you really don't even need a measurement tool to figure it out. If the spines on the dorsal are perfectly straight, not mangled or curved, then chances are it's a native fish. I personally think that they should lower the height requirement to 1 and 3/4 or something similar. There have been a lot of native steelhead bonked within the national park due to that rule.
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Another patient exhibiting symptoms of the steelhead virus.