Animal deaths in cold weather

Hundreds of fish dead in pond at Linz University

The university pond in Linz is mainly home to exotic ornamental fish that had been released there illegally(Bild: Klemens Groh)

Hundreds of dead fish have been floating in the pond at Johannes Kepler University Linz for days. The cause of the animal deaths is likely to have been the freezing cold of the past few weeks. It is mainly ornamental fish and goldfish that have not survived the icy temperatures. They had apparently been released illegally. 

The full extent of the tragedy in Linz's Uniteich only became apparent with the current milder temperatures. As the ice layer melted, it became clear that hundreds of fish had died in the more than 11,000 square meter pond during the last cold spell.

Released illegally
However, most of the victims of the cold were goldfish or ornamental fish that had apparently been illegally released there by aquarium owners and had multiplied unchecked.

"The pond was drained, dredged and cleaned in 2015. After that, we did not introduce any more fish," emphasizes JKU Vice Rector Alexander Freischlager.

In addition to small aquarium fish, there were also koi carp in the facility. However, these did not fall victim to the fish mortality. "The small species - mainly silver-colored Caribbean fish with blue and green stripes - probably froze to the ice cover and died, the larger ones were probably spared because they are at a different water depth," says the vice rector.

This year, the pond was frozen over longer and more severely than in previous years. The ornamental fish probably froze to the ice.

Alexander Freischlager, Vizerektor der Johannes Kepler Universität Linz.

Food for birds
The fish carcasses are now to be collected quickly and disposed of properly. However, some of them have probably already served as a welcome meal for birds. Freischlager: "Among others, a flock of seagulls has been spotted."

To be on the safe side, the university also ordered water samples to clarify whether there had been a worrying increase in germs.