From Bill Cody in another post from last year:

Originally Posted By: Bill Cody
As usual it ALL DEPENDS. It depends on how big the FHM are. Huge numbers/lb if they are hatchlings not so many if they are old breeders, which in the north, in the spring, most sold are older fish of 2.2"-3" usually 250 to 150/lb depending on FHM length. Plan on 200-250 per lb. In the fall new crop FHM are usually somewhat smaller 1.7-2.2" and 350-250/lb.