yeah, definitely Acestrorhyncus spp... They definitely CAN be weened to frozen smelt (whole is easiest). I had one for a couple years, got him to about 9" and then he got eaten by something else in my tank.
THey are peaceful, not tough fish, but will eat ANYTHING up to about 2/3 their own size (and may try even larger). THey are brutally effective and fast piscivores. Lightning speed.
Don't put them with anything "tough" that might bully them (they can't defend themselves" and don't put them with anything small enough to get eaten.
Do great in a pack of several fish... the more the merrier, but they need SPACE as they do swim FAST! Minimum 180 gal.. not because they are big, but because they need the space for swimming .
Bigger tank would be much better.
Finally, they way I got mine off feeders: Started with feeders. Dropped them in tank ONE AT A TIME. Feed once per day. AT SAME TIME EVERY DAY. So fish got used to knowing when the lid opens at 9pm, feeder is getting dropped in. Then, started doing it with DEAD feeders. So the fish because trained to wait for feeding , and hit AS SOON AS the feeder hit the water.
Then, within a couple weeks, I stopped using feders and used whole smelt (small)... also called SILVERSIDES when you buy them frozen at LFS.. but they are cheaper from asian market. $1.49/lb. I would thaw them slightly first, so they were not hard, then drop them in... and BAM...