Is there really such a thing as a freshwater seahorse?

830f03da-73f4-479e-92f4-e241b60ce48d

Editor's Picks
Sometimes pricy, sometimes cheap. Credit: Shutterstock
Features Post
Are fish really worth the price?
07 November 2019
Readers Tanks Post
Your tanks: Mark Allison
30 October 2019

Freshwater seahorse — real or just a myth? Heiko Bleher explains...

I’ve searched for freshwater seahorses for years. I even went to Lake Maracaibo and looked for the one described from the Mekong without any success.

It was described by Roule in 1916 as Hippocampus aimei, but no fisherman has ever seen one.

In a museum in Paris I looked at type specimens and in each was a nail hole! When Roule arrived in Laos he saw them nailed to the hut of a fisherman who told him they were from the Mekong.

After my museum discovery others became aware and Lourie et al revised it in 1999 and found that Roule’s two ‘freshwater’ seahorses were marine species — H. spinosissimus and H. barbouri. Both come from the Indo-Pacific: the former also being found in shallow estuaries of Thailand and the latter in estuaries of the Mekong.

The third seahorse I went after might be the only freshwater one on earth. It lives, or has lived, in Titikaka, the world’s highest navigable freshwater lake. I found the specimen pictured in the Museum Tiwanaku near the lake.

Something strange happened during my last visit. I climbed the highest island in the lake and at nearly 4,600m/15,000’ above sea level met a man claiming to be 120 years old and he recognised my photograph immediately, saying: “Yes, it lives here”.

He explained where he had seen it a long time ago, but the location was on my unexplored Peruvian end of this lake and I had no time to investigate as my flight out was due next day.

If the introduced trout and salmon and escaped exotics have not made the only freshwater seahorse extinct in the lake, as they have already with many endemic Orestias species, we might one day be lucky.

Polansky’s 1943 specimen from the lake, the sample at the Museum Tiwanaku labelled as Hippocampus titicacanesis (pictured above) is proof that there was a freshwater seahorse.