Although many may think aquaculture may take away commercial pressure on the wild fish stock to achieve sustainability, that is not necessary the case. Think of this scenario.
Unlike the Asianic world, most of the western farmed fish are carnivorous species like salmon and steelhead. Carnivorous species has a higher trophic value (top of the food chain). To ensure the operation is profitable, you decrease the growth time to reach the optimal harvest size. This means, lots and lots of food. Where does this food come from? From the wild of course. The demand of food eventually drains out the wild stock's prey population. This can possibly pose as a bigger negative impact than a properly managed commercial harvest. On top of that, biological pollution poses a threat to the wild.
Hard to sum up such a big topic in a small paragraph. If anyone wants to find out more, I can send you the references.