Can't see the definitive features on the inside of the lower jaw.... BUT...

No self-respecting chinook has an anal fin shaped like that! Neither does a steelhead.

The leading edge of a chinook anal fin is SHORTER than the base.

The leading edge of a steelhead anal fin is LONGER than the base.

Look at this pic to see the difference.

click here

Chinook anal fin = short and broad-based, trailing edge oblique to the body line.
Steelhead anal fin = long and narrow-based, trailing edge nearly perpendicular to the body line

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Based on the anal fin and the gross scale loss, one can only conclude it's a coho.

I think the most puzzling feature is the lack of a protruding ovipositor on a coho hen returning this late.... unless of course the "Curtis H factor" is at work here. My gut feeling is that the pic is legit (trees are completely barren of leaves).
_________________________
"Let every angler who loves to fish think what it would mean to him to find the fish were gone." (Zane Grey)

"If you don't kill them, they will spawn." (Carcassman)


The Keen Eye MD
Long Live the Kings!