Crystal Meth in waterways is turning Trout into drug addicts

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Fish get addicted to meth in polluted rivers, go through withdrawal



Live Science

Fish can get hooked on meth that washes into their freshwater homes, to the point that they actively seek out the stimulant, a new study suggests.

After being used by humans, methamphetamine enters waterways through sewage systems and discharges from wastewater treatment plants. "Where methamphetamine users are, there is also methamphetamine pollution of freshwaters," first author Pavel Horký, an associate professor and behavioral ecologist at the Czech University of Life Sciences Prague, told Live Science in an email.

Meth pollutes rivers all over the world, with concentrations of the drug ranging from a few nanograms to dozens of micrograms per liter of water, according to reports in the journals Chemosphere and Water. Given the global prevalence of meth in waterways, Horký and his colleagues wondered whether fish might get hooked on these small doses of the drug.

The team's new laboratory study, published Tuesday (July 6) in the Journal of Experimental Biology, suggests that yes, even minuscule amounts of methamphetamine could be enough to cause addiction in freshwater fish, the team concluded.

That said, an expert told Live Science that, even though the fish in the study sought out meth-tainted water, that may not be enough evidence to say they are truly "addicted."

"I'm not sure you can truly say these fish are addicted to methamphetamine, but they certainly show a preference for the compound … which they shouldn't, really," said Gabriel Bossé, a postdoctoral research fellow at the University of Utah who was not involved in the study; Bossé uses zebrafish as a model to study complex brain disorders and recently developed a technique to study opioid-seeking behaviors in the fish.

In regards to the new research, "it seems that the preference for meth dies down after just a few days," whereas if the fish were truly addicted, he'd expect that preference to persist over a longer period of time, he said. "Whether you call it addiction or not, you can argue, but it's clear that methamphetamine changed how these animals behave," and those effects could potentially hinder their ability to find food, avoid predators and reproduce in the wild, Bossé noted.

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The researchers also noted that, in general, the meth-exposed fish became somewhat sedentary in these first four days of withdrawal, while the drug-free fish swam about as usual. This lack of movement hinted that the fish were stressed out due to their meth withdrawal, the authors suggested; scientists have seen similar behavior in zebrafish that were experiencing withdrawal from opioids, according to a 2017 report by Bossé published in the journal Behavioural Brain Research.

To get better insight into these behavioral changes, the team took samples of the fishes' brain tissue and screened them for both methamphetamine and amphetamine, a metabolic byproduct of the drug.

They found that "there were differences in concentration of amphetamine and methamphetamine that were shown to be related to changes in behavior," Horký said. The amount of amphetamine in the brain, which would indicate a past exposure to meth, correlated with the subdued swimming behavior seen in the trout experiencing withdrawal. Conversely, methamphetamine appeared in the brains of fish that chose to swim in the drugged water during the behavioral experiment; this acute exposure correlated with an uptick in swimming, again hinting that the meth offered relief from withdrawal in addicted fish.

Taken together, these results suggest that, in the wild, brown trout could become addicted to trace amounts of meth in rivers and potentially congregate in areas where the drug accumulates, the authors reported. Such "unnatural attraction to one area" could not only disrupt the fishes' migratory patterns but also undermine their success in foraging for food or finding mates, they wrote.

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