There is probably no food more associated with (Ashkenazi) Judaism than lox. The very word lox came into American English from לאקס
in Yiddish, the word for salmon, which our ancestors have eaten since living in Eastern Europe.
Now Rabbi Moshe Karp (yeah, you'd think it's a joke, but this guy exists), the Rabbi of the ultra-Orthodox West Bank settlement Modi'in Illit, has ruled that halibut, salmon, flounder and various other fish can no longer be considered kosher, because the roundworm anisakis parasite lives in these fish.
The thing is, the Gemara mentions this (Chullin 67b),
תולעים דרני דבשרא אסירי דכוורי שריין
which means (after looking up all but the third and fourth words in Rav Marcus Jastrow's Talmudic dictionary) Parasitic worms are prohibited in meat (i.e. mammal meat and perhaps poultry) but permitted in fish. According to Dovid Bistricer of the Orthodox Union, the Shulchan Aruch and rishonim say the following:
Mature insects swallowed by fish are considered sheratzei hayam and are prohibited, while insects grown inside the flesh are not considered sheratzei hayam and are permitted until they exit the fish into the ocean. Although the Rambam (Hilchos Ma’achalos Assuros 2:17) makes a distinction between insects grown inside flesh while the fish is alive and while it is not, the position of all other rishonim is that insects grown inside the flesh of fish are permitted even when the fish is alive. The Shulchan Aruch Yoreh Deah (84:16) rules clearly that all insects found in the bellies of fish are prohibited, while those found in the flesh are permitted.
According to the Center for Disease Control, the anisakis does not reach mature form until after its fish host is eaten by a marine mammal (or a human if improperly cooked)
Yet Karp makes the outlandish claim that new scientific evidence says otherwise:
According to the OU’s Rabbi Goldberg, at the end of the meeting in Brooklyn, a chassidishe rebbe in attendance asked Karp if he was implying that gedolim of yore ate treif. Rabbi Goldberg said that Karp explained, “they did not know what we know and that the fish is assur (forbidden) because we know how the bug works.”
“I asked him to please tell me the name of the Jew or gentile that clarified it for us and where is this research, and when was it put out,” recalled Rabbi Goldberg. He believes the idea of a ban will soon be sleeping with the fishes. “If you say something is based on science then you have to provide the science.
Now, never mind that Rabbi Moshe Feinstein wouldn't even write a teshuva on this because he felt the Shulchan Aruch had already fully answered it. Never mind that whenever science says something about the age of the Earth, causes of earthquakes, etc., Haredim always condemn the science in favor of what Chazal (the sages who wrote the Mishna and Gemara) said. Looks like the Haredim in Israel are going for it , and the ones in Monsey and Lakewood will follow. One hopes the Orthodox Union at least continues to have more sense than this.