Diving with Seahorses–Am I California Dreaming?

After diving for 2½ hours underwater in the murky Mission Bay in San Diego, I am starting to have doubts that there are any seahorses here. All that I’ve seen is algae, stingrays, and more algae. Checking my air gauge, it’s getting low and I decide that I have to get back to shore. Just before the water is shallow enough for me to stand, I can’t believe what I see in front of me. Could it be real? I had to pinch myself, twice.

The first seahorses found in California were reported in 1857. However, specimens were found very infrequently, with only 9 specimens recorded over the next 100 years. Starting in 1984 they have been found in surveys almost every year in various bays in the San Diego area. A specimen was even found in San Francisco, although that was an isolated finding.

The local dive community first found out there were seahorses in San Diego in October 2008 when a local diver Ruth Harris had one attach to her finger while cleaning a white sea bass pen.

There are at least 40 species of seahorses in the world, all in the genus Hippocampus, with new species being discovered every few years. The scientific name for the Pacific seahorse is Hippocampus ingens, which comes from the Greek words “hippos” for horse, and “campus” for sea monster. Part of our brain is called the hippocampus because it is shaped like a seahorse. The Pacific seahorse is one of largest species in the world, reaching 30cm in length, and is the only seahorse found in the Eastern Pacific Ocean. The range of the Pacific seahorse was previously Peru to central Baja, but now that has been extended to Southern California.

Seahorses are in demand all over the world, for traditional medicines and as aquarium pets, and most seahorse species, including the Pacific seahorse, are listed as vulnerable by the International Union for Conservation of Nature. Every year, tons of Pacific seahorses are caught, dried, and shipped to Asia. Let’s hope that doesn’t happen to the California population.

Seahorses in the San Diego bays appear to have few predators, and lots to eat. On my dives I noticed plenty of Mysid shrimp and tiny juvenile fish that the seahorse enjoys eating.

I started diving eelgrass beds to assist Dr. Milton Love at the University of California Santa Barbara with observing habitats for various juvenile fish species. Juvenile kelpfish, perch, and bass enjoy the calm, protected environment of the eelgrass beds. For several years it was not clear if seahorses were mating and breeding in San Diego waters. Recently, I was able to witness an extraordinary event that shed some light on the issue.

Last year a seahorse researcher was in town specifically to see Hippocampus ingens in the wild. I had offered to take him on a dive and try to find one, although I couldn’t promise him anything. An hour into the dive, I couldn’t believe my eyes. We had actually found one! It was a large specimen with a large belly. Then, the seahorse suddenly started thrusting its belly forward and back.

Before my eyes, several tiny seahorses emerged and quickly swam away. The seahorse was giving birth! Although the event happened too fast to record in our cameras, we will never forget witnessing such a wonderful event. Seahorses usually give birth to hundreds of young, although the vast majority do not survive to adulthood. The seahorse is one of the only types of animals where the male gives birth to the young, not the female. The female deposits eggs into the male’s pouch, and the male seahorse fertilizes and incubates the eggs.

Pacific seahorses preferred habitat is the green eelgrass Zostera marina, and a brown algae in the Gracilaria genus. I spoke with Dr. Kimo Morris about its natural history and environment. “The three dimensional environment of the eelgrass and Graciaria acts as a biological facilitator for many organism, including the seahorse. This is also why artificial reefs work. Fish enjoy the protection of a 3-D environment. The presence of the seahorse is an anecdotal indicator of the recovery of the eelgrass habitat. The fact that we are finding them there is a great sign.”

Hippocampus ingens blends in well with the Gracilaria algae, and when approached will put its head down to the bottom to avoid being seen. They are expert lie-in-wait predators, staying still and sucking in small prey as it passes by their toothless mouth.

As our waters in California continue to improve, could divers start finding the Pacific seahorse further north in eelgrass beds? Only time will tell. In the meanwhile, don’t be surprised if one day you are underwater, and find something wrapped around your finger.

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