No one knows how many salmon a seal will kill, like wolves, they kill for sport, but it's pretty clear that each female salmon lays from 2000 to 5000 eggs. Apparently biologists don't take math courses in college.
Browsing around, only about 15% of eggs ultimately produce free-swimming young salmon, so figure 300 to 750 young salmon going downstream per female. Out at sea the survival rate to adult is about one half of 1% such that even without the sea lions the salmon were operating at onliy about replacement-level fertility.
