Rising temperatures affecting South Bohemia's traditional fishing industry
Traditional fishing has taken place in the waterways between Jindřichův Hradec, Tábor and České Budějovice for over a thousand years. This area is primarily where Czechia’s annual 20,000 tons of fish are caught, almost 90% of which are carp – the traditional fish eaten by Czechs at Christmas. But this centuries-old fishing tradition could be under threat – from climate change.
South Bohemia’s pond system, a large network of hundreds of ponds, rivers and canals in the flatlands around Třeboň, dates back to medieval times. Following up on an even older network of ponds and rivers which dates back to sometime around the 11th century, the current pond system started being created in the late 15th century and has been gradually built up since then. Nowadays, the landscape is listed in the UNESCO World Network of Biosphere Reserves.
But Ján Regenda from the Faculty of Fisheries and Protection of Waters at the University of South Bohemia told Czech Radio that a recent study pointed to the negative consequences of rising temperatures for the future of fishing in the region.
“Our colleagues warn that in 30, 40, 50 years’ time, heatwaves will be a regular occurrence, meaning that the water temperature in the ponds could rise above 25 degrees Celsius. And if the water stays at that temperature for more than a few days, that can obviously have a negative effect for the fish and what they eat.”
Another problem is the cleanliness of the water. Regenda points out that in most Czech ponds, the water is green or brown. This affects the oxygen levels in the water, which have to be just right for the fish to thrive.
“The amount of oxygen in the water is affected partly by the atmosphere, but mostly by photosynthesising algae. If the water is not clear, then light only reaches the top layer of pondwater up to about 50-80 centimetres – anything below that is in darkness. Oxygen is not created there, it is only consumed. So fishermen need to put greater emphasis on increasing the transparency of the water in the summer months, so photosynthesis can take place properly so as to avoid oxygen deficiency in the water, because that is what primarily hurts the fish – a lack of oxygen.”
However, he sees the biggest challenge in changing rainfall patterns – and says that the solution is better water retention and management.
“It can be expected that the amount of precipitation that falls in Czechia during the year will be the same, or will increase slightly according to some assumptions. What we need to change is the way we manage water. The Czech Republic is the roof of Europe. In fact, most of the water that falls here flows away from us, so we have to start retaining it more efficiently.”
However, overall Regenda remains surprisingly optimistic about the future of fishing in South Bohemia, pointing out that fish are farmed in countries with even hotter climates than Czechia.
“Fish, even carp, are farmed in southern Europe, Asia and northern Africa. So a fundamental change is not on the horizon, but with the arrival of climatic changes, fishermen will have to adapt how they work somewhat – for example, monitoring the water quality more often, reducing the number of fish, and giving more space over to natural production. So it will bring changes – but I don’t think they will be dramatic changes.”