I have been fishing many hours this weekend in Baobab Crown in Zafaria to catch a Rhino and the Ecto Slime Skate. Whenever a storm fish appears and I cast, the line snaps. It shows ripples but not the "The fish got away" message. Every single storm fish has snapped the line. I have fished in Ivan, Kraken, Dworgn, and Diego realms. Some life fish have also snapped the line and I take that to be the EctoSlimeSkate as I sure can catch plenty of treants. I have even bought the major fishing luck elixir to see if that would help. It didn't. I also used a higher rank lure thinking perhaps the rhino was heavy. LOL That didn't help either. I could catch the Duckbill Eel in the Baobab Market within minutes and that's an epic fish so why is there trouble catching the Rhino and EctoSlimeSkate? All the fish that snap the line don't have the "It got away" message.
Are you sure it's not sentinels snapping the line? If sentinels are in a pond then they will swim to your bait quickly and break it. You need to complete the fishing quests in Dragonspyre and Avalon to obtain the Banish Sentinel's spell.
I did not see any sentinels in Baobab Crown. I know they are in other areas in Zafaria. I was staring at the water and fish. I know those sentinels are fast and I do have the banish sentinel spell. But thanks for thinking of that.