Just keep swimming кракен

For the new study, the scientists performed trials with more than 700 young salmon, or “smolts,” in the laboratory and in the field. The research team used sound-transmitting tags to remotely track hundreds of smolts in 2020 and 2021 as the fish navigated the Dal River in central Sweden.

Migrating smolts swim downriver into a reservoir, hurtle over rapids and crest two dams before finally reaching the Baltic Sea. The journey takes 10 to 13 days. Two major classes of pharmaceuticals — benzodiazepines and opioids — “are commonly detected in rivers and streams worldwide, including in Sweden, where our study was conducted,” Michelangeli said.

Time-release implants in the smolts dispensed two drugs from these classes: clobazam and tramadol. Fish received clobazam, or tramadol, or both. A control group of smolts received implants with no drugs in them at all.

“These two drugs are known to interact chemically when taken together in humans, and they often co-occur in the environment,” Michelangeli said. “This made them a good test case to explore how pharmaceutical mixtures might affect animal behaviour.”

Along with the field trials, the scientists ran a laboratory-based study on 256 smolts to confirm that the implants worked as intended and that the drugs were lingering in the fishes’ bodily tissues and brains.