They do, but they continue increased restocking efforts to maintain the fishery. I have seen actually a new releasing method other than farming of cod fingerlings. They actually release fertilized eggs directly to the kelp forests near the shore. In order to obtain a permit and fish the spawning season (otherwise closed for fishing), the commercial fishers are required to bring a fraction of live and healthy females and males from their catch to the county office, equipped with live tanks and located in the same port. Then, the county officers would fertilize the eggs by mixing eggs from females and males in a set ratio and release as explained.
Most nearshore commercial fishing for cod in Korea is done through the pound-trap nets. Bottom dredging and trawling inshore is prohibited and discouraged even in offshore by restrictions and economic profitability - operational cost is too high. And it has been a trend in the Korean commercial fishing in general as I explained in the example of bounced back Korean flounder fishery. More and more commercial fishers are selling their boats to become aquafarmers or turning them to charter or head boats for recreational fishing.
Even though Korea is the most (1st) seafood consumption country per capita in the world; 58.4 kg , 63% of seafood consumed is from farming. Along with the other top consumption countries; Norway-53.3 kg, Japan-50.2 Kg, China-39.5 kg (US is 23.7 kg in comparison), the country is farming - including in the process of developing or importing, almost all highly demanded fish species. That saved most fisheries that were in serious destruction modes because of increased demands in 80's and 90's. It started with making of the its own national government dept.; the dept. of oceans and fisheries, separating from the dept. of agriculture and aquaculture.
I agree with you totally that much bigger harms in declining US fisheries come from commercial fishing. The industry rely too much on bottom dredging and trawling that destructs ecosystem; too much bycatches that are wasted and removed from the food chain. More importantly, it destructs habitats of the ocean floor and wipes out the natural water filters in oyster and clam beds. I was mesmerized by seeing how big and many trawling boats there were inside Point Judith Harbor, RI. Considering all the bottom and fish (in the name of target and bycatch species) those boats alone can destruct, I could believe the fishery was in deep sh...in US. Hopefully, people so the govt. will realize that soon, creating one system or rule to control and conserve the resource, because it is one ocean and the same fish whether caught recreationally or commercially.