Seahorse Frequently Asked Questions

Do you have a basic question about seahorses or their relatives? We might have the answer here. And if we don’t, feel free to send your questions to us!

Reproduction

How many babies does a seahorses have a year?

I don’t believe anyone has studied this particular question in detail. Some species of seahorse have many babies at one time (1600 or more) and some have a small number (as few as a half dozen). Some seahorses breed all year round, and some only breed during the summer months. Some have young as frequent as every 10 days, and some have them around 30 days.

How many survive is another question. It’s thought that as little as 1 in 1000 (or .1%) survive in the wild. In captivity though, some breeders can achieve up to a 95% survival rate. And in captivity, some seahorses which are only seasonal breeders in the wild can breed all year.

Because there is no specific answer, lets just take a seahorse that produces a lot, for a long time. The Brazilian Seahorse Hippocampus reidi can produce up to 1600 young for 6 months out of the year, producing young every 15 days. In theory, one male seahorse could produce 19,200 babies in one year. However, a more reasonable estimate is around 500 young at any time, and they have been found to miss a few cycles now and then. So a more likely number is around 4000-5000. Still, the latter number is possible and in the Pacific Giant Seahorse Hippocampus ingens, a single brood containing over 2000 babies was recorded. Wow!

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How tiny are seahorses when they are born?

Seahorses are very small when they are born. It varies from species to species, but all of them are tiny. The smallest we know of are around 4 mm (about 1/64 of an inch), born to Pygmy Seahorses, and the largest is 1.8cm (just under 3/4″), born to Pot Belly Seahorses. We also don’t know the size of the babies from the absolutely smallest pygmy seahorses, so the babies could be even smaller!

Baby seahorse by adults tail.

Newborn brazilian seahorse by the tails of the mom (middle) and dad (background). The baby is approximately 7mm.

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Why does the male seahorse give birth?

This is an interesting question, one that has a lot of possible answers. The first answer is sort of a question – why is it that females give birth? In mammals, we’ve evolved where the female has glands that produce food for the young, so it only makes sense that she be involved in the gestation and nurturing of the embryo. However, in non-mammalian  animals, the role of female as primary care taker is much more blurred, because after producing eggs or giving birth, there is no physical limitation to which gender takes care of the young. In fact, in many non-mammal species, the males take over the primary care of the young.

Ostriches  are a great example where the male takes care of the young. The female does lay the eggs, and helps with incubation, but the male cares for and defends the chicks. This is “role-reversal” is not much of a reversal at all – because non-mammals have more options for rearing the young, it’s common for males to take over the job of rearing the young to protect his genetic investment. This happens in insects,  fish, amphibians, and birds. It’s downright common in fish  [pdf].

Seahorses have just taken this paternal care to the next level. They have evolved to have a pouch that actually encloses the eggs, and have tissue that performs the functions similar to a placenta. The female still lays eggs, but they are deposited directly into the males pouch. Females help out in an additional way though – they produce more eggs than can be fertilized. The male then absorbs those eggs, and gains nutrients from them for both himself and his growing brood.

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Is it hard to raise baby seahorses?

As far as marine fish go, they’re fairly easy. That being said, raising marine fish is in and of itself a difficult task. So they’re on the easy end of the spectrum in a difficult discipline. How difficult they are to raise also depends on the species. Some species are born larger and need less assistance when first born, while others need special very tiny food. The easiest are probably the Dwarf Seahorse Hippocampus zosterae, followed by the Lined Seahorse, Hippocampus erectus. Difficult species include the Brazilian Seahorse Hippocampus reidi and the Pacific Seahorse Hippocampus ingens.

You can read more about raising seahorses in our section on breeding.

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Do seahorses take care of the babies after they are born?

No. Once seahorses are born, they are carried away by the ocean currents and more than likely never see their parents again. They immediately begin feeding on small plankton in the water. A seahorse may even eat it’s young if it encounters them in the aquarium.

Many fish eat their own young after they are born. Seahorses normally do not do this, however they have been known to from time to time, especially in aquarium conditions. Anecdotal evidence suggests female seahorses are more prone to this behavior than the males.

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What Do Baby Seahorses Eat?

Baby seahorses eat very small zooplankton, the small microscopic animals that drift in the ocean. Much of what they consume are copepods, very small crustaceans related to crabs and shrimp. Sheldon J. Plankton from Sponge Bob Squarepants is modeled after a copepod.

Plankton from Spongebob Squarepants.

Like the Sponge Bob character Plankton, copepods only have one eye. Unlike Plankton, they do not operate their own restaurants.

In captivity, baby seahorses can be fed a number of things. Most commonly offered is newly hatched artemia (also known as brine shrimp). However some babies are so small that they have to eat even smaller foods. In that case, the aquarist must grow their own copepods and rotifers.

You can read more about the foods they need here.

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Do seahorses mate for life?

Not really. Some species do form pair bonds that last a mating season. But only one seahorse species, White’s Seahorse Hippocampus whitei, has been found to keep pair bonds for more than a single season. However even they will find new mates when separated from their partners. Many seahorses are sort of monogamous, meaning they may stay together for a few breeding cycles, but switch mates if the opportunity arrises. On the other hand, some seahorse species are flirty little tarts, and will switch partners every time they mate.

You can read more about seahorses and the myth about mating for life in the article What’s Love Got to Do With It? The Truth About Seahorse Monogamy

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