I've tried using the formula's for my (mostly steelhead) fishing and have found they usually exagerate the size of the fish. I wound up taking all the measurements of my hatchery fish one season and writing them down. I still write down the measurements of the biggies. Now I can look back at comparisons to actual weighed fish to estimate the size of those I release (natives). I think a seasoned fisherman can eyeball fish more accurately than using the formulas.

My 2 cents.
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If every fisherman would pick up one piece of trash, we'd have cleaner rivers and more access.