“OMG! There are worms in my fish!”

SOSSEXI Blog: 9/1/12

I got a desperate string of emails this past week from a couple of my SOSSEXI friends and fellow shareholders asking if something had gone horribly wrong with the fish they received last Friday. You see, a couple of them had opened up their packages of flounder, ready to whip up a culinary masterpiece, and lo and behold, to their absolute disgust, they had found a small, blackish-grey worm or two on their fillets. Had this been my Mom, who is absolutely not a fisherman, she would have tossed the fish out immediately and said something like “that would gag a maggot!” as she speed-dialed the local pizzeria.

But hold on a minute. We’re in this CSF because we want fresh, local, sustainable fish. We’re like CSA shareholders who are one step away from being farmers, except we’re one step away from being fishermen. This is nature, people. This is not much different from the CSA shareholders getting their bag of veggies with some dirt still on them, maybe a cabbage worm still munching on one of the kale leaves, or a feather or dirt still encrusted on the egg shells in your egg carton.

As a life-long recreational fisherman, the “cod worm,” Phocanema decipiens, and the “herring worm,” Anisakis simplex, are something I am very familiar with. The intimate involvement of catching, cleaning and filleting your own fish takes away all the mystery, but I can sympathize with someone who simply loves fish, heads to a reputable fish market and comes home only to discover a worm on the fillets.To remove the mystery, let’s discuss these two “worms”, or nematodes, that are often present in fish such as cod, flounder, hake, pollock, and haddock, as well as whiting  and mackerel.

These nematodes’ life cycle begins in the stomach of marine mammals, most especially the grey seal found in the Northeast. Eggs pass from the seal to the ocean floor where they are consumed by crustaceans, most often shrimp. The shrimp is a major food source to the cod and flounder we love to eat, and as they consume the shrimp, they consume the nematodes. The cod and herring worms can burrow from the stomach of the fish into their fillets. The life cycle of the nematodes is closed when a seal then eats the infected cod or flounder. Too much detail? I know, it’s a little gross, but let me tell you, this life cycle has been going on as long as there have been seals, shrimp, and fish. You just didn’t know about it. So now let me tell you how the fish processor and fish market shield you from this less-than-savory side of eating fish.

When the fishermen bring their cod, haddock, flounder, etc to the processor, the fish fillets go through a process called “candling.” The translucent fillets are placed over a candling table, which is a glass surface illuminated from below with white, fluorescent lights. Worms show up as dark shadows and are quickly disposed of with tweezers or the tip of a knife.

As with any quality control process, some worms are going to slip by the processor. My husband worked all through high school at a highly respected fish market called “Hills Seafood” on the Main Line outside Philadelphia, and he distinctly remembers holding fillets from the processor up to the light to detect any stray cod worms. He would dispatch of them with a sharp knife tip, then place the fillets in the case for sale to the public. The fish monger is probably the last line of defense to protect and shield the public, although even then, some worms may get by. They are unsightly, and consumers naturally object to their presence.

The good news is that the worms are relatively harmless if consumed unknowingly by the public. Cooking a fillet for only 1 minute at 140 degrees will dispatch any worms, and if you freeze your fish for 60 hours, all worms will be killed. A brief note, though, is that consuming raw fish of these species may open your stomach up to a variety of nauseous and vile ailments if these worms are present. I’d probably stick to the tuna sushi and forgo the cod, but that’s just me.

When I talked to one of our own SOSSEXI fishermen, Frank Mirarchi, he said the fish processors have seen an increase in the number of worms in fish recently, and that it has resulted in an expenditure of “an enormous amount of labor removing these parasites from fish.” The thought is that the booming increase in the seal population has naturally lead to an increase in the cod and herring worms. If you walked down the beaches of Monomoy as I have, ten years ago you would have seen a handful of seals and probably said, “Wow. That’s neat.” If you walk those same beaches today, there are thousands of seals lolling around, and it’s not so fascinating. Food for thought next time you hear the cry to save the seal, but that’s another discussion.

As shareholders, we need to be prepared for the possibility we may find a worm or two in our fillets. Their presence is a natural occurrence and by no means indicates we are getting a spoiled, unsanitary or un-fresh product. As a shareholder, you are now a part of the process. Don’t be afraid. As I cleaned and de-veined a couple of pounds of shrimp for shrimp cocktail last week, as I am sure many of you have done before, I realized this was a good example of how we as eaters participate in preparing our food and removing something unsightly and unsavory. If you can do that, you can make quick work out of a cod worm or two!

Submitted by Kathleen Wright






About eSS&SC

The South Shore and South Coast has been home to hunting, gathering, fishing, farming––and great eating––for over 10,000 years. We are committed to identifying, devouring, and sharing all that Southeastern Massachusetts has to offer today and preserving local options for future generations.
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7 Responses to “OMG! There are worms in my fish!”

  1. DanD says:

    Well put. Too many people on the internet share their disgust at having found a worm in their fish. This is a sensible article that puts it in perspective and helps explain that it’s not a big deal and can be dealt with easy enough. And you’re right, if folks were more involved in where their food really came from they wouldn’t have have such a problem. After filleting a bunch of cod, the sight and removal of the worms becomes no big deal.

  2. Jane says:

    I mean these parallel, dark lines at some sea or river firshes – such as these on your 3rd photo.

    I apologize for such a question, but there is now many problems with nematodes.


  3. Jane says:

    Dear Sir,
    I see that you have a big knowledge about fish and worms they may have. That is why, if possible, I would like to ask you one question.

    Nematodes are worms that are usually white or brown and they are often rectangularly coiled. But more and more often when I cook or bake a whole fish without opening it before, I see something such as is visible on your 3rd photo (that one, where you are just opening your fish): very thin lines of brown colour, plenty of them, going through white muscles from up to down the fish. On your raw fish it has yet grey colour.

    At first I thought that these are vessels. But after I noticed it is not in the Pacific Ocean fish such as e.g. icefish or you not see them in salmon. I know that species may vary, but I become afraid of, whether these are not nematodes? Especially that now many fish has it.

    Thank you in advance.

    Very good and interesting article, thank you!

  4. Theo mclelland says:

    Many times I’ve stayed over Craig’s before he got hitched and he would make scrod the next day my job was to check for worms they are no big deal at all

  5. gadusgirl says:

    I’m a PhD student working on predator prey relationships between grey seals and groundfish along eastern Canada and weaving the biology with the socioeconomic variables related to small fishing communities. Right now, I am focusing on collecting some data from food processors regarding infection rates. The situation sounds quite dire, especially in terms of labor costs compounded by sharp drops in production. There are reports of nematodes showing up in fish species that never presented these parasites 25 years ago. I would be very interested to know how the situation along New England pans out with the New England grey seal breeding colony (you can thank Canada for that as I believe the genetics work has resolved that those seals originally came from Sable Island).

    • @gadusgirl- Your work sounds really interesting, and I would love to chat with you. I have some information and contacts for you. Send me a message on Facebook to Kathleen Fitzpatrick Wright and we can exchange information. Thanks for the comment.

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