Oxygen depletion alarms fishermen as Danish coastal waters lose fish

Oxygen depletion along Denmark’s coasts has reached alarming levels for the third consecutive year, with more than a third of the country’s 108 coastal waters affected so far this year, DR reports. Several coastal areas have no fish or very few fish left.

The figures come from the Danish Agency for Green Land Transformation and Water Environment. The Danish Society for Nature Conservation has compared the latest oxygen measurements from 40 locations with measurements from the same places over the past two years and described the results as alarming.

Fisherman reports 300 fewer trout

The effects are particularly clear along the coast of Helnæs Bay near Faaborg on Funen. Recreational fisherman Kent Andersen, who has fished there for many years, says he has never seen conditions this bad.

“It looks terrible. It has never looked this bad,” Andersen said. He said conditions had started to deteriorate significantly about five years ago, and that he had thought last year that they could not get worse.

Helnæs Bay was once considered one of the best places on Funen to catch trout, Andersen said, but he has not heard of anyone catching one there this year. He used to catch about 350 trout a year around Denmark’s coasts, but has caught only 50 this year.

Jens Würgler Hansen, a senior adviser at Aalborg University’s Institute of Ecoscience, said the fisherman’s assessment may be accurate. Oxygen depletion is developing quickly, particularly in waters around Funen, he said.

The current conditions involve severe oxygen depletion, which is the most serious category, according to Würgler Hansen. Denmark recorded its worst oxygen depletion ever in 2023, but that record was surpassed the following year. Conditions appeared to be heading in a similar direction in 2025, but strong winds in September slowed the development.

“It tells me that we still have a significant problem with our marine environment, and that a major effort is needed if we are to put things right,” Würgler Hansen said.

Experts point to nutrients and climate change

The figures come as debate continues over agriculture and its release of nitrogen into the marine environment. On Thursday, the Danish Parliament is due to give final approval to a law allowing much tighter regulation of agriculture’s nitrogen emissions.

Andersen said he was distressed by the direction of the development.

“Thirty or 40 years ago, you could not have dreamed of how it looked. There was life everywhere: garfish, cod and everything else. Now it is a desert. It really hurts me,” he said.

Würgler Hansen said the deterioration was being driven by two factors: excessive nutrients, including nitrogen, in Danish marine waters, and climate change. Rising sea temperatures encourage further oxygen depletion, while lower wind levels also contribute.

He called the combination “a really bad cocktail” and said regulating the flow of nitrogen into the sea was central to solving the problem.

“There is no way around making significant reductions in the amount of nutrients entering the sea. Most of them come from agriculture,” he said.

Christian Rabjerg Madsen (S), minister for Nature and Animal Welfare, called solving the oxygen depletion problem “a task that has to be done”, while acknowledging farmers’ frustration.

“It is a difficult task. I understand that this causes frustration in agriculture,” he said.

The minister said he was concerned about the figures and warned that oxygen depletion would continue unless the underlying problems were addressed. Nitrogen regulations are part of the green tripartite agreement reached by the former SVM government, but work by local green tripartite groups is currently paused because several farmers are dissatisfied with the process.