I can not document with anything on paper, but I have seen shrinkage in fish in a livewell. During a tourney fishing run in KS in the mid 90’s, we did have to on occasion toss back a short fish that was 18+ a fraction when it was put into the livewell. Stress, bouncing around a livewell, warmer surface water being circulated into a livewell may have been contributing factors. If you weighed a short fish you were DQ’d, so questionable fish were re-measured. We would even measure during the day, so if a fish came up short we could toss and try to catch one to replace that fish. On many occasions if you measure a fish on one side, then turn over it will be a different length, so if close, turn over. Also have the creel guys do same at the dock if you get checked with a shortie. Hope this .02 cents is worth something.