How to Fillet a Fin Fish

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Fish fillets before trimming. [Photographs: Vicky Wasik]

The best—and honestly only—way to get good at most things is to do them over, and over, and over. Then do them again. And again. That's an advantage restaurant cooks have over home cooks. In a single night, a line cook can fire off as many steaks or roast chickens or pastas as others make in a year. It's one of the things I loved most about my time working in restaurants, when I could obsess for weeks on end about pan roasting a fish fillet or poaching eggs until I had perfected it.

Sadly for me, in every restaurant I worked, we always had a prep cook who did most of the fish butchery, which meant I'd only have a chance to fillet a big batch of whole fish when that guy was out. I got proficient at it, but not masterful. Can I fillet a fish? Yes. Can I plow through twenty of them in less than a minute each and never so much as nick a fillet or lose a scrap to the bones? Nope. I wish I could, but those are the breaks.

But while it would be nice to have virtuosic fish butchery skills, it's not a requirement for the home cook, and it shouldn't stop you from trying your hand at it from time to time. After all, at home we're not working under the time pressures of a restaurant kitchen. We can take as long as we need to do it right.

Why do it? I'd be lying if I said it's an absolutely necessary kitchen skill, but it's useful to know how to break down a fish (in this case, I'm showing how to work with fin fish—flat fish like flounder, sole, and halibut are different). First, buying the fish whole means you can better judge the quality of what you get. Second, you can keep the bones and use them to make fish stock. And third, it's usually cheaper, even after you've accounted for the bone weight.

Sure, you could ask the fishmonger to do it all for you, but what's the fun in that? You gotta start your repetitive practice somewhere.

Judging Fish Quality

One of the advantages of working with whole fish is that you're able to really see how fresh the fish is—if you know what signs to look for. And you really should look, because there's lots of not-great fish out there. In fact, while shopping for the fish in this story, I made the mistake of not paying enough attention and ended up with a rank fish on my hands.

I was at the fish counter, and asked for two whole snapper. The person behind the counter asked which ones I wanted. I pointed to a snapper that had fairly clear eyes and looked plump and fresh. She grabbed it, then quickly grabbed a second snapper that was hidden under ice right next to it. I didn't get a good look at that second fish, but I should have, because when I got back to the Serious Eats test kitchen, I realized that it was well on its way out.

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A poor quality fish, at left, has cloudy eyes and sunken looking flesh. A better fish, at right, has clear eyes and plump flesh.

The good news is I can turn that lemon into lemonade by using it as a teaching moment here. The bad fish showed every textbook sign of deterioration. Here they are, along with what you should look for instead:

  • The bad fish had a terrible fishy odor that immediately made me cringe. A good fish will smell like a fish, but it should be a clean, fresh scent...sometimes I even think a pristine fresh fish has a whiff of cucumber to it.
  • The bad fish had eyes that were clouded over. A fresh fish will have clear, plump eyes.
  • The bad fish had a sunken look to its flesh, and felt almost mushy under the skin; when pressed on a meaty part, it left a deep indentation behind. A good fresh fish is plump, bordering on firm; press on it, and the flesh shows some resilience, bouncing back and leaving less of a dent.

Insist on being able to smell and examine your fish before buying it. Otherwise you'll have to make a return trip to the fishmonger to get your money back, just like I did.

Filleting The Fish

Tools

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The best knife for filleting fish is a filleting knife, which is recognizable by its long, thin, and flexible blade. The flexibility of the blade is helpful, since it allows you to press down against the bones as you work and it will conform to their contours better than a rigid knife would. Its thinness, meanwhile, reduces friction as the knife slides between meat and bones. Can you use a different knife? Yes, but it'll be more difficult.

I'd recommend just picking up an inexpensive filleting knife, like the Dexter-Russell one I'm using here. I got mine for about $20, and it does just fine for the limited number of times I actually use it. Just make sure you knife is shaaaaaaarp, because a dull one will tear the delicate fish to shreds.

Next, you'll need a pair of fish tweezers, which help pluck pin bones from the fillets later. The pair pictured here is a very standard type and works well.

Step 1: Remove Fins, Scales, and Guts

If you have a whole fish that hasn't been cleaned up at all, the first step is to snip off all the fins with kitchen shears, scale the fish, and then slice open the belly and pull out all the guts. Then grab the gills (they're easy to get once you've sliced open the belly from below) and rip them all out.

If you're able, though, I'd recommend having the fishmonger do this part for you, unless, of course, you've caught the fish yourself. Scaling a fish is incredibly messy business—the scales fly absolutely everywhere—so I'd try to avoid it if you can, or you'll be picking up errant scales for weeks after. The guts, meanwhile, are messy, and there's nothing to do with them but throw the away, so you might as well have the fishmonger do that for you. Snipping the fins makes scaling easier, so that might as well happen at the same time.

If you do want to scale the fish yourself, you can use the dull side of your knife, running it against the direction of the scales (tail to head), but it's even easier if you have a proper fish scaler, which makes a much better and faster job of it.

Step 2: Check for Scales

This may sound redundant, since the scales were just removed by you or the fishmonger in step one, but it's worth double checking—scales are literally armor, and even a few can make filleting much more difficult to do. I've yet to find a fishmonger that does a truly thorough job of getting all the scales off, and even when you've done it yourself, one or two often manage to slip by. There are a few spots where you're most likely to find stubborn scales: around the belly, the dorsal area, and near the head.

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You can use the dull side of your knife, scraping it from tail to head all over to feel for scales, or use your hands—either works. The knife may pry the scales off on its own, but often they're stubborn and you have to get in there with your fingers and pluck them off one by one.

Clean up as you go, making sure to wipe up any and all scales that litter the cutting board and fish. The cleaner you can keep your fish and your work area, the less you'll have to worry about scales sneaking into your food later.

Step 3: Slice Behind the Head

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Position the fish with its dorsal (back) side nearest you. Using your knife, slice down through the meaty section right behind where it meets the head. Make the cut angle in toward the head, since the meat extends under it a little and you don't want to lose any of it. If you cut too close to the head, the blade will run into bony obstructions; too far away, though, and you'll lose good meat.

Step 4: Remove First Fillet

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Now, with your knife, cut along the back (dorsal side) of the fish, right above where the bones are, moving from the head to the tail. Continue making nice, even cuts as you go deeper and deeper into the fish, separating the fillet from the bones below. Try to exert an even pressure on the blade so that it presses flat against the bones as you cut; this will help ensure that you get as much meat off as possible.

Be careful to keep your other hand away from the blade as you work: you'll have to move it around a bit, but placing it directly on top of the fish with your fingers flat is safest.

If you need to take a peek under as you go, you can gently lift the fillet; just be careful not to bend it back too much or you can tear the flesh.

Once you're halfway through, the knife will ride over the spine itself, and you'll sometimes hear and feel little clicks as it slips from vertebrate to vertebrate, cutting through pin bones that radiate off the spine.

Then keep on working towards the belly with those same long, even strokes of the blade, sliding it right on top of the bones that run around the belly portion. The fillet gets pretty thin here so it's easy to accidentally cut through. Just take your time, go easy, and keep that blade pressed against the bones as you go.

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Once you've gone all the way through, the fillet should come right off; if it's still attached somewhere, just use your knife to cut it free without damaging the meat.

Step 5: Flip Fish and Remove Second Fillet

Now it's time to turn the fish over and do the other side; once again, position it so that the back is nearest you.

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Make another cut behind the head, angling toward the head as you go deeper to avoid losing good meat.

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Working from about the midway point, slice along the back of the fish towards the head, once again right above the bones. Now turn your blade so that it's pointing towards the tail and slide it all the way through the fillet until it comes out the other side; make sure you press the knife against the bones as you do this. Riding right on top of the bones, slice towards the tail until the knife cuts the fillet free from the tail half.

Then turn the blade back toward the head and cut the fillet free, once again riding right on top of the bones with a gentle downward pressure, until you've gotten as far as the spine.

Once past the spine, take your time and search for a good angle to free the fillet from the belly bones. It can seem a little awkward at first but you'll get it.

When you're done, you should have two good fillets, plus a head and bone cage that have very little meat left on them. Save the head and bones for fish stock or soup.

Step 6: Trim the Fillets, and Remove Pin Bones

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The next step is to clean the fillets up and get them ready for cooking. I start by trimming the belly flaps off each one. The belly flaps aren't very tasty: they're thin, often have bones stuck to them, and sometimes a bitter flavor from the organs that they once contained. A nice, clean, even line is what you're looking for here.

I'll often also trim off the very bottom of the fillets at the tail end for a cleaner line there. And lastly, I'll slice off any bones that managed to come off with the fillets (usually hugging the surface on the head side).

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Then use your fingers to feel along the fillet where the spine was attached. You'll usually feel pin bones in the fillet, especially nearer the head end. Take your tweezers and very gently try to grab the top of each pin bone without digging into the flesh itself. Then pull each one free. It can help to use the fingers of your free hand to press down on the flesh around the bone as you lift it out, to prevent the flesh from tearing.

There's one little pin bone almost everyone misses, right near the skin on the head end. Get that one too, it's a pet peeve of mine when it's left behind.

Portion Fillets

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If your fish is big enough, you'll likely want to portion the fillets into individual serving sizes. There's no exact science to it, just cut at relatively even division points. Keep in mind that the fillet tapers towards the tail, so that tail piece may need to be a little bigger to ensure it has as much meat as the ones cut from the thickest part.

Now repeat this a few hundred more times, and you'll be able to do it with your eyes closed. Isn't that a cool party trick?