I release all walleye over 19″, whether the law requires me to do so or not. I do so on the rivers and reservoirs in SE Iowa where I have lived for five years now, even though there is little succesful natural reproduction of walleye in those waters. I do so because large walleye aren’t very good eating, which I know from experience when I was younger, and because those fish can grow larger and reach trophy size.
I lived in Winona for seven years, and saw quite a few big females kept, including some I kept when I was younger and didn’t know any better. I do think a lot of them are being released, which is a good thing. I also agree with those who say C and R of large walleye is becoming more popular, based on what I have seen and heard.
The MN-WI section of the Mississippi has a 15″ minimum size limit on walleye, which ensures that fish have a chance to reach sexual maturity before they are harvested. This is a great deal better than nothing.
The IA-IL section of the Mississippi down here has a 15″ minimum on walleye, along with a 20-27″ slot limit, which requires all walleye within it to be released. So far, that seems to be improving the walleye population down here, by all accounts. As someone else said, though, the Wisconsin DNR does not consider it necessary, and from what I hear neither does the Minnesota DNR. So, although I would like to see Minnesota and Wisconsin try it, I am not holding my breath on seeing a similar slot limit enacted anywhere between Dubuque and the Cities.
I am guessing that Minnesota’s new state-wide limit of only one walleye over 20″ per day does not apply on the MN-WI section of the Mississippi, which is too bad. Ironically, I don’t like the state-wide application of this slot limit. Most lakes in the Metro area and the southern third of Minnesota have little succesful natural reproduction of walleye, and so protecting large fish on them makes less sense to me, since I believe the best argument for a slot limit is boosting natural reproduction by protecting the large females. That is why I would like to see a slot on the Mississippi, where the walleye population is entirely self-sustaining.
And, there is no way to tell a male walleye from a female walleye if the fish is less than 18″ or so. Externally, male and female walleye are identical. Male walleye seldom grow to be over 18″, so it is safe to assume that all fish over that size are female. Females under 18″ or so have not yet reached sexual maturity, so the burden of spawning falls on mature females which in most waters are larger than that size.