The seahorse is about the most bizarre fish that is native to Hawaiian waters. They are seldom seen because most seahorses throughout the Pacific Ocean live in calm water and due to the lack of outside barrier reefs here in Hawai‘i we do not have a lot of calm water. Over a period of 10 years diving every week, I have only seen three of these eight-inch-long fish — one yellow, one brown and one black. We have several seahorse species here in Hawai‘i, but the smooth seahorse is the most-common, and it lacks spines on its skin.
The seahorse has a long, tubular snout with a round, toothless mouth. Normally they remain motionless, holding onto coral, rocks or seaweed with their prehensile tail. When a small swimming shrimp comes close to them they move with lightning speed and suck the shrimp into their mouth for a meal. When disturbed they will let go of the bottom and swim upright using a tiny fin on their back to propel themselves forward. They swim slowly so they have to rely on blending into the reef so they are hard to see so they do not get eaten by predators.
Some of them in calm lagoons will even be covered in algae and sediment so it is extremely hard to see them.
The most unusual thing about the seahorse is the males bear the young. The females lay their eggs on the males’ bellies in a specialized pouch, then they leave the male to incubate and hatch the eggs. That takes about 20 to 30 days. The seahorse is the only Hawaiian fish species that has what looks like pregnant males. When the baby seahorses hatch they look just like miniature versions of the adults, and swim off quickly to go on their way and find a new home on the reef.
It is always a treat to find one of these special creatures while diving here in Hawai‘i, but on the tropical reefs in the Philippines and other Pacific islands they are quite common.
There have been a few times over the past 20 years that there will be a large number of seahorses hatch and grow in one small bay or lagoon, but usually the big surf thins them out within a year or so.
You can see the Hawaiian smooth seahorse in action up on the educational web page, underwater2web.com, in the movie “The World’s Guide To Hawaiian Reef Fish,” and also see over 100 of underwater marine-life movies on the YouTube channel at Underwater2web.
Terry Lilley, a marine biologist, lives in Hanalei. His websites include underwater-2web.com and gofundme.com/5urrm4zw.