I was all set. The miso glaze had been prepared by my wife the night before and I had just unpacked the boxes from our go-to food delivery source, FreshDirect. An impeccably clean package of two pounds of fresh cod, without a hint of odor, rested in front of me on our Caesarstone counter.

I unwrapped the fish, preparing to marinate it for an hour. As I admired the glistening flesh, I noticed something that looked like a worm. I took a knife and separated the flaccid half-inch strand from the fish and placed it on the orange cutting board. It looked a little like what the intestines of a Barbie doll might look like.

I examined it more closely. I wasn’t sure. And then it moved. But it didn’t just move. It waved its head, or its butt—it could have been either—in a tsk-tsk fashion, or as if it was slowly waving a flashlight. I cringed.

Now, believe me, I’m not the squeamish sort. Little critters don’t usually get to me. And yet, I didn’t know if this fish was contaminated, so I threw it in the fridge for later review. Maybe it wasn’t as glamorous, but that night’s dinner—miso glazed tofu with broiled asparagus and rice—seemed like an adequate substitute.

After the dishes were done, I looked up “cod” and “worm” on the Internet, and saw that I was not alone. There were a variety of threads and images on flickr, Chowhound, YouTube, and elsewhere, all confirming that this kind of worm is prevalent. So much so, in fact, that they’ve got a name for it: cod worm. Apparently, it’s not a danger to humans because when we cook the fish, the parasite dies. I guess this explains why I’ve never seen cod sushi.

We complained to FreshDirect, which was quick to respond. A member of the customer service team gave us a refund, and noted in an email:

I'd like to take this opportunity to advise you that worms found in cod and monkfish are not uncommon. In fact, this has affected the industry for decades. No matter how much the product is cleaned or "candled," as the industry calls it, there may still be traces of worms found in such products. Once cooked, these worms pose no harm to a human when consumed.

 I was curious if this was the industry party line, so I called several restaurants and well-known purveyors of seafood, and, not surprisingly, didn’t get many people to talk with me on the record.

Whole Foods, however, gave me this statement:

Nematodes are naturally occurring parasitic roundworms common in coldwater, oily fish such as cod. Nematodes are not harmful when fish is cooked properly to an internal temperature of 140°F, which normal cooking techniques generally exceed, or frozen if intended for raw consumption. 

Our seafood suppliers use the best control measures to guard against nematodes reaching our stores, but sometimes this does occur. If shoppers are unsatisfied with any product, it can be returned for a full refund. We work hard to ensure that our products are of the highest quality and we want to ensure that our shoppers have the best shopping experience possible. 

The people with whom I spoke had a “What, me worry?” response. Fiona Robinson, the editor of the trade publication SeaFood Business was kind enough to take me seriously and not call me a wimp, but she likened the worm-in-fish issue to dirt on lettuce.

“I guess that depends what’s in the dirt,” joked Graham Sherwood, who, as a research scientist for the Gulf of Maine Research Institute, studies cod in Maine. But he didn’t disagree with Robinson’s sentiment: he said that the parasites are “not a major concern.”

Maybe not to you guys, but it creeps me out. Dead or alive, I'm not into the idea that a worm means more protein or two meals in one.

It really comes down to numbers: just how "not uncommon" the worm is in the fish we eat. Sherwood directed me to a paper put out by the Food and Agricultural Organization of the United Nations about the cod worm (it’s actually officially a seal worm, but it’s more often called a cod worm), which indicated that there is an international standard allowing no more than five worms in about two pounds of fish—when the worms are at least a centimeter in length. (So, if they’re shorter, no one cares?)

That seems like a pretty low standard. I doubt most patrons at restaurants realize the odds they’re playing, but that's partly because the actual percentages are indeed unclear as far as I could tell. And yet, the fishing industry is clearly working to control the problem. Sherwood told me that fishermen try to avoid places where the “wormy” fish are (farther out to sea tends to be better), but they can’t avoid them entirely. And the candling process is the industry standard, according to Robinson, who described the procedure: After the fish are filleted, they are placed on giant light boards and examined. The worms are picked up in the bright backlight, and, when found, are excised. Of course, human error accounts for some worms getting through, like the little guy I met.

With food, as with many things, we dance on the spectrum between ignorance is bliss and knowledge is power. Where do you stand? I don’t want to spoil my beloved fish & chips for everyone out there (sorry, in a cruel twist, haddock also gets the cod worm), but, then again, we all know that the oceans are being overfished, so the cod might just benefit from a good backlash.

Alas, if you, at this very moment, happen to have a cod sitting in your refrigerator (or frying pan), I’d suggest you not put it to waste. Just don't look too closely at it.

As for me and my family, we won’t be ordering cod any time soon. But that's because of what happened the night after our miso-glazed tofu. I took out that same cod with a determination to give it the beer-battered frying of its life so that I’d know for sure that nothing would be wiggling on our plates.

With a steely gaze, I took the fish out of the fridge and placed it on the counter near prepared plates of panko and egg batter. But my curiosity got the best of me.

I poked a little here, and parted the flesh there. And there was one. And another. And another. Soon, I had five new friends waving indignantly at me.

We ordered pizza.