Trout On Meth: How Freshwater Contamination Can Get Fish Hooked On Drugs

Even low levels of methamphetamine in the water can cause brown trout to get hooked. Image credit: Kletr / Shutterstock.com

Human drug-taking is a bit of a puff, puff, pass situation for wildlife. We dose, we process, and then we pee it into the environment (hopefully not directly). Our wastewater regularly contaminates freshwater ecosystems, and so the drugs that we took to alter our biochemistry go on to alter those of the animals within that environment. A recent study found that antidepressants can embolden crayfish, influencing their caution in a way that could put them at greater risk of predation. While we needn’t feel guilt for consuming medications that we need to keep us healthy, it’s important to keep an eye on the implications of those medicines for the wider environment and try to mitigate their effects where we can.

The knock-on effect isn’t limited to legal drugs, either (remember the poor Thames eels’ cocaine problem?). New research, published in the Journal of Experimental Biology, decided to jump into the world of recreational drug pollutants in examining what the narcotic methamphetamine does to brown trout (Salmo trutta).

To find out, they isolated some trout in a tank that had been spiked with a concentration of methamphetamine to match that detected in freshwater rivers and left the fish to acclimate for 8 weeks. The trout were then taken out of their drugged tank and placed into an uncontaminated freshwater tank to see how (or if) withdrawal from the drug affected them. To try and identify if the fish were craving meth, every other day the researchers would give them a choice between an uncontaminated and contaminated body of water, a trial which carried on for 10 days.

Their hypothesis was that if the fish were in withdrawal, they would seek out relief by returning to the drugged water whenever possible. Sure enough, the fish’s choices revealed that those who had gotten “hooked” on meth were addicted and actively selecting the drugged water during the first 4 days after their move to the uncontaminated tank. These fish were also less active than their tank mates that had not experienced meth, and evidence of the drug was found in their brains up to 10 days after methamphetamine was withdrawn completely.

“Whether illicit drugs alter fish behaviour at levels increasingly observed in surface water bodies was unclear,” said Pavel Horký from the Czech University of Life Sciences Prague, Czech Republic, who fears that even the low levels of methamphetamine in our rivers could represent a considerable threat to the survival of the species they contain in altering their behavior as they seek out contaminated water systems in search of a fix. “The elicitation of drug addiction in wild fish could represent another example of unexpected pressure on species living in urban environments.”

 


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