Sadly farm fishing as it stands now relies on the bulk catch of wild fishing. Farm fishing is a machine to turn unsalable tralled fish into commercially desirable delicious fish. Fish farming cannot yet exist without wild trawling.
It is something which is worked on, on several fronts. Replacing fish meal and oil with insects, mussels, vegetable based products, etc. There is less fish meal and oil than a few years ago in fish feed. Here is one example of the work. My company also just got a government grant to work on this.
Well, let's stop consuming fish, because maritime ecosystems, stop meat because animal cruelty and global warming, stop soy because rainforests and genetic manipulation, stop rice because methane emissions, stop potatoes because neophytes in most of the world and stop lettuce because low-calorie waste of precious land.
I guess that leaves us with wheat and soylent green...
Answers like yours are just cherry-picking some approaches to support your favourite solution, veganism. There are many more of those kinds of problems, stemming from a common one, overpopulation. Any linear approach reducing consumption of something glosses over the fact that world population is still in exponential growth, and factors influencing that are barely understood and at best handwaving arguments about expected slowdowns are provided. Veganism is throwing a hotdog at a herd of hungry lions here...
the world is not in exponential population growth - the rate of growth has been shrinking for two generations. global population decline will happen in my lifetime. the demographic transition happened centuries ago in some countries. fertility rates are falling faster than any of the overpopulation monster-in-the-closet analyses assume, why are you afraid of overpopulation?
Wild populations should be left alone entirely.