The answer has 2 components

1) the level of acceptable exploitation on non-target species. A cap must be set on by-catch whether incidental outright mortality or release mortality or both. Fishing stops when the cap is projected to be met. I believe this is the "standard" you are looking for. It also happens to be a highly variable number depending on the stock in question.

2) an accounting of the kill rate of every gear type deployed in the fishery. Less fish fish-friendly gear types will obviously burn thru the exploitation cap faster… they should have limited if any time on the water