I made usually around 120 to 150 millions in 10 to 12 hours fishing in either Kama or Oquilla and selling the stuff to the trade in Valencia, but now I rearly get over 60 to 70 million. 

My guess is the catch rate for yellow and red fishes was lowered, but maybe there was a change with fish prices too.

Anybody experiencing the same thing? 

Yes, they made a stealth nerf to fishing. You don't get a bite for like 20 minutes, then you "catch" 6x Plump Coelcanth OR one of the 3 million silver event fish.

Overall nerf and completly STOPPED leveling both fishing, and trading by selling the fish, becuase you only catch non-tradable event fish now, from Velia Beach.

That only applies to the event areas.  OP is asking about other areas.