Since this is a theoretical question, I have a theoretical answer.
The conundrum is the low test of traditional monofilaments. That is where the ethical question comes in. However, there is a way around that. If a stronger material could be found, it would no longer be a question of ethics.
I guess I would try for them with a super line like Fireline Fused Crystal micro ice in 3 lb test. It is 7X diameter.
Fused polyethlene was sold by Orvis as tippet material in the 1990's but it never caught on. It is so limp it is difficult if not impossible to lay out the tippet on a cast. But in case like you describe, I think I can make it work with a downstream parachute cast to line up with the narrow feeding lanes that big fish occupy when feeding on midges.
3 lb test is about what Cortland 5X Nylorfi tippet material was in the 1980s and it could land 20 inch fish without over stressing them. 3 lb test is not a problem because the tiny hooks that only a 7x tippet can thread may not even take a 3 lb pull without breaking or opening up.
---------- Post added at 10:26 PM ---------- Previous post was at 09:59 PM ----------
Originally Posted by wtl
I think unethical is too strong of a word here. It is certainly not optimal from a catch and release perspective. But look at it this way, what if you are blind casting with 7x, and hook a 20 inch fish? Is that suddenly unethical? Should you just cut the line? Probably not.
Lets give this a bit more thought.
I agree it is not unethical if you unintentionally caught the fish. However, in my view, this is not ethically the same as intentionally
fishing for that fish.
I think in this case, intent precedes action in determining the ethical nature of the action.
If they were ethically the same, then accidentally snagging a fish would be the same as intentionally trying to snagging a fish.
I would go one step further. Intent precedes content and action. One does not have to even have to snag a fish. The act of trying to snag is by itself unethical behavior. If that is so and if catching a large fish on too light a tackle is unethical; then it follows that the act of fishing for large fish with too light a tackle is unethical.