Anecdotal evidence: My grandfather is a hobby fisher on the north sea. 15-20 years ago, he used to return with 10-20 eels after a fishing trip. Nowadays, it is usually 1-3.
There used to be loads of eels to smoke, and even some smaller ones to just fry in a pan. Nowadays, every eel gets smoked, and there are not a lot of them. This experience is mirrored in that of all his fisher buddies, and i personally experienced that decline.