You don't want them to eat right away. They still have some of the yolk sac to absorb internally. It could take a week of so for them to use all that.
After that, start with small foods that are really oily/smelly for them.
shark is doin good swiming around now survived the move in the below zero temps we have here and about to move again seeing as the fiance threw me out on my ***
Any update? Ours (same kind of shark) ate after about four days. We started with PE mysis shrimp - had to stick it directly under its face. Soon he started getting more pro-active about swimming after food, then we started giving him krill and scallops. He chases these down now and sucks em in like a hoover. So fascinating. I hope yours is eating or will soon!