Researchers from the University of the West of Scotland, working alongside scientists from the Waltham Petcare Science Institute, part of the global food company Mars, have conducted the first known study to examine how cannabis derived compounds affect fish during transport.
The research focused on variatus platys, a species commonly found in the ornamental fish trade. Over a 30 minute transport period, groups of fish were placed in water containing different concentrations of CBD. The goal was to see whether the compound could reduce stress during one of the most demanding stages of the fish trade.
The results were striking. Fish transported in water treated with CBD showed noticeably calmer behavior compared to untreated fish. Researchers observed fewer stress related actions such as biting, chasing, and erratic swimming immediately after transport, as well as 30 minutes and two hours later. These calming effects were most pronounced at a mid range CBD dose, which appeared to strike the optimal balance.
Fish exposed to this mid level dose also displayed smoother movement patterns, traveled shorter distances during observation, and spent less time immobile during individual behavioral testing. Together, these changes pointed to a significant reduction in transport induced stress.
Professor Katherine Sloman from the University of the West of Scotland emphasized the broader implications of the findings. She explained that improving fish welfare during international transport is important not only from an ethical standpoint, but also from an economic one. Stress during transport often leads to aggressive or erratic behavior, which can increase anxiety levels and result in physical injury.
She added that the study suggests a simple adjustment to current transport practices could make a meaningful difference. Adding CBD to commercial water conditioners, she said, has the potential to transform the ornamental fish industry and protect the wellbeing of millions of animals.
The stakes are high. An estimated one billion exotic fish are transported globally each year across more than 125 countries. During transport, fish frequently experience intense stress, which can manifest as abnormal swimming, increased heart rate, hiding behaviors, reduced feeding, and aggression toward other fish.
This stress does more than affect behavior. It can weaken immune responses, leaving fish more vulnerable to disease. Injuries caused by anxiety driven aggression may also require fish to be quarantined and treated before they can be sold, creating additional challenges for breeders and retailers.
To conduct the study, researchers selected small groups of five fish from a population housed across 221 tanks. Each group was placed into a sealed transport bag containing one liter of water made up of equal parts fresh water and water from their original tank. The bags were then assigned to one of five treatment conditions.
Three of the treatments included water conditioners containing different CBD concentrations, while two served as control groups. Each treatment group included eight transport bags, ensuring consistency across the experiment.
Dr Donna Snellgrove, fish research manager at the Waltham Petcare Science Institute, said minimizing stress during transport is critical to maintaining fish health throughout the trade. She noted that the team is proud to help establish scientifically supported solutions that could positively impact a vast number of animals worldwide.
The study, published in the journal Applied Animal Behaviour Science, also explored how CBD may work at a biological level. Researchers found that CBD may influence neural pathways associated with fear and anxiety, without damaging the protective mucus layer that covers fish skin. This is especially notable because fish, like mammals, possess an endocannabinoid system.
Previous research has already shown that CBD has anxiety reducing effects in humans and animals. In one recent multi year analysis involving more than 47,000 dogs, animals given CBD supplements showed consistently lower levels of aggressive behaviour as they aged. This growing body of evidence suggests CBD’s calming effects may extend across species in ways scientists are only beginning to understand.
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