Some of the penninsula rivers have as a requirement the measuring of a steelhead's dorsal fin to tell if it is of hatchery origin or not. The national park regs note a dorsal height of less than 2 1/8 " (credit card width) as a hatchery fish.

I have always measured the rear of the dorsal from the back to the tip of the fin with the fin AT REST. A friend disagrees, saying the fin must be fully extended and THEN measured.

The regs make no mention of extending the fin before measuring so who's right?