NOVI SAD, Serbia — Small boats stand idle on cracked ground in a shriveled side channel of the Danube River in northern Serbia, where the water has receded into a couple of shrinking ponds under pressure from extreme drought and heat. Fish circle in the shallow waters.

“This is all we have, these two little ponds that are full of juvenile fish,” fisherman Dusan Jovanovic said. He said the fish are in danger because there is too little water and its temperature is over 30 degrees Celsius (86 degrees Fahrenheit).

“If they start to die, they will all die at once,” Jovanovic said.

Persistent drought and scorching heat this summer have ravaged ecosystems and businesses across the region, from a lake in Slovenia and the side channel of the Danube in Serbia, to fish farms in Bosnia, the Czech Republic, Romania and Hungary.

The fish industry has been hit especially hard, with damage estimated in the millions of euros (dollars). This is adding to the already high toll caused by problems with energy and water supplies, devastated crops, losses in river traffic and trade.

Finding themselves unprepared for this year’s crisis, countries and businesses are now pondering ways to minimize the effects of future extreme weather events that scientists have tied to human-induced climate change.

Around 99% of Hungary’s lands are currently under severe or extreme drought conditions, according to the national meteorological service. Desertification, a process where vegetation recedes because of high heat and low rainfall, threatens much of the Great Hungarian Plain.

Among the most affected are Hungary’s roughly 27,000 hectares (67,000 acres) of fish ponds. The country’s Agriculture and Food Economy Ministry said last week that “persistent heat and water shortages” had led to 1,588 hectares (3,924 acres) of those ponds drying out, causing the deaths of nearly 280 metric tons of fish at 20 farms.

The estimated revenue loss from the damage was 1.3 billion forints ($4.2 million), the ministry said. Producers say replacing lost fish could take years. Sometimes, operators were forced to drain one pond and divert its water to save fish in another, the Hungarian Aquaculture and Fisheries Inter-branch Organization said in early August.

For fish farmers in Romania, especially those cultivating carp, this year’s blistering heatwave follows severe droughts in 2023 and 2024, the effects of which are still being felt, says Catalin Platon, president of ROMFISH National Association of Fish Producers.

In carp production, Platon said, the production cycle is three or four years.

“So what we lost in 2023 has (had an) impact every year since,” he explained. Water-use policies that prioritized irrigation for agriculture during the previous droughts, “left us with no water for the fish,” Platon complained.

Fish farmers across the Czech Republic have taken various emergency measures: reducing or suspending feeding to reduce oxygen use, aerating the ponds or draining them when necessary.

The Czech Fishing Association officials say sustained rainfall could ease the immediate crisis, but long-term measures are needed to retain more water in the landscape.

Jan Sokolik, a technician at the Rybarstvi Trebon fishery, explained that “some ponds that were actually low on water have already been fished, but they were all marginal ponds.”

“Now we’re just starting to plan what to do with the big ponds,” he said.

Veljko Budjen owns a trout farm near Trebinje in southeast Bosnia. He said hot and dry summers have brought serious problems in the mainly mountainous country famous for its trout restaurants.

“Trout is a cold water fish, which requires cold water with a lot of oxygen,” he said. “So during the summer you are forced to reduce trout production and feeding so the business can just barely survive.”

One option, he said, is to add liquid oxygen to the water during summer months. Otherwise, he said, “you wait for the first rain.”

Emergency teams have been pumping water into Lake Pristava in eastern Slovenia, a favorite spot for fishermen, to try to prevent a mass suffocation of fish from lack of oxygen and water chestnut overgrowing to cover the lake surface.

Firefighters have pumped in 8 million liters (2 million gallons) of water but they still fear it’s not enough.

“We are surprised that any fish has survived at all,” Danijel Fras, from the Pesnica Lenart Fishing Association, told public broadcaster RTV Slovenia.

In Serbia, fishermen said the only solution for the endangered fish in the Danube side channel in Novi Sad is to move them to another location.

“The temperatures this year are extreme,” Jovanovic, the Serbian fisherman, said. “No one can remember anything like this.”

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Justin Spike in Budapest, Hungary, Eldar Emric in Trebinje, Bosnia, Stanislav Hodina in Prague and Steven McGrath in Leamington Spa, England, contributed.