Never managed to catch them, when they first arrived.
The Stubby Sharks are actually Wizard101 Birthday fish. If they come back, it'd be in September for Wizard101's 9th birthday. KingsIsle has brought back the birthday Gobblerfish every year, so I assume they'd do the same with the sharks. :)
Thank you for the response. I was fishing in Avalon yesterday and caught a Stubby fire shark. Concluded that it must be a 'shark week' thing and went to Triton Ave and caught the Warhammerhead shark! So shark week and stubby sharks are confirmed.