I am NOT a Relative Weight guy, but these are my fishing observations.

A female LMB right before the spawn is at her largest RW of the year (obviously). The males right after they have been guarding the nest for an extended period may be at their skinniest for the year.

I am not positive that RW measurements taken at this time of year are necessarily indicative of the health of the bass population.

(All of the more knowledgeable people feel free to correct me or expand on this comment.)