Current fish wet biomass is about 2 billion tons, so removing them won’t make a dent either. (Marine fish biomass dropped by 80% over the last century, which—taking into consideration the growth rate of the world’s shipping fleet—leads to an odd conclusion: Sometime in the last few years, we reached a point where there are, by weight, more ships in the ocean than fish.)
In regulator-speak, this portion of the fish trade is dubbed IUU: Illegal, Unreported, Unregulated. IUU fish can include everything from a striped bass that local fishermen offload to friends after they catch more fish than quotas allow to a live lobster that comes in at less than one-eighth of an inch below regulation. But by far the biggest IUU problem is the many tons of international fish that pass through multiple foreign ports and are intentionally mislabeled to fetch a higher sales price or avoid detection as an overfished commodity. The former is an issue that exists at the species level: It’s likely that haddock filet you bought for dinner isn’t haddock at all.
https://medium.com/food-crimes/piracy-and-politics-at-the-ports–20f55a681ce5