I'm gonna go with overfishing. Anyone who has been shopping since the 1990's has seen fish diversity decline and prices skyrocket beyond inflation (not to mention a sharp increase in farmed and faux-colored fish like salmon). Illegal fishing is impossible to combat.
See China's illegal fleets:
[1] https://news.ycombinator.com/item?id=27412691 [2] https://twitter.com/epineyro_ok/status/1378112721628114947
Commercial fishing also had no hard limits back then, and so we eradicated the redfish population and most of the specks. We now have pretty substantial limits on how many of each we can keep when we go fishing, to the point where you're doing it just for the experience because you won't catch enough to recoup the gas money.
This is because the water became so polluted that families no longer thought that it was safe to be in. It's been decades now and the water quality is just starting to be clean enough to swim in again.
I don't think a few years would cut it, the Grand Banks are juuuust starting to come back after almost 30 years of nearly no fishing.