Cocaine Made the Salmon Swim Farther
Cocaine contaminants in water affect salmon behavior, according to a new study from SLU (Swedish University of Agrarian Sciences). Salmon that had ingested cocaine swam more and spread out over larger areas.
Drugs in lakes and other bodies of water are a growing environmental problem that can affect both animal health and behavior. Previous research has mainly been conducted in laboratory settings, but in a new study from the Swedish University of Agricultural Sciences (SLU), researchers were able to track how young Atlantic salmon exposed to cocaine behaved in Lake Vättern.
The factor that had the greatest impact on the salmon’s behavior was benzoylecgonine, the most common breakdown product of cocaine. They became bolder than the other fish in the study.
They swam nearly twice as far and also spread out further across the lake. The fish in the control group moved about 20 kilometers from where they were released, while these continued to move away and were eventually about 12 kilometers from the control group, explains the study’s lead author, Jack Brand.
Overlooking environmental impact
The discovery is important because environmental and risk assessments typically focus on the parent compounds rather than the degradation products, he explains.
One of the conclusions is that these substances actually affect the fish’s behavior in the wild. This suggests that we are overlooking a potential environmental impact they are exposed to.
We do not yet know what effects these behavioral changes will have, but even small changes can affect how the fish, for example, forage for food and avoid predators.
More measures
The researchers believe that several measures are now needed, such as improved water treatment and promoting technologies or regulations that either remove drugs and their breakdown products from the environment or at least monitor them more effectively.
‘I think it’s very important to convey this to those working on water regulation and wastewater management and show that these levels of chemicals, which are often found in our waterways, can affect fish behavior in the wild.’
Jack Brand emphasizes that no one needs to worry about the fish’s health or that it would be dangerous to eat them one day.
The concentrations are very low, and they are already present in nature, so it’s not as if we’ve introduced something entirely new. These are also young salmon, far from the legal size, and by the time they’re big enough to eat, the substances will have disappeared long ago.
