Its about energy conversion... Its takes about 10 lbs of prey fish to make 1 lb of LMB. So if your 5 LMB is eating a 1/2 lb LMB, it took 5 lbs of BG to make that 1/2 LMB. So your LMB is only getting 1/2 of food that took 5 lbs of BG to make it...