Why were farm-raised salmon in Germany seen acting erratically and jumping out of their tank’s water? Scientists say they were high on cocaine.

In June 2020, a foreman at the Lanuv Kirchhundem-Albaum site in Germany noticed the Atlantic salmon raised for an ecological conservation project frantically leaping up and thrashing around in an apparent effort to escape their tank. It was captured in photographs that show a mass of writhing fish suspended in the air. The strange behavior prompted an analysis of the local basin and inlet water by the State Environment Agency of North Rhine-Westphalia, which found it was tainted with cocaine. 

According to Der Spiegel magazine, other common contaminants including pesticides were found in the water, but the researcher’s main focus has been on the presence of cocaine.  Daniel Fey, the head of the agency’s ecology and aquaculture department, said that the salmon’s frantic jumping “was a response to a feeling of discomfort.”

The recreational drug was found in the stream that fed the tank but not the tank itself. The State Environment Agency’s annual report hedged that “a clear cause for the behavior of the fish could not be found. However, a reaction to the cocaine detected in the stream water cannot be ruled out.” Officials later looked into an illegal wastewater discharge into the same stream. 

Last month, F&S reported on a study that found brown trout can become addicted to meth. Those fish did not exhibit symptoms when they were on the drug, but they did appear to go through a period of withdrawal when it was removed.

According to a BBC Future article, sewage treatment plants aren’t able to filter out drugs very well. Some researchers are concerned that drug-addicted fish could sustain long-term changes in behavior that could span generations, but Fey told Der Spiegel that the salmon in Germany did not seem to suffer any permanent damage. The day after the jumping incident, they “showed typical behavior again.”