SPIRIT LAKE — For the past 21 years, every walleye caught during the April gillnetting season at the Iowa Great Lakes received a unique alpha numeric tag, gave up a spine and was measured before heading back to the cool water from which it came.

That information has been feeding a database now stretching 24,000 walleyes strong and is being used to keep track of the health of one of the most important populations used for Iowa’s fish culture program.

The Iowa Great Lakes walleye population supports the Spirit Lake hatchery with eggs to produce more than 67 million fry that are eventually stocked into lakes and streams across the state. The database tracks annual abundance, survival and growth rates of those walleyes and is used to support additional research projects aimed at improving walleye fisheries across the state.

Jonathan Meerbeek, natural lakes research biologist for the Iowa Department of Natural Resources, took over the study in 2010.