Keem Bay, Achill 10.9.2016

The spearfishers don't wipe out fish stocks per say.
It's a strong possibility the fish see them as a new predator in the water and simply clear the fek off out of it.

I've watched a good few spear fishing vids on yootoob, the fish couldn't care less about the spear fisher most of the time. The majority of fish just carry on about their business, the rest seem to come over to the spear fisher for a look.
So no, I don't think your theory holds water either to be honest.
I'm sure we're all of the opinion that a seal in the vicinity of where we're fish can have a detrimental effect on the fishing (not always though), well a seal is a lot more effective as a predator than a spear fisher, however, it doesn't mean that a mark is spoiled long term just because a seal made a visit.
A resident seal could make a difference I would have thought though and any time I've visited Keem there's been at least one seal about.

We're all entitled to our opinion and since you've watched loads of videos on youtube i bow to your superior wisdom.

Backed up by a lifetime of fishing and diving, a degree in fish biology and fisheries management, years working in public aquariums for starters.

What's your opinion based on?

My opinion is as valid as yours or anybody else unless you can prove otherwise.

But you have already agreed that mine is correct.