Researchers use psilocybin to reduce aggression in mangrove rivulus fish

Researchers have discovered that low doses of psilocybin, the psychedelic compound found in magic mushrooms, can calm highly aggressive mangrove rivulus fish without disrupting their normal social interactions. In a controlled laboratory study, the team observed a marked reduction in aggressive attacks after administering the compound to groups of fish that typically display intense territorial behavior. The findings suggest that psilocybin may selectively dampen escalating aggression rather than suppressing all activity.

The study comes at a time when scientists are exploring the broader effects of psychedelics beyond human use. Aggression in fish is a common issue in aquaculture, leading to injuries, stress, and reduced yields. By contrast, the research on psilocybin has largely focused on mood and anxiety disorders in humans. The team aimed to understand whether the compound’s calming properties could translate to non‑human species, offering a potential tool for managing aggression in aquatic environments.

In the experiment, 120 mangrove rivulus fish were divided into control and treatment groups. The treatment group received a low dose of psilocybin dissolved in their tank water. Over a 48‑hour observation period, researchers recorded the frequency of aggressive encounters, noting a 35% drop in attacks compared to the control group. Importantly, the fish maintained normal schooling and feeding behaviors, indicating that the compound did not broadly suppress activity. The researchers used video tracking to quantify aggression and confirm that the reduction was consistent across different pairs and group sizes.

If the results hold in larger, more natural settings, psilocybin could become a novel approach to reducing fish aggression in farms and research facilities, potentially improving animal welfare and productivity. The team plans to test higher doses and longer exposure times, and to investigate whether the calming effect persists in wild populations. Further research will also explore the underlying neural mechanisms, which could inform the development of targeted treatments for aggression in other species, including humans.