Can anyone tell me where to look to find out what kind of fish Nathan's uses... is it
HOki? I can't seem to find it on my own. Thank you.

Hi,
Looks like they use cod. Check out link.

Click here: Calories in Nathan's Famous - Fish Fillet Sandwich (http://caloriecount.about.com/calories-nathans-famous-fish-fillet-sandwich-i54206)