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When envisioning fish, our minds often conjure up images of familiar species like tuna, carp, or even sharks. However, amidst the vast array of marine life, there exists a creature that defies conventional expectations, the seahorse, which is actually a type of fish.
With its whimsical appearance, resembling a miniature swimming horse, the seahorse stands out as a truly unique marine creature. From their enchanting courtship rituals to their peculiar methods of swimming, to the diverse species that inhabit our oceans, there is much to discover about the seahorse.
Join us as we explore the captivating world of seahorses, uncovering their intriguing behaviors, remarkable adaptations, the diverse array of species that exist, and the challenges they face in their delicate marine ecosystems.
What is a Seahorse?
It would be very easy to get confused over what a seahorse is. Its name alone is enough to confuse you and then you learn that it’s part of the hippocampus genus which literally translates to mean horse monster. But despite this, these creatures are actually a type of fish. The seahorse is a vertebrate and depending on the species could be as small as a single grain of rice, while others may grow up to 12 inches (30 cm).
As things stand, we are currently aware of 47 species of seahorses, but scientists are continually discovering new ones. And since the ocean is so vast and largely unexplored, there could be many more lurking out there, especially when you consider that up to 14 species have been discovered in the last eight years alone.
One thing that all seahorse species have in common is their long snout, which is part of what gives them their distinct appearance. This snout is used to suck up food from nooks and crannies and can even get bigger to allow the fish to eat larger food items. Hunting for food is easy if you’re a seahorse since they have such amazing eyesight. The eyes, on either side of the head, are able to move independently of one another which means the animal can look in two directions at once.
And rather than having scales, like other fish, seahorses are covered in bony plates; this odd appearance is thought to be down to the seahorse’s genome. Other things that may kid you into thinking that they aren’t fish are the lack of caudal fins and their long, snakelike tails. You could also be forgiven for thinking that they’d find it hard to swim, but thanks to a swim bladder, they’re far more buoyant. I’ll go into more detail on how these ocean critters swim in the upcoming section.
On the sides of their head, seahorses have gills which are how they breathe. Much like many other species of fish, these gills are used to extract oxygen from the water.
How do Seahorses Swim?
Seahorses are among some of the worst fish in the ocean for swimming and they’re also the slowest moving. While their swim bladder allows them to remain buoyant, they have to work their fins incredibly hard to keep moving. In fact, seahorses must move their dorsal fins more than 50 times a second to propel themselves.
In addition to the dorsal fin, seahorses have a pair of fins located on the head; one on either side. There is also a secondary fin on the belly, but this is used to stabilize the animal as opposed to helping it move. That fast-beating dorsal fin is what moves the fish upwards while the two on the sides help with direction which makes them very maneuverable, even if they’re not that fast.
Their prehensile tails are square shaped and they use these to hold onto things. In some cases, a single seahorse may cling onto a coral reef for days at a time. When they’re moving, the design of their tail is thought to limit torsion damage.
Habitat & Range
Seahorses are found all over the world, and depending on the species, you may see them in both tropical and temperate waters, between 45°S and 45°N. Typically, they prefer shallow waters and can be found in one of three habitats, including coral reefs, mangroves, and seagrass beds.
Since seahorses are not fast swimmers and have a range of predators including fish, crabs, rays, and sharks, they need to conceal themselves within their habitat. It’s fortunate then that they are masters of disguise and are able to camouflage themselves thanks to their appearance.
For example, some species, like the spiny seahorse, have spines that look strikingly similar to local sea vegetation, allowing them to hide in plants. In some cases, seahorses can grow new filaments on their bodies to better help them blend in. Moreover, these amazing animals have cells called chromatophores which allow them to alter their color to blend into the background.
The primary food source for seahorses is crustaceans. This includes things such as mysid shrimp, which the seahorse sucks up from the seafloor or those that are floating in the water. They use their snouts for feeding and are notoriously slow eaters, largely due to their very primal digestive systems that lack a stomach.
Seahorses also do not have teeth and since their food moves through their bodies so quickly, they spend the majority of their day feeding. Over the course of a single day, one seahorse could eat as many as 3000 brine shrimp.
While seahorses do mainly feed on crustaceans, some have been observed eating small fish and a variety of invertebrates.
There’s potentially nothing quite as odd as seahorse reproduction. Males are continuously pregnant and in a single birth, there could be as many as 1500 babies!
It was previously believed that seahorses mate for life. However, while there is a degree of pair bonding, it’s not necessarily lifelong. Instead, a couple will stay together for the entire breeding season, meeting early in the morning to strengthen their bond. In fact, research has shown that females actually go off their partners if they are separated from them for a long time.
It’s at this time that the male will engage in a very unique courtship ritual in which he performs a dance, spiraling around an object and even changing color. Males and females occupy different territories, with the female territory being much larger, up to 1,076 square feet (100 square meters). Once the courtship display is over, the female will return back to their own territory.
One of the most unique things about the seahorse is it’s actually the males that carry the young, and they do this in a pouch on the front side of the tail. However, females still produce eggs, it’s just that they will deposit these in the male’s pouch where he will fertilize and carry them.
When the time comes to give birth – usually between 9 and 45 days after fertilization, the males will release the young with the help of contractions, but this process could take up to 12 hours.
Depending on the species of seahorse, there could be as many as 1500 young in each birth and these are known as seahorse fry. However, smaller species may only produce between 50 and 150 young at any one time. Shockingly, only as few as 0.5% of all fry will make it to adulthood.
But once the young have been born, it’s not uncommon for the male to breed immediately after throughout the duration of the breeding season.
Types of Seahorses
With 47 species of seahorse discovered so far and more being discovered all the time, the diversity is pretty impressive. With that in mind, let me introduce you to some of the most interesting seahorse species on the planet.
1. Pygmy Seahorse (Hippocampus bargibanti)
The pygmy seahorse is the smallest known species of seahorse and measures just 0.79 inches (2 cm) at its biggest. They live in coral reefs in the Indo-Pacific region and are sometimes called the Bargibant’s seahorse. That said, you’d have a hard time spotting one as these are some of the most well camouflaged seahorses out there and it was this disguise that meant it was undiscovered by humans until 1969.
Pygmy seahorses feed exclusively on gorgonian corals, and the rounded tubercles on its body resemble this coral perfectly. They use their curly tails to cling onto the coral, and these seahorses can either be gray with pink or reddish tubercles or yellow with orange tubercles.
Like most other species of seahorse, it is the male that carries the young, but unlike other species, the courtship rituals do not last as long owing to fewer numbers and a greater need to mate quickly. Unfortunately, as of 2016, the pygmy seahorse has been listed as threatened on the IUCN Red List.
2. Zebra Seahorse (Hippocampus zebra)
With a striking black body with off-white markings, it’s not hard to see where the zebra seahorse got its name. These are mid-sized seahorses that may grow up to 3.1 inches (8 cm) in length and are popular pets in the marine trade. However, they are considered to be threatened.
Native to the northern coasts of Australia, the zebra seahorse feeds mainly on shrimp, and adults may feed up to 50 times a day. But if you thought that was a lot, consider that the fry may have up to 3000 separate meals each day!
Zebra seahorses live around coral reefs and aren’t typically found at depths greater than 226 feet (69 meters). In order to communicate with one another, zebra seahorses make sounds that are similar to smacking your lips!
3. Dwarf Seahorse (Hippocampus zosterae)
As you may guess from its name, the dwarf seahorse is a small species that doesn’t usually grow to more than 0.98 inches (2.5 cm), although some larger individuals have grown to double this. These are the slowest moving seahorses that only cover around 5 feet (1.5 meters) in an hour.
While they may not be able to get away from predators very quickly, dwarf seahorses are wonderful at camouflage thanks to cirri that look like algae, allowing them to hide out in marine vegetation.
You’ll find dwarf seahorses in the Caribbean Sea as well as parts of the western Atlantic Ocean. They can be a variety of colors including brown, yellow, green, and tan. They prefer habitats with lots of seagrass and live in shallow waters where they’ll hunt for small fish and crustaceans.
4. Lined Seahorse (Hippocampus erectus)
Lined seahorses are found in mangroves and, just like other species, are very poor swimmers. In order to protect themselves, they rely on their color and texture to hide from predators among the seagrass.
These are some of the bigger seahorses in our oceans that can get as large as 7 inches (18 cm) in length. What’s more, some of them will live for as long as four years. Sadly, in recent assessments, they are now considered to be a vulnerable species. But that isn’t to say that they don’t have a wide distribution, with lined seahorses being found as far north as Nova Scotia and as far south as several South American nations and even the Azores.
What’s interesting about the lined seahorse is that it will change its color in accordance with its mood. However, other factors can affect its color including diet, stress, and changes to the environment.
5. Spiny Seahorse (Hippocampus histrix)
The spiny seahorse is one of the best seahorses when it comes to camouflage as its spiny cirri allow it to blend in perfectly with vegetation. Despite its ability to hide from predators, numbers are in decline and the spiny seahorse is now listed by IUCN as vulnerable.
These seahorses use their tails to cling onto seagrass, where they’ll float in the water, becoming almost indistinguishable from their surroundings. While here, these animals wait patiently for passing crustaceans which they suck up with their long snouts.
They’re only found in Indo-Pacific regions, and have a particularly long snout and can grow up to 6.7 inches (17 cm) in length.
6. Big-Belly Seahorse (Hippocampus abdominalis)
Where the tiny pygmy seahorse is the smallest species, the big-belly seahorse lays claim to being the largest. These seahorses can grow up to 14 inches (35 cm) in length, and the males have a very prominent belly, which is where they get their name. However, this is not a trait we see in females.
Big-belly seahorses often have filaments on their heads and bodies and can come in a variety of colors, including brown, orange, or even mottled. They’re found in the waters around Australia and New Zealand, where they live among seagrasses and around rocky reefs.
Much like other species of seahorse, the big-belly seahorse feeds mainly on crustaceans and will grip onto seaweed with its long tail as it waits for its prey to pass by.
7. Tiger Tail Seahorse (Hippocampus comes)
The tiger tail seahorse is a vulnerable species that is native to oceans around India, Thailand, Malaysia, and other Asian countries in this region. What’s very interesting about this species is how it communicates. While many species will emit a series of clicks, the tiger-tail seahorse can also produce growls and purrs, which are thought to be used in various types of communication.
During the breeding season, females can deposit as many as 2000 eggs in the male’s pouch which he will carry for anywhere up to four weeks. However, it’s usually only between 200 and 600 eggs that will actually spawn.
The main cause of concern for these endangered seahorse is habitat loss and they usually live in coral reefs. They’ll feed on a diet that’s very similar to other species including shrimp and plankton.
8. Yellow Seahorse (Hippocampus kuda)
Found in Indo-pacific regions, more than 23 countries have confirmed the presence of the yellow seahorse in their waters. These seahorses grow larger than many others, reaching around 12 inches (30 cm), although 7 inches (17 cm) is also considered to be within the average range.
They inhabit shallow waters such as harbors and lagoons and while you may spot them here, they are considered to be vulnerable on the IUCN Red List. Despite this, they are still a very popular choice for marine aquarium owners.
Unlike species like the spiny seahorse, the yellow seahorse has no prominent spines but instead has a series of smooth bumps over its body. The coloration can range from yellow to cream with dark markings.
9. Pacific Seahorse (Hippocampus ingens)
It won’t require a second guess from you to understand that the Pacific seahorse can be found in the Pacific Ocean. It’s most common from Chile in the south up to Baja, California in the north and can be found among seagrasses, on rocky reefs and even in mangroves.
These are nocturnal seahorses that use camouflage to protect themselves from predators. They’re mid-range in terms of size, typically growing to around 7 inches (19 cm) although there are some individuals that have been reported to have gotten as large as 12 inches (30 cm).
The Pacific seahorse, sometimes called the giant seahorse, ambushes its prey which can include things like shrimp and plankton. They are considered to be a vulnerable species, although individuals can live up to five years in the wild.
10. Knysna Seahorse (Hippocampus capensis)
Sometimes called the cape seahorse, the knysna seahorse is endemic to the southern coast of South Africa. It’s considered a national treasure in this country and is one of only two seahorse species that is listed as endangered. Since the body of water that it inhabits is so heavily used by humans, this has led to a decline in the quality of its habitat.
Knysna seahorses are the only known species of estuarine seahorse, and it’s believed to have been around for more than 40 million years. Unlike other seahorse species, it can live in waters with salinity as low as 1%.
These seahorses grow to around 5 inches (12 cm) in length, and the coloration of each individual is unique since it is affected by the environment, as well as the seahorse’s mood.
11. Short-Snout Seahorse (Hippocampus hippocampus)
Short-snouted seahorses are commonly found in the waters of the North Atlantic. However, back in the mid-2000s, colonies were discovered inland, in London’s River Thames. They prefer shallow waters, particularly muddy areas where there is a lot of seagrass.
This species is listed on the IUCN Red List as being data deficient meaning that we cannot get a clear picture of its conservation status. That said, in the United Kingdom, the species is protected. Here, there are annual breedings at London Zoo, and in 2010, as many as 918 babies were born here.
Short-snouted seahorses are mid-sized seahorses that can grow up to 6 inches (15 cm) in length. As their name suggests, the snout is incredibly short, as well as being slightly upturned. They use their snouts for feeding and can eat up to 50 shrimp every day.
12. Long-Snouted Seahorse (Hippocampus guttulatus)
The long-snouted seahorse grows to around 6 inches (15 cm) in length and can be found in waters around the coast of Great Britain. However, it is also common as far down as the Mediterranean Sea, the Canary Islands, and off the coasts of Morocco.
Long-snouted seahorses have, as you can imagine, long snouts and long, thin tails. They are often brown to yellow in color and have long, slender bodies. When the males give birth, as many as 1000 to 1500 fry are released into the water.
In the UK, these seahorses are often referred to as the spring seahorse, but they are not the same as the spiny seahorse I discussed earlier in this guide from the Indo-Pacific area. These seahorses, much like other species, feed on small crustaceans and prefer to live in shallow waters, not typically any deeper than 66 feet (20 meters).
13. Barbour’s Seahorse (Hippocampus barbouri)
If there’s any type of seahorse that likes to stay in shallow waters, it’s the barbour’s seahorse which is not usually found at depths greater than 33 feet (10 meters). These seahorses frequent the coastlines of countries like the Philippines and Malaysia and enjoy a habitat with lots of seagrass.
Like many other seahorse species, the Barbour’s seahorse is listed as vulnerable and has been since 2017.
This is a very spiny species of seahorse with a long slender snout. Over the body and tail, you will notice spines that are both long and short in length as well as four to five spines on the crown. They typically grow to around 6 inches (15 cm), however, the females tend to be slightly smaller at around 5 inches (13 cm).
14. Giraffe Seahorse (Hippocampus camelopardalis)
The giraffe seahorse is a species that is found in the east and southern waters surrounding Africa. It’s a small to mid-sized species that generally grows to around 4 inches (10 cm) in length, and lives quite deep down, up to around 148 feet (45 meters). Their preferred habitats are areas where algae is plentiful where it feeds on small crustaceans. However, not much is currently known about this species.
Sadly, the giraffe seahorse is under threat. While it is classed as data deficient on the IUCN Red List, we do know that it is often targeted in Chinese medicine. But the biggest threat to this species is fisheries in Mozambique, whose nets are dragging up unnecessary numbers of giraffe seahorses.
15. Japanese Seahorse (Hippocampus mohnikei)
The Japanese seahorse is a beautiful species with distinct markings and spines. They only grow to around 3 inches (8 cm) in length and are found around the coastlines of East Asia. As you may guess from the name, this species is commonly found around Japan, and it was thought, for many years, that it was endemic to the area. However, we are now spotting these seahorses around the coasts of India and Cambodia.
Japanese seahorses are, as many other species, considered to be vulnerable on the IUCN Red List. They’re typically found at depths no greater than 33 feet (10 meters) and prefer coral reefs and seagrass habitats.
For the first six months of their lives, Japanese seahorses are in a plankton stage and will drift along the current with other species of plankton before growing as their food sources change.
16. Slender Seahorse (Hippocampus reidi)
Sometimes called the long snout seahorse, the slender seahorse is a subtropical species that is found around the coasts of southern North America, Central America, the Caribbean, and South American countries such as Brazil and Columbia.
These seahorses are often found around coral reefs but may also frequent seagrasses and mangroves. While smaller individuals remain in shallow waters, some larger slender seahorses can be found at depths of up to 180 feet (55 meters).
Unfortunately, this is a target species for the Chinese medicine industry, and as many as 25 million seahorses, including slender seahorses are caught and traded in Brazil each year. As a result of this, the species is now listed as near threatened.
Threats Faced by Seahorses
While there are lots of species of seahorses, many of these are now considered to be vulnerable, according to the IUCN. Some of the most threatened species include the cape seahorse owing to its very limited geographical range. But this isn’t the only thing that threatens these wonderful creatures.
Pollution is a very significant threat to seahorse populations, with things like oil spills being so significant that one such event threatens to entirely wipe out the smallest species of seahorse. Even the clean-up operation could pose a risk, but this isn’t the only problem where pollution is concerned.
Think about all of the chemicals that humans use for things like farming; these runoff and end up in our oceans where they’re doing great harm to marine life, including seahorses. In some parts of the world, raw sewage is being pumped straight into the ocean which upsets the nutrient balance.
Other items are being dumped into the ocean and these can seriously affect wildlife which may become trapped among them. For example, one shocking photograph was taken of a seahorse that had gotten caught up in a face mask disposed of in the ocean.
While not all fishing attempts target seahorses, they’re often caught in the crossfire of non-selective fishing nets and become what is known as bycatch. In one study, it was noted that as many as 37 million seahorses were accidentally caught and this wasn’t even information from every country in the world, so numbers are likely much greater.
While most fishing around the world is closely regulated, there is still a lot of illegal activity. While seahorses are commonly used in Chinese medicine, many countries have now banned the fishing of them including Thailand and Vietnam.
It’s thought that capturing seahorses for use in Chinese medicine could be one of the reasons that we have seen a decline in several species by as much as 70% in recent decades. While there’s no scientific evidence to suggest that these medicines even work, experts claim that, if there were, we still should not fish for seahorses and look at other ways to mimic their properties.
It’s believed in traditional Chinese medicine that seahorses can cure things like incontinence, asthma, skin complaints, and much more. They’ve been used this way for more than 600 years, and in many cases, the seahorses are eaten as a tonic.
Habitat loss is a problem for many creatures on both land and in the sea, and seahorses are no exception. In many areas, the waterways are so heavily used that this directly impacts the quality of the seahorses’ habitat.
What’s more, since bottom trawling is a popular method of fishing, this is a serious problem that ruins swathes of ocean habitats where seahorses dwell. When using this method, many seahorses are caught in the nets.
Souvenir & Aquarium Trade
If you head to certain parts of the world, you’ll notice stalls and stores selling dried seahorses and other knick knacks, which have caused the death of millions of these innocent creatures. This problem is most prominent in places like South Asia and West Africa, where trades take as many as 37 million seahorses every year.
On top of this, seahorses have become a popular choice as a pet in marine aquariums. What’s most worrying about this is that the seahorses are often taken as juveniles from the wild, which means they have not yet had a chance to breed; this significantly reduces wild populations.