As is the case with many (most) salmonids, the length of the mouth is a good indication of sex. With females, the "fork" of the jaw (the point where the mandible and maxillary intersect) is usually at a point in front of or directly below the eye. In males the fork is usually behind the eye. In some cases, the jaws of the male are so long as to give rise to the nickname "alligators".
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PS