I'd like to add to that.
I agree that the most important thing is to control the fishery mortality rate, but how you fish and where you fish and when you fish is also of great importance. Technical regulation to ensure that your fishery pattern is good is very important so that you actually fish the right fish from the stock. As I mentioned, this is about mesh sizes and area closures and protection of juveniles, regulation on how much fish you are allowed to have under a minimum size. Those technical details regulating the fishery pattern are a little bit boring, but are very important in managing a stock.
The question of discards also comes into this. Discarding the small fish instead of avoiding fishing the small fish is not a positive way to do this.