Tackle and Tactics
It is a few years since I gleaned this information and it seems likely that, nowadays, things are much improved. However, the dangers of eating fresh, uncooked fish are still very real. So, if you enjoyed the film "Alien" read on.
I’m a city lad, originating from the back streets of Leeds, so it was, I suppose, inevitable that fish and chips made up a fair chunk of my youthful diet. In fact, the intense competition between the many chippies raised the frying of cod in batter almost to an art form.
Now, as far as I’m aware no one in England ever suffered any ill effects as a result of eating a crisply cooked fillet. But had I come from the Japanese city of Tokyo, instead of Leeds, it might of been a totally different story so far as my own digestive tract was concerned. At the time this was written (the 1980's) every year around one thousand Japanese people woke up in the early hours of the morning suffering intense stomach pains.
Rushed to hospital, vomiting and bleeding, an internal examination reveals that the stomach wall of a victim is a mass of ulcers, with each ulcer the focus for a bundle of little wriggling worms. Almost invariably the surgeon’s questioning shows that the victim’s last meal consisted largely of sea fish from the local Sushi bar.
The Japanese prefer their fish uncooked, and most of the cod, tunny, mackerel and herring which form a large part of this raw fish diet are fresh from the sea and have never even seen the inside of a frying pan or a steamer let alone a deep fat fryer. The fish probably will have undergone a minimum of chilling, freezing or preservation.
This passion for “wholesome food” would be all very well if it were not for Anisakis and its relatives. These creatures are parasites found in dolphins, porpoises and seals throughout the world. They are worms, the adults of which infest the guts of these marine animals, where they often accumulate like ropes of knotted spaghetti.
The main purpose in the life of the worm is to lay as many eggs as possible. These eggs pass out with the droppings off its host and sink to the bed of the sea. Every egg represents a future parasite, but before it can mature it must survive a whole series of exciting adventures.
First the larvae, which hatches from the eggs, is swallowed by a crustacean. Shrimps, crabs, krill and copepods are all potential hosts. Once swallowed, the worm forms a cyst and settles down in wait.
The infected shrimp, unaware of its uninvited lodger, carries on its business as usual until, in an attentive moment, it falls prey to a pouting which comes across its luckless quarry foraging over the sand in the dead of night. One quick swallow and the shrimp is devoured together with the worm.
Given a new, larger home, the worm is now anxious to inspect its sparkling new surroundings, and it burrows through the wall of the gut and takes up residence in the body cavity.
The poor old pout, also blissfully unaware of its guest or, more likely, its guests, remains with its shoal-mates, feeding at night and resting during the day. However, it soon begins to feel a little off colour, with perhaps a belly ache or headache, and when the group comes under attack from a shoal of marauding cod it is not quite as quick as its mates, and finds itself the victim of a cod. One could say it feels “down in the mouth”, literally!
Once again its “all change” for the parasite worms again get restless and bore out of the cod’s stomach and in to its muscles.
Now the family of worms prepare for their last move. They wait, patiently, until the cod is eaten by a seal, porpoise or dolphin. When that happens Bingo! They hit the jackpot, and they feed, grow, mate and lay more eggs which are passed out through the carriers droppings and the whole process begins again. Its a non stop merry go round for Anisakis.
Once in the cod, Anisakis finds some portions of the fish more attractive than others. The muscles above the backbone rarely contain any worms, where as the flanks may have quite a few, and the thin layer of flesh which surrounds the guts will often accumulate a heavy load.
Back to the problems of those Japanese with stomach ulcers, and the obvious question is; why should a parasite which normally lives in seals and dolphins have such an horrendous effect on humans?
In fact, when the worm larvae finds itself in a human stomach, where conditions are not quite up to scratch, it is able to make the best of a bad job with the resultant painful and unpleasant consequences. But although most parasites are beautifully adapted to life with in their host it is not in their best interest to kill or injure the creature upon which they depend for their existence that is not their intention. It just happens that the side effects are particularly unpleasant when the victim is a human.
In the 1960’s there was a bad outbreak of Anisakis in Holland. The Dutch have always enjoyed eating raw fish, particularly herring. And in the early 60’s fishermen began landing ungutted fish instead of cleaning them at sea.
This gave the larvae time to crawl from the gut cavity, where the bulk would normally be found, into the muscles of the fish, which were in turn being eaten by the population, together with the worms. The problem was eliminated by ensuring the fish were frozen soon after being netted, and kept frozen long enough to kill the baby worms.
What is particularly interesting about this rather complicated story of Anisakis is the unique set of conditions necessary to ensure its survival. Yet it still manages to flourish.
Until the day comes when we all prefer raw fish flesh to a nice fillet of fried cod we should be more or less immune from the gut gripping effects of Anisakis. However, any gourmet who is tempted to try and prepare themselves a traditional meal of sushi or (strictly speaking) sashimi, using their latest catch of cod as the basis, should be aware of the possible consequences!
If you have any comments or questions about fish, methods, tactics or 'what have you.'get in touch with me by sending an E-MAIL to - firstname.lastname@example.org
Tilapia and chips!