What size is the shark? If it's under about 8 inches then the pup was probably ripped out of a pregnant female and might not make it. This is just one opinion. Other things to look at would be if there is any electrical currents in the tank (can solve with grounding probe), was the tank ever treated with any medications (most are extremely harmful to sharks), or are the water parameters OK. Any one of the above could be an issue. Collection stress can cause long term problems that sharks can not get over. I'm sorry if I'm not of more help but if you could post the water parameters and some more info and I'll see if I can help you. Just to let you know I was a Biologist at the New Jersey State Aquarium for some time and was one of the people that cared for the sharks in the ocean tank, so I have some experience.