 1 ton or more in their fishing nets.

The number of sturgeons started to decrease from the 16th century in Hungary, because of the intensive fishing methods. Hungarian fishermen caught them only a few times in the 20th century. The last sturgeon was caught in 1987 near Paks in Hungary.

We should think of the fact that while in the 1930s only two sturgeon catches were registered in the 417 km long Hungarian Danube section, at the same time people caught about 500 tons of sturgeon each year in the 955 km long Lower Danube, which equals to 50000 fish during one decade.

Two weirs were built near the Iron Gate section of the river Danube in 1970 and in 1984. These weirs are impassable for the sturgeons, so they can not swim up the Hungarian section of the river even if they sometimes try to do so. That is why many people think that making these weirs passable for fish is one of the most important tasks in the protection of acipenser species in the river Danube.

The extreme differences that were so apparent 70-80 years ago between the Hugarian sturgeon catches and the results of fishermen living around the Lower Danube can be traced back to the fact that by the beginning of the 20th century the former sturgeon spawning grounds and habitats had been radically changed by the river regulation works, which were started in the 19th century. Today acipensers are so rare even in the Lower Danube that their fishing has been forbidden lately in Roumania. "In my opinion, it is not the biggest problem that sturgeons can not swim up the Middle Danube because of the weirs near the Iron Gate. That is why making these weirs passable for fish is not the greatest achievement that we could do for the protection of acipensers living in the river Danube,” added Mr. Guti.

The protection of habitats is essential

According to Mr. Guti the following activities should be done in order to improve fish populations: "The rehabilitation of habitats – that have basic role in the ontogenesis of fish – is essential for the protection of biodiversity and the improvement of fish populations in the river Danube. We have to take professional hydrographic actions – that need to be supported by basic data for the initial planning phase – in order to maintain our Natura 2000 territories, to reach the good ecological state of our waters, and to develop the new approach of water management that is determined by the Water Framework Directive of the European Union. Therefore we have to set up an effective hydrobiological monitoring system. In my opinion, Hungary is underdeveloped, compared to the West-European countries in this aspect,” said Mr. Guti.

He especially emphasized the importance of the rehabilitation of fish habitats and fish biology researches that provide basic information for such activities. He mentioned several examples all around the world, which confirm the fact that the survival of river-fish species can be provided in the long run only if the destruction of their habitats is stopped. "That is why artificial fish settlings are only temporary solutions, and they are not sufficient enough to maintain fish populations in the future,” summarized Mr. Guti.

Shipping development vs. nature

River regulation works that develop shipping conditions on the river Danube have several effects on the rich flora and fauna of the river, on biodiversity and on the natural supply of fish. But the impacts that are caused by the increased volume of riverine traffic are much more dangerous.

"Besides the negative effects of riverine traffic I have to mention the considerable water backflow that is caused by the bigger ships. The speed of this flow is 4-5 times faster, than the swimming speed of young fish. Therefore the strong drifting kills many of these young animals. There are other negative effects as well. Bigger ships generate powerful waves that destroy the most productive water habitats, namely the shoreline and the plants, which live there. This way the natural self-cleansing system of the river is also damaged."

"Strong waves stir up the silt, which makes the water grumly. This has negative effects on plankton organisms, which are the most important foods of young fish. What is more, these waves disturb the spawning of fish species and the ontogenesis of young fish, which can lead to the decrease of natural fish supply,” emphasized Mr. Guti.