I understand the reluctance to stop practicing minhagim even when the original reason is no longer applicable. This attitude is generally a nice way to practice.
Nevertheless, if someone eats meat and gefilte fish from the same plate or with the same fork, I see nothing wrong with this practice. It is not a sakanah, and no research needs to be done. Certainly no more than research must be done to determne whether raisins in corn flakes is a sakanah, or bananas in jello. Let’s give credit to modern medicine, we all abide by its instructives.
The practice of removing all fish related items from the table before bringing meat is an unnecessary exagerration of this no-longer applicable minhag. If it is because “minhag yisrael kadosh”, then by all means do that. But those who do not practice this way are totally in the clear.