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!

Seahorse Facts

Are there any freshwater seahorses?

No. All seahorses are marine fish, though some tolerate brackish conditions (brackish being part way between freshwater and as salty as the ocean). Sometimes you may see a “freshwater seahorse” for sale in a fish store. These are actually pipefish, a close relative to seahorses. They don’t have the traditional horse-like body shape. They look like a stretched out fish, or even a tiny snake.

Worm Pipefish - Nerophis lumbriciformis

A tiny pipefish – Nerophis lumbriciformis – Photo by Ian Boyd

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Are seahorses happy living alone? Or are they social with each other?

Most seahorses live together as pairs in the wild. The male is the “home maker” and stays in a very small area, while the females go out and explore and have a territory up to 10 times the size of the male’s. Every morning they greet one another with a dance where the pair swim side by side, tails entwined. Then they separate until the next day, where they meet again and go through the same ritual.

In aquariums, people do tend to keep more than just two. They are generally not aggressive towards each other, though if there is a female to be fought over, the males may “tail wrestle”; grabbing on to each others and trying to force the other one away. Sometimes, they will “snick” at each other when really mad (snick being the action they take when eating, a loud click can be heard and they rapidly syphon water). Generally though, they are pretty docile.

A small number of species do live in groups in the wild as well. These do not form faithful pair bonds, and instead compete for mates every time they get ready to spawn. This is true for the Potbelly Seahorse Hippocampus abdominalis, and the Short-Headed Seahorse Hippocampus breviceps.

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How big do seahorses get?

The largest seahorse is Hippocampus abdominalis, which grows to 35cm (just under 14″).

Pot Belly Seahorse in the wild

Pot Belly Seahorse in the wild

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Where do seahorses live?

Seahorses are found in temperate, subtropical and tropical oceans around the globe. They don’t live in freshwater, though some live in river estuaries that meet the ocean where the water is partially saltly, this water is called “brackish”. They can only tolerate the salinity (or “saltiness”) of the water that is about half as salty as the ocean, any lower and they can perish.

Most seahorses live in shallow waters, under 20 meters (60 feet) but some are found at depths of over 100 meters (300 feet). It’s possible more go even deeper, as much of these deep water habitats are unexplored.

Seahorses live in a range of habitats, but tend to prefer either seagrass beds or coral reefs. Some species, such as the pygmy seahorses, live on a single coral. It’s not known if they live on one coral their whole lives, or if they stay on a single coral. Seahorses also like man-made structures, and are particular to shark nets. In Australia, divers help remove seahorses before replacing old nets to keep from disturbing them.

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How can I tell the difference between a female and a male seahorse?

Male seahorses have a pouch, while the females do not. The pouch is at the base of the tail, and slopes from the body down to the tail, so the transition is smooth. A good description I heard is if you look at the overall shape of the seahorses body and tail, males look like a D while females look like a P.  Male seahorses also have a ridge on their chest called a keel, and most males have shorter snouts than females, though the differences are subtle and can be difficult to see.

Immature seahorses look like females.

This illustration shows a male and female side-by-side:

Seahorse Anatomy Male Female

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Does water temperature effect sea horses?

Yes. Seahorses come from seas ranging from temperate (cold water) to tropical (warm water). If a species from temperate waters is exposed to excessively warm water, they become stressed, possibly to the point of being fatal. This is one reason climate change is a threat to seahorses. One additional problem is that the warming of ocean temperatures appears to be causing warm water species to invade territories they never have before, competing with the native seahorses. For instances, there is record of  Hippocampus algiricus  being found around the Canary Islands for the first time, and cross breeding with the native  Hippocampus hippocampus.

Cold water can have the same effect on tropical seahorses. Water that is too cold can stress tropical seahorses and too cold can kill them. Water that one species is perfectly happy in can be fatally too cold for other species.

In the home aquarium, temperature is also very important. Seahorses have a  primitive  immune system, which makes them very  susceptible  to bacterial diseases. In the wild, or even systems with large volumes and relatively low bioloads (the number of animals in a system), bacteria counts stay low. But in a home aquarium, bacteria tend to occur in much larger numbers. For years, people tried to understand why their seahorses were getting sick so frequently. In warmer water, bacteria reproduce at faster rates. The warmer the water, the faster bacteria reproduce. Seahorses are more prone to become ill do to overwhelming numbers of bacteria, especially when stressed, while other fish, because of their more advanced immune systems, are better equipped to deal with bacterial illness so they don’t get sick as often.

What aquarists have found is that turning the temperature down a few degrees from what they would experience in the wild. While it is only a hypothesis, the practice of keeping seahorses at temperatures slightly lower than they might be found in the wild has significantly reduced the amount of illness seahorses in captivity experience.

You can read more about temperature and seahorses in the aquarium here.

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What happens to seahorses during the winter?

It depends on where in the world you are. Near the equator, the behavior of seahorses stays the same all year long and they generally maintain the same territories. In Northern and Southern climates with a distinct seasonal change, they travel to deeper water in the winter. Not much is known about what they do in the deeper water, or how far they travel. They likely go to deeper water because the temperature stays more stable than shallow water.

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How long do sea horses live on average?

This is an interesting question. Their are currently 54 species recognized seahorse species, and their lifespan likely varies by species. For instance, dwarf seahorses (Hippocampus zosterae) are thought to only live around 18 months and 2 years. Larger seahorses have a longer life span. Most people think it’s around 5-7 years, although we’re starting to hear reports of some living longer than 10 years in captivity.

In the wild, the oldest confirmed age is five and a half years. This is difficult to track because there are no outward indication of age once they reach maturity. The one that was confirmed to be five and a half years old was tagged and tracked over several years, so researchers were able to confirm her age. You can read more about Grandma here.

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What do seahorses eat?

Seahorses eat small invertebrates and fish. Their diet largely consists of small crustaceans. Crustaceans are the group of animals lobsters and crabs come from. In the case of seahorses though, the food they eat is much smaller. Mysis shrimp, amphipods, and crustacean larvae from larger crustaceans make up a large part of their diet – they usually eat any  crustacean between 1/2″ and 1″.  They will also eat small fish if they get the chance.

As babies, seahorses eat even smaller foods. A good portion of their diet as babies is made up of copepods. Copepods are tiny crustaceans that are about the size of a period in this sentence. Pygmy seahorses are thought to eat the same thing as baby seahorses – very tiny crustaceans.

In captivity, they are often trained to eat frozen mysis shrimp as adults.

Copepod species Euterpina acutifrons

Copepod as viewed under a microscope.

Hemimysis anomala - Bloody Red Mysis Shrimp

A single Mysis shrimp about 1/4″ long.

Amphipod

Close up of an amphipod.

If you are interested in learning more about what seahorses eat, here are a few articles that may interest you:

Seahorse and Pipefish Foods
Foods for Breeding Syngnathids

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What is a “snick”?

A “snick” is the colloquial term for the feeding action seahorses and some of their relatives make. It is a loud popping sound created by bones in the head of seahorse as they strike at prey. It has a vague “snick” sound, and so the term has been popularized to describe how they feed.

The video below shows the snicking behavior of several pipefish and seahorses:

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