Is Seahorse a Fish or Mammal?

A seahorse is a fish and belongs to the class Actinopterygii. Besides, seahorses have swim bladders to remain floating on water. They respond through gills like all other fishes and lay eggs to produce offspring. However, seahorses don’t have fins like regular fish. Instead, they have snake-like tails.

Is Seahorse a fish or mammal? Well, this is one of the most commonly asked questions about this tiny little marine species. No matter how often we tell people this, they really don’t want to accept seahorses as fish. Well, people aren’t wrong. There are many reasons not to consider seahorses a fish, which is understandable.

But there are plenty of common traits between a fish and a seahorse, proving that seahorses are fishes. Well, if you’re still not clear and can’t connect the dots, don’t worry, we’ve got your back! We’ve made this guide to help you clear your misconceptions and provide a detailed compare-contrast between seahorses and fish.

Is Seahorse a Fish?

Both seahorses and fishes have plenty of common traits and characteristics between them. But the unusual shape of seahorses, the shape of their head (like a horse), and their snake-like tail often create misconceptions. As a result, people think they are not fish.

Today, we’re going to dive deep into the fact and make a comparison between regular seahorses and fish and find out whether seahorses are fish or not!

Seahorses have unique body structures or shapes. They’re identified primarily with their horse-head-shaped head and dragon-like tail. Besides, they’ve no scales on their body and cannot withstand heavy currents.

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On the other hand, a normal fish has scales, fins and a good swimmer even in heavy currents.

So the question is, even with so many differences and contrasts, how Seahorse is a fish?

To help you with that, a chart is provided below with the common traits of a fish and a seahorse and you’ll know why seahorse is a fish-

Family and Class  Seahorses fall in the Family of Syngnathidae. Pipefish and sea dragons are also included in this family. The nearest relatives of seahorses are trumpetfish and coronet fish. Besides, seahorses fall under the class Actinopterygii. Alongside seahorses, all other bony fishes like Salmon or Tuna are also a part of this class.  
Habitat  Seahorses are marine animals. That means they’re found in different types of water depending on their type and structure. Well, this is quite the same for regular fish too.   Moreover, seahorses are found in shallow weedy areas. They do this to avoid predators and heavy currents. Like seahorses, many fishes can be found in shallow water and around weedy areas.  
Respiration  Like any other fish, seahorses are found in water, and their mode of respiration is gills. Seahorses breathe through gills and have a swim bladder (gas-filled organ) that helps them maintain buoyancy and swim underwater.  
Body Structure  Seahorses have exoskeletons and don’t have any visible scales. However, the exoskeletons are a form of dermal scales and act as fins. They have external hard bony plates that are covered with a fleshy layer. Like seahorses, some fishes also have an exoskeleton and dermal scales. So indeed, a Seahorse is a fish!  
Reproduction  Like all other fishes, seahorses lay eggs to give birth to their babies. They carry the eggs in their pouch, and the eggs are released once they are fully developed. Although seahorses lay eggs like fish, there’s a catch. Normally in seahorses or sea dragons, male seahorses carry those eggs until they’re fertilized. The female seahorses lay the eggs in the male’s pouch, and since then, the male carries the eggs. This is one of the differentiating factors between a fish and a seahorse. However, as the mode of reproduction is the same (by laying eggs), seahorses can be termed as a fish.  
Food Habit  Seahorses and regular fish feed on plankton and small fishes on a regular basis. The main food of seahorses is plankton, small fishes, and crustaceans like shrimp. As they’ve no stomach, they eat all the time. Due to their tiny size compared to fishes, seahorses live on tiny animals and plants.
PetsWe all have heard about keeping fish in aquariums as pets. But what if I tell you seahorses can also be kept in an aquarium? Surprised, right? Well, seahorses can be kept in the aquarium just like other fishes. Seahorses are exported to different countries of the world, and if you’re lucky, you might find one in your nearest local market. Although seahorses and fish can be kept in aquariums, the requirements differ. Seahorses prefer a colder temperature and more salinity compared to regular fishes. So yes, they can be kept in aquariums, but keeping them is a big challenge as their survival chances are low compared to fish.  
Average Lifespan  The average lifespan of a fish and a seahorse is quite similar. Both seahorses and fish live around 3 to 5 years on average. But there are long-living fishes, like goldfish, that live up to even 20 years!  
Seahorse anatomy
Anatomy of a seahorse

Is a seahorse a fish or mammal? Well, I believe you’ve got your answer. So next time anybody says seahorses are mammals and not fish, you know how to enlighten them, right?

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Why Do People Think Seahorses Are Not Fish?

Reading this far, I believe you’ve learned why a seahorse is called a fish. However, there arises another question. Why do some people still have doubts even with all the similar characteristics and everything?

Well, the answer is- although seahorses and fishes have many major and common characteristics, some characteristics do not match fully.

  • The main differentiating factor is the body structure. Seahorses have unique and abnormal body structures compared to fish. The horse-like head and dragon-like tail simply differentiate them from regular fishes.
  • Unlike fishes, seahorses are terrible swimmers. On top of that, they cannot withstand heavy currents. This is one of the factors why people don’t consider them as fishes.
  •  Seahorses have no stomachs. That means they cannot store food. For this reason, seahorses eat all the time of the day. And it’s definitely a major differentiating factor.
  • Although the mode of reproduction is similar between a fish and a seahorse, in seahorses, males carry the eggs until they’re fertilised. This is very abnormal compared to any living animal.


Seahorses are fishes with many common traits and characteristics. Yes, I agree that some characteristics don’t match, but don’t all animals have some unique characteristics that differ from others?

So, Is a seahorse a fish? I believe you know now and have cleared your queries and confusion.

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