Same reason this happened to oysters. Turn of the century industrial pollution made good oysters rare. Same with lobsters... and to a lesser extent Atlantic cod... although cod fisheries were destroyed by over fishing.

Prices spiked, making it hard for peasants to get. This exclusivity attracted the wealthy. And here we are today. EDIT: As others mention "cheap" refrigeration came into play, but 'friges and ice boxes were around by very early 19th century. This is the reason "salt cod" was such a popular protein source for centuries and because they were so easy to catch, the fisheries were literally destroyed.

Fisheries have since recovered for lobster and certain oyster species and their prices reflect this change. Decent logistics and just-in-time supply chains further reduce cost and deliver live catch. And yet, Atlantic cod may never fully recover.

Also note, production and value are not necessarily the same thing. Canada leads the world in lobster production, but Maine leads in value. Louisiana leads in oyster production, but Connecticut leads in value.