The world reached peak fish catch in the mid-90s. [1] And we now eat more grown fish than caught fish. The problem is that with increased acidity in the oceans, as part of the ocean absorbing mor CO2, we get less algae and eventually less fish. [2] But, yeah, let’s keep fishing until the stocks collapse. [3] They take a very very long time to recover.

[1] https://ourworldindata.org/grapher/capture-fisheries-vs-aqua...

[2] https://www.ioc.unesco.org/en/articles/ocean-acidification-t...

[3] https://en.wikipedia.org/wiki/Collapse_of_the_Atlantic_north...

What makes it even more ridiculous is that one could think grown fish are a fine solution over-fishing.

But it turns out, many fish farms use caught fish for (part of) the fishmeal and fish oil used to feed the fish they grow. Because many fish we eat turn out to be pescetarian.

Ocean acidification is much more complex than "less algae and less fish." In fact some algae and bacteria will have giant blooms partly as a result of that, warming, and Nitrogenous runoff. Giant blooms consume oxygen in the primary marine trophic levels, causing die-offs that liberate more nutrients, leading to hypoxic and even large anoxic zones. You also have the concern that acifification can lead to (at first) worse outcomes for organisms depending on carbonates, and eventually (potentially) their extinction.

All of this assumes that we have a pretty solid understanding of what this system looks like as we wrench it from one feedback loop into another, but it's the best we've got.