I suppose the good news is that jellyfish that will step in to fill the niche don't care about sound.
Maybe state funding for privateering navies given license to sink illegal fishing boats would be a good start. Trawling and other wildly destructive practices funded by various south asian countries are doing incalculable harm all over the world. Sink on sight is an appropriate policy.
Humanity has to get their shit together, or jellyfish will be all that's left.
Imagine someone set up a radio or a noisy machine somewhere in your own vicinity and you had no choice but to listen to it (even at a low volume) all day and night, perhaps for the rest of your life. Tests might or might not show that you were stressed, but you most certainly would be.
Perhaps I am biased from regular snorkelling and enjoying being immersed n a different natural world, and for sure I do have tree-hugger tendencies. But I find it extremely arrogant that our species thinks it's acceptable to inject noise pollution into an environment inhabitated by thousands of other species.
All that to say, I certainly understand the concern. But I would personally have to see evidence of harm
Otoh, some people purposefully setup noise machines to improve sleep and reduce stress. Sometimes a small amount of noise is a good thing.
Uhh... I don't consider myself an eco-hippie, but that "mitigation" sounds like a euphemism or sinister "mitigation of negative PR", rather than actually literally doing less damage.
Like: "Gradually make things worse so that animals flee on their own, and if they die of starvation at least it's somewhere else so it won't make the local news with kids finding corpses on the beach."
But their modem[1] uses NATO's JANUS standard[2], which communicates at 11.5 kHz, which is just audible to humans, but well within range of marine mammals[3].
1: https://www.subseapulse.com/products/ 2: https://spectrum.ieee.org/nato-develops-first-standardized-a... 3: https://en.wikipedia.org/wiki/Hearing_range#/media/File:Anim...