Here's an exerpt from the above link to the article I referenced.
Are round worms dangerous?
There have been cases of human illness caused by the ingestion of live Phocanema or Anisakis larvae in countries where raw or lightly cured fish is commonly eaten. By 1980, there had been only one reported case of illness in the United Kingdom caused by larval round worms from fish; this is because in the UK fish products are normally cooked before consumption. Phocanema and Anisakis larvae are killed in 1 minute at a temperature of 60?C or over. In practice this means that cooking a fillet 3 cm thick for 10 minutes at 60?C will kill any worms present. The temperature of a cold smoking process, for example kippering, is not high enough to kill parasites, but in a commercial hot smoking process a high enough temperature is usually maintained for long enough to kill them. Freezing of fish at - 20?C for 60 hours kills all worms.
Anisakis larvae are resistant to salting; immersion in 80? brine, 21 per cent salt, for 10 days will kill all larvae, but in brine of lower strength they can survive for much longer. Anisakis is also resistant to marinating. When there is any doubt about whether Anisakis will survive a process it is safest to use frozen fish. The ability of Phocanema to withstand salting or marinating is not known, but it is probably similar to that of Anisakis.
Anybody want to do sushi for lunch?
By the way, most home freezers reach -16 to -22?C. In my lab we have freezers that are held at -40 and -70?C. We also have what's called "quick freezers". These are chambers which have tanks of liquid nitrogen attached. Nitrogen gas becomes liquid at tempertures between 65 and 77? kelvin....burrrrrrr....... I'm sure you've all seen the demonstration where the science nerd (lab boy) dips a flower into liquid nitrogen and then bangs it against the counter and it shatters. I dip my technicians hands in it. :)
Bait, one other thing I forgot to mention in my previous post was that the number of parasites are also tied to both size and age of the fish. The larger and older cod have more worms. Kind of intuitive if you know that the laval cyst, stage of life while in cod, is dormant and remains in the cod's tissue until the cod itself dies.