Fish Poisons for Anesthesia

I stumbled across a bizzarre video in my recommended videos feed on YouTube yesterday that shows a goldfish getting surgery on his head growth blocking his vision (Note: this video is not for people who are squeamish, although there is no blood):

The video was an interesting find overall, simply because it had no actual correlation with any videos in my watch history. I haven’t watched videos on fish or surgery, so to be recommended with a video featuring both was unusual. To be honest, while I was engrossed by the goldfish surgery, what made me keep watching was the maker, Colum’s Aquaponics’, use of clove oil to sedate the fish.

This brought two thoughts to my mind. The first was that clove oil has been recommended by traditional herbal medicine for toothaches. Typical application may have entailed chewing a clove or putting it between the gums and cheek next to the painful area. According to Colgate, clove oil has also been on the rise as a form of alternative medicine for oral pain in recent times as well [1]. Clove oil contains the chemical eugenol that is responsible for its anesthetic properties and is also used in refined form for modern dental applications [2]. Eugenol is a substituted guaiacol, making it related chemically to other plant compounds like vanillin though with very different effects [3]. Seemingly unrelated, this link between analgesia in humans and anesthesia in fish makes the use of clove oil to numb a surgery appear plausible to me, though a stretch.

Fig. 1: Eugenol, a fish anesthetic found in clove oil (Wikimedia)

The second was that in ancient Hawai’i, there was a method of fishing that involved lacing a stream or tide pool with a plant tincture to sedate the fish and cause them to float to the surface. The plants used included ‘ahuhu (Tephrosia purpurea) containing the fish toxin tephrosin and ‘akia (Wikstroemia oahuensis) [4(published in 1921, source must be treated as a work of its time),5]. Looking at some pictures of ‘akia on the internet, I immediately recognized the plant to have grown all over my elementary school campus back home. That’s pretty weird to think about, but it also makes me feel like I’ve missed out on an opportunity for some fun experiments.  

Fig. 2: 'Akia plant leaves and flowers ('Imiloa)

Hawai’i is not the only place to have practiced poison fishing, though in general the practice is considered destructive and paralleled to other wide-effect fishing methods like blast-fishing. And of course, the limited reach of poison fishing would be no match for the current global demand for fish. Yet while this fishing technique has been passed by in modern times, the plants and chemicals once used for fishing may now find new applications, namely in fish anesthesia for aquatic veterinary care.

I hope you enjoyed this short blurb on the interesting topic of fish anesthesia, and be sure to leave a comment and share your thoughts on the post. These past few weeks have been busy in school, and the first wave of midterms (UPenn doesn’t understand the term “midterm”) has started to hit. I do believe I will be able to post at least every other week, however, as seems to be my current posting schedule, so be sure to look out for future posts. As always, thanks for reading!