My first question was don't we already know that or can extrapolate from previous papers ? Perhaps the researchers need something to do to justify their existence? Nice to do in such a controlled situation.
When you are able to download and read the paper, they will discuss a theoretical model called Equilibrium Yield. That theory predicted for Escanaba Lake ... that a 22 in Length limit would result in increased yield of NP. So the limit was expected to increase the harvest of NP per acre per year. The average however dropped from an average of 3.2 lbs/acre/year to only 0.9 lbs/acre/year. The DNR was wise to test the limit in only a few counties. These findings along with other very similar studies on length limits was altered fisheries management in the 1970s (think Richard Anderson and concepts around PSD and the control of populations through harvest in the QUALITY/STOCK lengths (2-3 years of age). DNRs have limited means to control populations to the betterment of yield other than length and bag limits. So much of what we have learned from Richardson and others about PSD is difficult to employ with bag and length limits.
