My pet peeve with fish.. or the LFS's is how ten names get thrown on the same fish, even with scientific names, a species may or may not go about a variety of them, of course this depends on who you ask.
Anyway's I've never heard of this Blue Dolphin Shark, however if you say it's looke similiar to an Iridescent Shark
Try searches on
Pangasius Catfish
Pangasius Pangasius
Paroon Sharks
Black-Fin Sharks/Columbian Shark
Berney's Shark Catfish/Australian Shark Catfish
Lots, and I mean lots of catfish are out there, that somewhat resemble "marine" sharks. Most of these kinds of fish, outgrow home aquariums, however some are be able to kept in 100 gallon tanks or less.
Also a note about the Paroon Shark(which I think looks most like a shark out all catfish during it's subadult stage), if that turns out to be your interesting looking catfish, the common Pangasius sanitswongi, they get huge, some say anywhere from 3-6 feet. However, some people also there's smaller very very similiar subspecies. Planet Catfish said there's been a smaller hybrid of the Paroon Shark in order (well they said artificial) to keep down it's low size and keep it's attracting looks. None of these I can seem to get confirmed, so who knows. I've included some pictures of these guys, as junveniles, very small adults.
Good places to look:
Here at AquariaCentral.Com Check out some of the species profiles of the above catfish.
Planetcatfish.com has a good resource and picture library.
Scotcat.com is also good, but I find there site kind of hard to navigate, but still very good.
Hopefully this will help you find what your looking for.
