Flounder Identification 

“Flounders” actually refers to a group of various species, some of which aren’t related all that closely.  Gulf, southern, summer flounder (fluke), and winter flounder are some well-known examples, but this group can also include the halibut.  

Summer and winter flounder are very commonly fished—and commonly confused with halibut.  This is due to similar body shapes, coloring, and eye positions.  Although the halibut is a type of flounder, most anglers use “flounder” to refer to the winter or summer species.  

To identify flounder vs. halibut, you can look at its size first and foremost. Flounder don't grow nearly as large as most halibut, so the smaller your catch, the more likely it's a flounder. 

Body and tail shape are another difference. Flounders have rounded dorsal and tail fins, and a rounder body overall.  Halibut are longer and kind of diamond-shaped by comparison.  

Another helpful clue can be the direction of the eyes.  Although both halibut and flounder experience eye migration during metamorphosis, flounder have this happen to either side, depending on the species.  Summer flounder or flukes will have their eyes on the left, and winter flounder will have them on the right.  Halibut are almost always right-facing, so you can easily distinguish it from a fluke by its eye direction alone.  

The size of your fish’s mouth is another indicator of what you’ve caught.  Flounder have smaller mouths and visible teeth, unlike halibut.  

See related article: Fluke Vs Flounder

Halibut Identification 

Halibut are flatfish and included in the flounders' family.  Like summer or winter flounders, they're bottom-feeders (also known as demersal fish) but will swim off the bottom to feed when food is scarce.  By contrast, flounders tend to stay at the bottom almost all the time.  

Halibut have large mouths and more "hidden" teeth, shaped like cones.  They also grow bigger than other flounder species and have more of a diamond shape in both their body and dorsal fins.  The tail fin has a bit of a fork, as well, unlike the rounded tail fin of fluke or winter flounder.  

Most halibut have both eyes positioned on the right.  While it’s possible to find halibut with eyes on the left, it’s incredibly rare.  With flounder, you can find them on either side pretty equally, depending on the species.  

Size is a very useful indication you’ve caught a halibut vs. flounder.  Simply put, flounders don’t get very big.  Around five pounds is common, with the current world record for summer flounder being just over 22 pounds. Compare that to the world record for halibut—over 500 pounds—with an average weight of about 30 to 50.  

The California halibut may seem like an exception, as it typically weighs between 5 and 30 pounds.  However, it isn’t actually a halibut: just another type of flounder.  

Flounder Vs Halibut - Key Differences Compared  

1. Habitats 

Because both flounder and halibut are demersal fish (and because halibut is, technically, a type of flounder), they share similar habitat preferences. They belong to the flatfish group and thus enjoy spending most or all of their time on ocean or bay bottoms.  

One difference is that halibut will venture off the bottom to feed now and then, especially when food is scarce.  Both fish can be found along coastlines in the Atlantic or Pacific Oceans, although it’s important to note that Atlantic halibut is an endangered species.  Fishing for this species isn’t prohibited, but it is currently restricted in the United States. 

Both species migrate to deeper waters to spawn.  Pacific halibut spawn in the winter.  Summer flounder (fluke) spawn in the fall and winter, while winter flounder spawn in the later winter and springtime. Atlantic halibut have the latest spawning season: late winter to early spring in some waters.  

2. Fishing Location 

Depending on the type of flounder or halibut you’re after, you can find either fish along U.S. and Canadian coasts in the east and west. Halibut can also be found in Russian or Japanese waters, with one species—the Greenland halibut—even being found in the Arctic.  

Flounder are much more common in U.S. coastal waters. Halibut are located mostly north, in the upper region of California, Washington, and Alaska, as well as Canadian coastlines. In other words, the farther south you are in the States, the more likely it is you’ll catch a flounder vs. a halibut.  

3. When To Fish (Seasons To Catch Them) 

Both flounder and halibut can be caught year-round, but springtime is generally regarded as best.  Early to mid-summer, especially in northern areas where the water stays cooler for longer, can also be productive times to plan a fishing trip.  

Flounder are most active in the early morning or late afternoon.  High tide is an excellent time to cast since this is when they feed.  

For halibut, try slack tides—the hours just before and after high tide, but also before and after low tide. This allows you to maximize how much time your bait spends in a halibut’s strike zone, increasing your chances of a bite.  

Some anglers use the moon phases and resulting tidal patterns to determine when they should fish for halibut.  A full moon or new moon has a stronger gravitational pull, which increases the strength of the tides.  The result is more bottom contact (the optimal strike zone for a bottom-feeding fish like the halibut), which leads to frequent bites. 

4. Ease of Catching Them 

Demersal fish like flounder and halibut can be tough for beginners to catch, especially if you’ve never ocean fished along the bottom before. The most challenging part is getting—and keeping—your bait close enough to the bottom where the target fish will see it, but not so low it drags or gets swept away in the current.  

Flounder are easier to catch than halibut because they aren't as large. Also, since flounder weigh much less, beginners will have an easier time bringing their catch in.  Halibut, on the other hand, can weigh tens or hundreds of pounds and measure several feet in length—not so easy for new anglers to land.  

Beginners might enjoy learning to fish along the bottom in the ocean with flounder first, then target halibut when they’re more advanced.  

5. Which Tastes Better? 

Both halibut and flounder have a mild taste that appeals to many people, without the "fishy" flavor many of us dislike.  Texture is really where these two fish differ.  

Flounder has more fat than halibut but less meat overall.  Its fillets are flakier and thinner.  Halibut, which is quite lean, has a denser, firmer bite to it and provides much more meat per fish.  

Either fish can be grilled or baked, although the former is more popular for halibut.  Its density and low fat content make it perfect for grilling, whereas flounder is better suited for pan-frying or baking.  

6. Which Is More Nutritious? 

Halibut and flounder are both very healthy options to add to your diet, but halibut is a little more caloric.  In an 8-ounce serving of halibut, you’ll get about 300 calories, compared to 250 or so for the same amount of flounder.  

Protein content is nearly identical between the two. Both contain good sources of Omega-3s and other nutrients such as selenium, B vitamins, and magnesium, which can help reduce inflammation and oxidative stress.  

Flounder and halibut are both nutritious.  If you can eat some of each regularly, that’s ideal—and if not, opt for whichever is freshest.  This means forgoing Pacific halibut in favor of summer flounder if you live in the southern United States, for example, or choosing halibut over flounder if you live in the northwest.  The fresher a fish is, the more nutrients it will have by the time it hits your plate.  

People also Ask (FAQs)

Are halibut aggressive? 

Halibut aren’t that aggressive, but they are incredibly large and strong compared to some fish species.  The fight they put up when you hook them isn’t aggression so much as struggling. 

With that in mind, halibut are carnivorous ambush predators, which means they strike prey (including other halibut) when it swims by. Some anglers call halibut aggressive because of these powerful, sudden feeding strikes, but that’s a good thing: it means when they spot your bait, they’ll attack it quickly.  

What does the halibut eat? 

Halibut eat crustaceans, pollock, crabs, octopus—any number of sea creatures that wander past. Herring is one of the most popular baitfish for catching halibut.  

Will flounder eat chicken?  

Some anglers swear by raw chicken as bait for flounder, especially when cut into strips, so it moves with the current and catches their attention. Others stick to the classics, reasoning that it’s more effective to lure fish with what they already eat.  

Most experts agree that introducing chicken—often treated with antibiotics—into an ecosystem isn’t a good idea, however. There’s also the risk of contracting salmonella, since properly handling raw meat is difficult on a dock, shore, or boat.  

Can flounder be farm-raised? 

“Flounder farming” has been attempted several times, by both large- and small-scale operations, but is generally considered too expensive.   

What’s the biggest halibut ever caught? 

Currently, the world record for Atlantic halibut weighed 515 pounds and was caught in Norwegian waters in 2013.  For Pacific halibut, the record is 459 pounds.  It was caught in 1996 in Alaska, by Jack Tragis near Dutch Harbor.  

Why is halibut so expensive? 

The higher price point of halibut can be attributed to scarcity (there are fishing limitations on Atlantic halibut, which is endangered) and location.  The farther you are from where the halibut was caught, the more it costs to transport it.  

Conclusion

Halibut and flounder are sometimes confused, and it’s easy to understand why.  Although halibut is a type of flounder, most anglers use “flounder” to refer to the summer or winter species. The best way to tell halibut and flounder apart, besides some body shape differences, is size.  Halibut grow significantly larger than summer and winter flounder.