What’s the Difference Between a Fluke and a Flounder?

One of the fun adventures my girls had on our vacation this year was going sea fishing on the commercial fishing boat Miss Avalon out of Avalon, NJ. My wife was in charge of this particular outing as I am strictly a bay fisherman – I leave the surging swells to those with cast iron stomachs.

Turns out, my wife doesn’t have one either, but that’s another story! You can read about their adventure at My Daughters’ Catch of the Day

Both the girls caught fish out on the Miss Avalon. My older daughter Nell’s fish was large enough to capture second place in the boat’s pool. First prize was cash, and Nell got a free fishing excursion to go along with her one pound sea bass.

Maddie, who was the driving force behind the deep sea fishing trip in the first place, ended up with a 3/4 pound flounder. Or was it a fluke? Either way, if you’ve never seen one up close and alive, it is a most…unfortunate-looking fish.

Early Life

Flukes and flounders are types of flatfish. That means that, while they started life swimming upright, during the larval stage, they lay on either their left or right side and the eye facing towards the bottom migrated to be top-facing.

So, some flat fish are right-side-up (their left eye migrated to the right side) and some are left-side-up, meaning that their right eye migrated to the left side. What makes a particular fish turn into a left-side or a right-side fish?

And what makes a “normal” fish evolve into a flat fish? I honestly have no idea about the former, but I’m sure the latter adaptation was for camouflage while hunting for food.

The top side of flat fish are mottled and dark, making them blend in well on the ocean bottoms. And as they are bottom dwellers, this is a very good thing as they can surprise their unsuspecting prey.

All Fluke Are Flounder but Not All Flounder Are Fluke

Generally speaking, left-side up flounder are flukes, and right-side up flounders are called flounders. That sounds easy enough to remember, but it gets worse. Flukes are also called “summer flounder,” and flounder, or right-side fish, are called “winter flounder.”

It also turns out that, of the 500 plus flatfish species, there are five species that are all called flounder. It’s good to know that there is a difference, but I would be hard pressed to taste the difference between a fluke or a flounder.

Four of the five flounder species are found in the Atlantic: summer flounder (left-side up flukes), winter flounder, southern flounder and European flounder. The fifth, the Japanese flounder, is found in the Pacific Ocean.

Unless you are studying fish biology, and I’m certainly not, I think the main thing to remember is that all flukes are flounders but not all flounders are flukes. And all flounder is tasty.

Fluke & Flounder Fun Facts

I did find out some kind of fun facts about flounder and fluke, though, no matter what name you call them. Because they are so flat, large flounder and fluke (at least 8-10 pounds) are sometimes referred to as doormats or snow shoes. Finally, something about these fish that actually makes sense!

Another fun fact is that summer flounder and winter flounder are aptly named. Summer flounder (fluke) winter off of the continental shelf and only come into the bay (to be caught) in the summer.

Winter flounder come into the bay in the fall and stay through the winter until the spring. Sounds to me like fluke and flounder don’t like to stay around each other very much. It could be because fluke have teeth and winter flounder don’t, but don’t quote me on that.

As to the kind of weird names: I usually think of a fluke as a freak occurrence and flounder as a verb meaning wobbling about without a way to steer. One of the possible root words of fluke is the old German word flah, meaning flat.

I’m still not sure how something flat can also be a freak occurrence, but I don’t guess it’s every day that a fish’s eyes migrate from one side of its head to the other.

As to the name flounder, it comes from the Dutch word flodderen, which means “to flop about.” Using that definition, all fish pretty much flounder when caught, but flounders can flop about on the bottom of the ocean, kicking up sand to cover themselves, kind of like how rays do. Also, because they swim sideways, it can look like they don’t have a very good way to steer themselves.

No matter how they look or swim, they are very tasty when simply cooked. Here’s a recipe for broiled flounder in lemon butter and be sure to check out Pan Fried Flounder with Potatoes and Parsley. This is how my mom prepared fresh flounder for us as kids.