A 31" walleye is defiantly a trophy and when she recuperates, she would easily go 10#+. I have been walleye fishing ever since I caught my first one in 1980 while ice fishing for crappie and caught a 29 1/2" and 9 1/2# and i was hooked for life and I've caught lots of 30"+ eyes over the years starting when we moved to the central basin sometime around the end of the 80s. most summertime fish over 30" will weigh over 10#. In my experience a walleye weighs a # for every inch of length. a 24" will be close to 4# and a 29" fish will be close to 9# and a 32" fish will be around 12" but this doesn't apply to big females full of eggs in the spring.