What’s up with Seahorses on Koh Tao?

Seahorse SaiNuanKeep your eyes open, according to locally collected citizen science data April is the month to see seahorses on Koh Tao. These sightings are not as common as you might think, and each observation is an invaluable piece of information in understanding the puzzle of these shy, curious creatures’ populations that are hiding out there in the waters around our island. We began our seahorse studies in 2012, and since 2013, the community of Koh Tao has been working with iSeahorse.org to track and monitor seahorse populations as observed by divers. Any divers who see a seahorse either underwater or even washed up on the beach are able to report their sightings to the site, or to iNaturalist.org. After 7 years of data collection, we are starting to see some interesting trends.

iSeahorse.org Data Summary for Koh Tao

Observations are broken up by region and then by site. For our region in SE Asia, the most observed seahorse is the Hedgehog Seahorse (H. spinosissimus) and is mostly observed in March and April, with sightings all around the Gulf of Thailand. There have been 21 reported observations on Koh Tao, mostly by Tine Kinn Kvamme and Pau Urgell. The next most prevalent species in the region is the Tiger Tail Seahorse (H. comes), with the largest peaks in observations in April, but smaller peaks in January and October. There are only 2 observations from Koh Tao, however these are disputed, and it is unconfirmed wiether or not Koh Tao has the Tiger Tail Seahorse.

The third most abundant seahorse in the region is the Common Seahorse (H. kuda), with an impressive 8 observations on Koh Tao, mostly by Tine Kinn Kvamme and Rahul Mehrotra. This seahorse was spotted mostly in March and November, and is a tough one to spot due to its small size. The fourth most abundant seahorse is the Three-Spot Seahorse (H. trimaculatus) seen mostly in April, with a smaller peak in June. There have been 4 observations reported from Koh Tao, by Pau Urgell and Chad Scott. The most rarely sighted species in the region is the Great Seahorse (H. kellogi) which has been seen twice on Koh Tao, once by Andreas Fiskeseth and Pau Urgell.

Previously, we published a summary of our own data collection, which showed that 2015 was 'the year of the seahorse' in regards to our own sightings, with 34 individuals sighted in just a few months, mostly in Sai Nuan.

dead seahorses Why is this work important?

All of the seahorse species discussed above are listed as vulnerable under the IUCN. Seahorses face a variety of threats, most saliently the threat of overfishing and collection. Seahorses are in high demand in countries such as China and Taiwan for there value in traditional medicine (with no scientifically proven benefits), and Thailand is one of the world’s major suppliers to that trade, and Koh Tao is no exception to that. In 2016, one of our interns discovered a bottle during a beach clean-up which contained 3 dead seahorses, along with some pieces of fruit. Furthermore, seahorses are affected by the same problems that are affecting most other animals on the reefs, including habitat destruction and climate change. As such, they are an important bioindicator of the health of our oceans, and act as the ‘canary in a coal mine’ to warn us about the impacts we are having on our marine ecosystems and resources.

How to Contribute

As a community, we have identified a total of 4 (possibly 5) species of seahorses, although when we began in 2014 we thought there were only 3 species here on the island. Our observations have already contributed to publications by iSeahorse.org researcher Lindsay Aylesworth and others. This project is still young, but has already proven itself to be both interesting and valuable. We want to take this opportunity to remind and encourage folks to report their seahorse sightings to iSeahorse.org and continue to contribute to this great project. So, keep your eyes open, report your observations, and let’s help save seahorses together


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New Heaven Reef Conservation Program