The $5 harvest tags, which can be purchased at any DNR Electronic Licensing System agent, are used to collect information on the statewide lake sturgeon harvest, which runs April 24 to May 7. Anglers who practice catch-and-release do not need a tag.
For further information check link listed below.
http://news.dnr.state.mn.us/index.php/2008/04/01/early-canada-minnesota-lake-sturgeon-harvest-season-opens-april-24/#more-42306