I would argue that not eating fish is not the solution. We can eat fish that are farmed or fished sustainably with minimal and sustainable environmental impact. A World exists where that is all fish. However without regulation, fish will be farmed using polluting methods, and fished in unsustainable and polluting ways, because it's cheaper and there's more profit to be made.

Voting with my wallet for sustainably farmed fish doesn't really affect anything either - this will always be a niche, high-end market that's unaffordable for most unless the fundamentals at the bottom end of the market change.

Fish is not the issue, fishing is, and only global regulation of the fishing industry can resolve the issue of (that industry's contribution to) ocean plastic pollution.