Wow, I'd say about half of my Crocodilos today resulted in "lack of skill" messages. Using full fishing+ gear, Mega Moglification, Adv. Support, the works. I'm fishing them completely to 0% as well.
e: Will post stats in a few minutes; this is getting ridiculous. Unless they are significantly higher in level than liks/gugs, and are simply easier to wear down stamina-wise, I don't know what's going on. I certainly didn't get the "lack of skill" message more than ~5% of the time with liks/gugrus (although they also were apt to snap lines; crocs don't snap lines).
Ended up with 11 catches, and 10 "loss due to lack of skill." Again, all drained, and using full +fishing effects. In comparison, I successfully fished up 19/19 Pelazoea. Quite odd. Was also using "Master crafter" and "Ace angler" atmas if that makes any difference (it shouldn't at all, but I figured it fit the theme of fishing, so why not).