Daas Yochid: It is a pleasure to carry on a polite and intelligent discussion of the issue.
“we have to deal with the issue of why they don’t obtain the status of the krill (as part of its flesh) and should be assur.”
An interesting idea. Why would we look at the worm as the same as the fish? The heter say with a worm in n apple is a gezeiras hakasuv of shoretz al ha’aretz, and not that the worm gets the din of an apple. If one needed to eat an apple worm for sakana reasons would he say borei pri ha’etz on the worm? Would someone eating this worm that was poresh from an apple receive malkos for tevel and orlah in addition to the multiple malkos for sheratzim?
“It is also unclear why, if we find them in the large fish (i.e salmon) at a visible size, we don’t assume that they were swallowed directly as a free swimming creature.”
The scientists who research parasitology claim that the life cycle of the anisakis composes of 3 larval stages in at least three different species of fish, Since it doesn’t contradict Chazal, I see no reason to disbelieve it. Presumably a fish the size of a salmon would not bother eating tiny krill.