While these fish have similar names, they are quite different from one another. The sunfish is the larger of the two, weighing up to 2,000 pounds and growing to be as long as 12 feet, while the moonfish is much smaller, only growing to be around 220 pounds and three feet long. 

MoonfishOcean sunfish side
Moonfish (left) vs Sunfish (right)


Key Differences between a Moonfish and a Sunfish 

  • Size: The moonfish is far smaller than the sunfish, less than half its size. The sunfish can reach up to 2,200 pounds and is 12 feet in length. 
  • Diet: the two fish share a similar diet, preferring to feed on small fish and squid. 
  • Habitat: the two fish are widely distributed, with both spending time closer to the surface of the ocean and deep within the water’s depths. 
  • Appearance: Both fish are unusual looking with distinctive fins and shapes. The sunfish has a very large dorsal fin that has been compared to the moonfish’s fins. 

We’ll explore these differences and exciting facts about these ocean creatures below.


What is a Moonfish? 

The moonfish, also known as an Opah and sunfish, is a member of the Lampridae family. There are six living species of moonfish that are usually recognized by science. There are also at least two extinct species. 


Appearance 

Moonfish are relatively small disc-shaped fish with deep orange coloring around their fins and shades of orange and brown on their bodies. They are also usually covered in white spots. The body is covered in scales that reflect a silvery color. They have large pelvic fins with around 15 rays. 

Moonfish have a pointed snout and a small toothless mouth. Most only reach around 3 feet long and weigh around 220 pounds. But, the larger species can be more than double that, up to 600 pounds.

Fisherman and Moonfish
A moonfish with its distinctive shape

Diet 

The moonfish is predatory. It lives on a diet of small fish, cuttlefish, krill, squid, and more. Its prey is usually smaller than it is, which comes from necessity since its mouths are so small. 

Habitat 

Moonfish live throughout the Northern Hemisphere but are most commonly found in the Atlantic Ocean. They live in the open ocean, meaning away from shores, and usually between 150 and 1,500 feet beneath the surface. 

These fish have been known to migrate up to warmer waters at night or during particularly cold seasons. They’re also thought to migrate deeper in order to hunt. 

Another interesting fact about the moonfish is that it is the only known fish to exhibit something called whole-body endothermy. This occurs when the fish’s internal organs are kept at a relatively consistent, higher temperature than the surrounding water. Usually, their organs are around 5°C warmer than their habitat. 

Interestingly, they also exhibit partial body endothermy in which the fish has a higher temperature around its brain and eyes than the rest of its body.

What is a Sunfish? 

The sunfish, or ocean sunfish, is the largest bony fish in the world’s oceans. It can weigh up to 2,200 pounds (far larger than the moonfish) and grow to lengths of up to 12 feet. The fish is distinguished by its long pectoral fins and tail fin.

Ocean sunfish swimming

They take their name from their habitat of spending time in the sun near the ocean’s surface. Scientists believe this is done to regulate their body temperature as they often spend time diving deep below the ocean’s surface. 

Appearance 

Sunfish
A sunfish with its distinctive shape

Credit: Opencage, CC ASA 2.5

Sunfish are large, oval-shaped fish that, in some ways, resemble disc-like moonfish. They have long dorsal and anal fins but lack a tail fin. The fish have small mouths, as moonfish do, but they do have teeth (something the moonfish lack). 

Their skin is covered in dermal denticles, something that is seen more commonly with sharks and rays. 

Diet 

Sunfish live on a diet that’s quite similar to that of moonfish. They both feed on squid and small fish. Sunfish are also known to eat sea jellies and salps. 

Habitat 

Sunfish are found around the world in tropical and temperate oceans. They live along the east coast of North America all the way to Newfoundland. But are more common closer to the equator. 

Ocean sunfish side on
Ocean sunfish side on

They are pelagic, meaning they prefer to live in the open ocean (as moonfish do). 

These fish have been known to dive as deep as 2,000 feet below the water’s surface and travel close to 20 miles a day. 

Threats 

Sunfish are so large that they have few natural predators. But sharks, orcas, and sea lions have been known to hunt them. They are also impacted by human-caused climate change and hunting. In some places, such as Japan and Korea, sunfish are considered a delicacy. 

FAQs 

Is sunfish the same as moonfish?

No, sunfish and moonfish are two different types of fish. Sunfish are far larger (they’re the largest species of bony fish!), and moonfish is significantly smaller and lighter. 

Why is a moonfish called a moonfish?

It’s believed that Opah, or moonfish, take their name from their share. They are round and can be silver in color, like the moon. 

Can you eat moonfish?

Yes, moonfish are edible and are consumed in some parts of the world. They’re considered a delicacy in Korea and Japan, among other countries. 

What fish is bigger than a sunfish?

Sunfish are outmatched by some sharks. Some shark species are far larger than sunfish, while others are smaller. 

Where do moonfish live?

Moonfish live throughout the Northern Hemisphere. It’s not unusual to find them in the Atlantic and Pacific oceans.