I noticed that when fishing for 6 inch pollock by jigging sabikis up and down a pier in galway on holidays last year that when
the clouds bloched out the sun all the fish were hooked in the mouth but when the sun came out all the pollock were foul hooked
So I think that pollock wise up to a lure very quickly and once they wise up to the lure or can see the lure very clearly the only way to catch them is by foulhooking them, hope this helps,
Goldfish