Sorry Ike, but it isn't Salmo that needs to check their arithmetic. You are off by a factor of 100. Where you say that a return rate of .01% would have returned 5000 fish, it actually would have returned only 50 fish. Why? Because .01% = .0001, so multiple roughly 500,000 smolts x .0001 and you get 50, not 5000.

Put another way, your calculation of the return rate is also off by a factor of 100:

112 returns divided by 486,767 releases = .00023 but to turn that into a percentage you multiple by 100. That makes your estimated return rate .023%, 2.3 times what Salmo suggested.