If you're wondering whether brown trout can become meth junkies, science has an answer for you. Czech researchers sought to determine whether the drugs used by humans—which end up in waterways because wastewater treatment plants aren't built to remove methamphetamine—could turn fish into addicts. The short answer: yes. To get there, researchers put 40 brown trout in a tank containing water with a meth concentration in line with what has been detected in freshwater rivers, reports CNN; another 40 were put into a control tank. Eight weeks later, the first group was moved to a drug-free tank. To test whether those fish entered withdrawal, the researchers offered them water with and without meth every other day. Over the initial four-day period, they picked the meth water.
Those fish were also observed to be less active than fish in the control group, and evidence of the drug was detected in their brains as long as 10 days after their last meth exposure, per an accompanying essay. "As such, our study identifies transmission of human societal problems to aquatic ecosystems," the researchers write in the Journal of Experimental Biology. Lead researcher Pavel Horký from the Czech University of Life Sciences Prague says addiction in fish could spur another potential problem, in that it might encourage the fish to seek out unhealthy water treatment discharges, which could further worsen their heath. If you're wondering if this is truly a problem, LiveScience cites studies that have found meth present in rivers around the globe, "with concentrations of the drug ranging from a few nanograms to dozens of micrograms per liter of water." (Read more discoveries stories.)