The best thing for the fish is clearly to leave them alone. Anything other than than is a compromise that harms them for our benefit. If the question is, as it should be, can the run sustain whatever final form this harm takes and continue to "succeed" I think the answer in this case should be no. Fishing over an imperiled run with a theoretical 500 fish buffer between success and failure is too small a margin. Give the fish the benefit of the doubt and make a conservative decision.

I for one would happier knowing that they are there than I would be fishing for the last one.