Eat less of it and buy the expensive stuff. Expensive = better margin = less fish needed to pay the wages, and 99% of the time expensive = high end sustainable

It's not bulletproof but it's a good rule of thumb, I eat fish once in a blue moon, last time it was a can of "traditionally hand fished" tuna, 40 euros a kilo

If it's cheap as fuck there is no way it's sustainable, you're either abusing nature or fellow humans, or both