Top Ten Facts about Seahorses

These odd creatures have long fascinated marine biologists

Author and marine biologist Helen Scales, Ph.D., said of seahorses in her book Poseidon's Steed: "They remind us that we rely on the seas not only to fill our dinner plates but also to feed our imaginations." Here you can learn more about seahorses - where they live, what they eat and how they reproduce.

Seahorses are fish

Sea horses

Georgette Douwma/Getty Images

After much debate over the years, scientists finally decided that seahorses are fish. They breathe using gills, have a swim bladder to control their buoyancy, and are classified in the Class Actinopterygii, the bony fish, which also includes larger fish such as cod and tuna. Seahorses have interlocking plates on the outsides of their bodies, and this covers a spine made of bone. While they have no tail fins, they have four other fins - one at the base of the tail, one under the belly and one behind each cheek.

Seahorses are bad swimmers


Craig Nagy / Flickr

Although they are fish, seahorses are not great swimmers. Seahorses prefer to rest in one area, sometimes holding on to the same coral or seaweed for days. They beat their fins very quickly, up to 50 times a second, but they do not move quickly.  They are able to move up, down, forward or backward.

Seahorses live around the world

Longsnout Seahorse

Cliff / Flickr

Seahorses are found in temperate and tropical waters throughout the world. Favorite seahorse habitats are coral reefs, seagrasses, and mangrove forests. Seahorses use their prehensile tails to hang out on objects such as seaweed and branching corals. Despite their tendency to live in fairly shallow waters, seahorses are difficult to see in the wild, since they can remain very still and blend in with their surroundings.

There are 53 species of seahorses

Pacific Seahorse
James R.D. Scott / Getty Images

According to the World Register of Marine Species, there are 53 species of seahorses. They range in size from under 1 inch, to 14 inches long. They are categorized in the family Syngnathidae, which includes pipefish and seadragons.

Seahorses eat nearly constantly

Yellow pygmy seahorse (Hippocampus bargibanti)

Wolfgang Poelzer/Getty Images

Seahorses feed on plankton and small crustaceans. They do not have stomachs, so food passes through their bodies very quickly, and they need to eat often.

Do seahorses pair bond?


felicito rustique / Flickr 

Many seahorses are monogamous, at least during a single breeding season.  A myth perpetuates that seahorses mate for life, but this doesn't seem to be true.

Unlike many other fish species, though, seahorses have a complex courtship ritual and may form a bond that lasts during the entire breeding season.  The courtship involves a "dance" where they entwine their tails​ and may change colors. So, although it may not be a long-lasting match, it can still look pretty enchanting.

Male seahorses give birth

Pregnant Seahorse

Kelly McCarthy / Flickr

Unlike any other species, male seahorses become pregnant.  Females insert their eggs through an oviduct into the male's brood pouch. The male wiggles to get the eggs into position. Once all the eggs are inserted, the male goes to a nearby coral or seaweed and grabs on with his tail to wait out gestation, which may last several weeks.  When it's time to give birth, he'll contort his body in contractions, until the young are born, sometimes over a period of minutes or hours. 

Seahorses are experts at camouflage

Pygmy Seahorse

Steve Childs / Flickr

Some seahorses, like the common pygmy seahorse, have shapes, sizes, and colors that allow them to blend in with their coral habitats. Others, such as the thorny seahorse, change color to blend in with their surroundings.

Seahorses are vulnerable to extinction.

Dried Seahorses, Malaysia

Stuart Dee / Getty Images

Seahorses are threatened by harvesting (for use in aquariums and Asian medicine), habitat destruction, and pollution. Because they are hard to find in the wild, population sizes may not be well-known for many species.  

Humans have reduced their use of seahorses

Seahorses have been a topic of fascination for artists for centuries, and are still used in Asian traditional medicine. They are also kept in aquariums, although more aquarists are getting their seahorses from "seahorse ranches" now rather than from the wild.