A recent study out of Brazil claims to be the first of its kind to show significant benefits from ingested CBD for fish kept in artificial environments.  The study was carried out on Nile Tilapia, a common fish in the aquaculture trade, worldwide.  The authors claim to have measured several beneficial effects after feeding the experimental groups prepared food pellets treated with varying amounts of CBD dissolved in a solution of soybean oil.  The food pellets for the control group were also treated with soybean oil alone.  According to the study authors one thing that set this research apart from past research that showed no or negligible benefit from the addition of CBD to fish feed was a dramatically increased dose across the board.  The researchers also found some counter-intuitive dose dependent effects.  

So what benefit did the fish in the study derive from CBD?  According to the authors, at a dose of either 1, 10 or 20 mg/kg yielded lowered cortisol (stress hormone) at baseline than the control group as well as decreased ventilation rate compared to control. Cortisol dropped more with an increasing dose.  At the 10 mg/kg dose, fish showed significantly less aggressive behavior but this was not the case at the 1 or 20 mg/kg doses.  All 3 dosing levels yielded lower stress induced ventilation rates compared to control in a dose dependent manner with 20 mg/kg being most effective in this metric.  None of the doses had a measurable effect on feeding or growth rates.  All of that sounds pretty good, so what about the bad?

Well, there were some potentially negative effects.  The size of the testes increased compared to control in all groups and this trend increased with dosage. However, the number of spermatozoa decreased in all experimental groups.  Interestingly, the decrease in spermatozoa was most pronounced at the lowest dose of 1 mg/kg and significantly less severe at the highest dose of 20 mg/kg.

The authors conclude that while more study is needed to understand the mechanisms behind these results and caution should be used with regard to tilapia that are reared for reproduction, the vast majority that are reared in close quarters for meat production can benefit from reduced stress levels without impacting feeding or growth rates negatively.  They view the results as a win-win for both fish and farmers alike.

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You can read the original paper here

Camargo-dos-Santos, B., Bellot, M.S., Guermandi, I.I. et al. Cannabidiol improves Nile tilapia cichlid fish welfare. Sci Rep 12, 17650 (2022). https://doi.org/10.1038/s41598-022-21759-3