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Hawaiian Marine Life Profiles: Fish

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Common Name:

Fisher's Seahorse

Hawaiian Name:

mo o lio

Scientific Name:

Hippocampus fisheri

Found in Exhibit:

Mid Reef



If a man ever became pregnant and gave birth to 100 babies-or even one baby, the event would make headlines around the world, and women everywhere would probably stand up and cheer.

For the three-inch high Fisher's seahorse-the most common but rarely seen seahorse in Hawaiian waters-such a miracle is just the normal way of doing things. Males of all species of seahorses become pregnant, carry the eggs of their young for a gestation period of 10 to 50 days, and give birth to anywhere from 100 to 300 babies.

Seahorses are monogamous, at least for a single breeding season, but some mate for life. Each day, just after dawn, the mated pair will greet each other with a graceful dance lasting for up to 10 minutes. The couple then separates for the remainder of the day. They are believed to mate during a full moon, at which time they may utter musical sounds and even change color.

The act of mating consists of the female depositing her eggs into the brood pouch of the male through a long tube called an ovipositor. The female then swims away, her job finished, and the male fertilizes the eggs, which eventually become embryos. He carries, nourishes, and cares for the embryos until they develop into tiny seahorses. The male "gives birth" by pumping his tail to expel the babies. Labor can last as long as three hours. Newly hatched seahorses must rise quickly to the surface where they gulp a breath of air that enables them to remain upright.

The Fisher's seahorse is one of thirty-five known species belonging to the Syngnathidae family that includes pipefishes, pipehorses, and seadragons. Seahorses worldwide are found in the tropics or along temperate coasts. They are true bony fishes with curved trunks, heads resembling the head of a horse, and prehensile tails capable of grasping and holding onto strands of seaweed or algae. Their dorsal and pectoral fins are usually transparent. The dorsal fins-beating almost as fast as a humming bird's wings-propel the seahorse through the water, while the pectoral fins control turning and steering. Seahorses often swim in pairs with their tails linked together, but they cannot curl their tails backwards.

In the wild, seahorses feed on miniscule living creatures such as daphnia, crustaceans, brine shrimp, and the larvae of water insects. Their elongated, tubular snouts function as straws, enabling them to suck in their nourishment. They have no stomachs, and their inefficient digestive systems require surprisingly large quantities of food for their size.

Prior to being granted international protection in May of 2004, at least 20 species of seahorses were harvested for traditional Chinese medicine at the rate of 24.5 million individuals per year. Loss of habitat and the aquarium trade endangered many more.

Too little is known about Hawaii's Fisher's seahorse to determine its survival status. Spotting this golden-orange, red or pink seahorse with blackish mottling in the open ocean is a magical moment for anyone-but especially for enthralled humans who wonder what it might be like to retool their biological destinies and assume the duties of the opposite sex. The tiny male seahorse could teach its human male counterparts a thing or two about being pregnant and giving birth.

PDF: fishers_seahorse.pdf