The seahorses of Malaysia’s Sembilan archipelago

By Julia Lawson

A pregnant male yellow seahorse (H. kuda)

A pregnant male yellow seahorse (H. kuda)

Located roughly 10 km off the west coast of mainland Malaysia, Pulau Sembilan (or the Nine Islands) has managed to fly under the radar while the rest of the country expands and develops. The archipelago is composed of nine uninhabited and densely forested islands.

Earlier this year, I conducted an exploratory dive in Pulau Sembilan looking for seahorses, which I heard could be found in the coral reefs surrounding these islands. Threatened by coastal development, land reclamation, and fishing, these reefs comprise some of the last healthy coral populations off the west coast of Malaysia.

The first few days of the trip were eye-opening for the sheer scope and diversity of the corals on display, but disappointing in terms of seahorse sightings. My research assistant, Yin Sing, and I found only four seahorses in the first three days. While it was exciting to observe these charismatic and mysterious animals in the wild for the first time, my heart sank as we looked for others. There were none, but this was not surprising as seahorses populations are notoriously patchy and low-density.

During our very last dive, I swam slowly back to the boat, determined to enjoy my final few minutes underwater in spite of our disappointing numbers. I noticed some beautiful branching coral in the shallows and swam over to examine it. That’s when I noticed two eyes staring up at me. A tiger-tail seahorse seemed to hold its breath, wishing for me to pass by it unnoticed. Nearly perfectly camouflaged against the yellow-tinged Acropora coral, I strained my eyes to look for others nearby. I was shocked to find more seahorses, woven amongst the branching coral. Running out of time, I conducted a quick count and confirmed five individuals in this small patch. Had they been there all along and we were just looking in the wrong places?

We returned to the Sembilan archipelago a few weeks later, determined to find out as much as we could about our newly discovered seahorse population. We were equipped with quadrats, transects, calipers and all the other scientific gear needed to survey a population of seahorses. On a hunch, I felt like there had to be more than just the five I found in that small patch. We had three full days to find out if this was true. My mind raced—what if there were only five? What if we can’t find them again? But before I knew it, I was back in the water at the Sembilan archipelago, eye to eye with a tiger-tail seahorse. 

Yun Sing and I worked methodically, focusing on patches of branching coral and then finding seahorses living inside. We would locate a seahorse, gently measure and photograph it, and return it to its home. We would also note whether it was pregnant or had a partner (as seahorses are monogamous). Lastly, we took note of the seahorse’s surroundings by photographing and measuring the branching coral that it lived in.

After three days of intensive diving we found 78 seahorses around the Sembilan archipelago, including two tiny juveniles that were only 2.5cm in length. We were ecstatic to find out that this population represented not only the biggest population found to date on the west coast of peninsular Malaysia, but one of the biggest populations discovered thus far in South East Asia.

Despite the size and density of this population, we were surprised to learn that the Sembilan archipelago is offered no protection by the Malaysian government. With no restrictions on fishing, the Sembilan archipelago is open access and more alarmingly, it is open to those specifically harvesting seahorses for the aquarium trade. 

Project Seahorse has since then teamed up with Reef Check Malaysia, a local non-governmental organization in Malaysia, and our colleagues at the University of Malaya, to encourage government protection of this unique and important ecosystem. Protecting the seahorses of the Sembilan archipelago is an important step in maintaining seahorse populations in South East Asia.

Julia Lawson is an MSc student with Project Seahorse.