Sushi, Ceviche, & Parasitesby: George Van Zant
I almost threw up the first time I saw a worm back out of fish carcass. At the age of 13, on Belmont Pier I had just filleted a 15 inch halibut and while the skeleton carcass reclined on the fish cleaning board a worm crawled out from between the rib bones. Upon close perusal I discovered many more of these worms neatly imbedded in the left over flesh between the bones. Ugh! Quickly grabbing the carcass by the tail I sent it back to the waters below. I held the cleaned filets to the light and discovered about 3 more inside the four filets. They were also sent back from whence they came.
An old timer regular to the pier witnessed the whole thing and immediately chastised me. "Those worms wont hurt you boy, they add taste to the meat!" I was to hear that remark many, many times in the future "Besides, normal cooking of the meat destroys all parasites, worms or otherwise." Yes he was and is correct. Even though for me it is still difficult to keep a fish with critters crawling all over his body.
After this incident no fish escaped my worm search. I have found parasites in every single Pacific Ocean fish I have caught over the years. The worst infestation I have seen was the Isopod parasites that infested the newly planted striped bass that were planted in Alamitos Bay a few years back. They chewed on the fins and the tail unmercifully. I caught lots of the planted stripers and every single fish had only a nub for a tail left. These parasites also loved to exist, stuck to inside the gill covers, eating away at something not really obvious to the eye. I released every fish I caught after pulling off the inch long suckers. Sometimes I found as many as 10 leeches on a 12 inch fish. They were ugly, looking like a giant sow bugs with hooks on the ends of each segment of their body.
Usually parasites donıt bother the host. They feed upon them in such small amounts the host fish really arenıt bothered by them. As far as we are concerned, all parasites are destroyed with normal cooking procedures and most people cook all their food without any intention of eating raw meat unless itıs very rare cooked steak. The only people that I know of that ingested raw meat was the Indians and early Mountain Men. They ate the warm liver out of a freshly slayed Buffalo. Maybe thatıs why their life expectancy was about 40 years.
There are six different varieties of parasites that infect our Pacific fish.
1. Protozoa: These are microscopic organisms found in most Pacific Coast fishes. They can be seen when they form cysts about the size of rice grains. They are found abundantly in boccaccio. (salmon grouper, slimeys). This parasite is harmless to humans.
2. Leeches: They look like worms with a head on each end. They slit the skin of the host and ingest their blood.
3. Tapeworms: Adult tapeworms are found in the intestines of many marine animals. They range in size from an inch to more than a foot in length. They are most often seen crawling from a fishıs anus when the gut is accidentally cut while the fish is being cleaned.
4. Copepods: "Fish Lice" can be seen scuttling across a fresh caught fishes exterior. Some varieties permanently bury their heads in the host, when the skin heals over they are permanently attached to the host.
5. Isopods: These are the critters that infested the striped bass that we caught,
6. Roundworms and Flukes: These are the ones that get to humans. The disease is called "anisakiasis" or "codworm" or "herring-worm" disease. If you eat active larval stages of this particular roundworm the larva, finding itself in a non marine environment starts burrowing into your stomach or intestinal wall. This creates lesions on the stomach wall and somebody has to go inside and pull the little critters out. This used to done with major surgery but can now be done with fiber optics. Oh goody!
Most countries that do commercial fishing are required to freeze fish at 4 degrees for 24-60 hours if they are to be consumed in a raw state. This kills the larva and lets those that want, eat their raw fish.
Contrary to popular belief, acidic or brine based marinades are not strong enough to kill the roundworm larva, so ceviche dishes can also cause problems. Basically, if you plan to eat raw fish, it comes down to this: 1) examine and remove all the larva from the flesh or freeze it for 24-60 hours at 40 degrees. 2) cook or smoke the fish thoroughly. 3) donıt depend on pickling, curing or home refrigeration to kill the larvae.
P.S Donıt hold a filet up to the light searching for larvae in a Sushi Bar while the cook has one of those large knives in his hands!
Added: Fri Sep 05 2008