Walleye populations across ND have shown for years that they DON'T need our help to thrive, so releasing fish to "Help" the population is a personal "Feel Good" that doesn't help or hurt fish stocks in any way. However, if you want to maximize the "Feel Good-ness" of releasing a walleye, then studies have shown that the 20-26 inch fish would do that. Female walleyes in this size range produce the largest percentage of viable eggs. Those 8+ pounders are grandmothers and have been shown to produce a substantially smaller percentage of viable eggs even though they individually produce a significantly larger number of eggs. I keep smaller fish just because I think they taste better and nothing more. If you want slot limits and closed spring spawning seasons MOVE TO MN or WI!!!! They have BOTH so you and ND will be much happier.