I have been told that the waters of Georgia Straight contain several hundred thousand seals. That does not seem an unreasonable estimate. Seals spend their time frolicking, sleeping, and eating fish. They are not careful eaters. Seals will typically take a bite out of a large fish and eat what they bit off at leisure, letting the rest of the carcass sink.
Seals are fairly biggish animals.
Many of them must weigh 50kg, easy. I haven't done a study of this, but I suggest that each seal has got to kill at least half a dozen fish each day. This suggests that each year seals eat around five hundred million fish in Georgia Straight. Let's assume that each fish weights 2 kg. We now have in order of 1 million tons of fish to feed the seals.