When that rule was a state regulation in 1984, the measurement was made with the dorsal fin extended. That's the only way that makes sense to me. "At rest" could yield several conflicting measurements, making such a rule useless, not that I'm saying such a rule is perfectly useful, either. But it's more enforceable, that is, the fin either measures 2 1/8" or it doesn't, as opposed to the more subjective interpretation of when is a fin a stubbed dorsal fin or not. I think the subjective interpretation could easily be in the high 90s percent accurate, but it's less effective as an enforcement rule. I presume that's why the NPS chose the credit card rule.

Sincerely,

Salmo g.