I shifted gears. I'm not talking about the same day, just overall during the season.
Yeah, so was I. I can't say I've ever verified catching the same fish in the same day. I have done it on different days, though, with pics to prove it. Spring, despite having caught more fish there than probably any other stream I've fished, I have never done it.
Quick calculation on Spring Creek. This is rough back of the envelope stuff.
Biomass - we'll use 150 kg/ha. It's higher in places and lower in others.
Average size of fish: We'll say 9 inches, which is about 0.3 lbs.
Average width: using 50 ft, based on scale marker on bing maps aerial view.
150 kg = 331 lbs = 1103 fish.
1 ha = 107,639 sq. ft.. At a width of 50 ft, this is 2152 ft in length (0.4 miles).
We get a little under 3000 fish per mile. Slightly better than 1 fish for every 2 ft of stream length.
Now, taking this further, I don't doubt that on the average day there's 40 or 50 anglers on Spring Creek. But not PER mile. Bottom of paradise (not including the project itself) down to the handicap ramp is about a mile of water, and one of the more popular stretches. Sure, it's higher during sulpher time, and lower during an ugly day in winter, but lets say, for the sake of argument, the year round average is 10 anglers fish this stretch per day, and they each average catching 5 fish per outing.
That's 50 fish being caught daily out of around 3000 fish being present in that stretch. If that was kept up for 365 days straight, that's 18,250 trout caught. With about 3000 being present. i.e. the average fish gets caught around 6 times per year.
I don't doubt some of these assumptions are off a little. But it gives a decent ballpark, I think. In a stream with very high pressure, even with high biomass, the average fish gets caught multiple times per year. But not so often that they're being caught every other day or so, either.
It also speaks to tackle regulations. Lets say the mortality rate is about 2%. That's around 365 trout per year in this stretch alone, or about 12% of the total. If you doubled it, to 4%, now your losing nearly a quarter of your fish to mortality. Becoming significant. And you're killing half your population on a yearly basis at 8% mortality.
Those aren't crazy high mortality rates, and this is one of the most prolific trout populations in the state. It really speaks to what increased mortality can do on a highly pressured stream.