Did walleye stocking on an inland lake help grow its yellow perch population? Do changing water levels alter fish movement? Are more salmon returning to home waters?

Finding answers to questions like those is a big part of why the Michigan Department of Natural Resources does fisheries surveys — and, in fact, conducted more than 230 such surveys last year alone.

In 2019, staff from eight DNR fisheries management units completed 132 surveys of inland lakes and 101 stream surveys. Anyone fishing those waters might have seen crews collecting key data on state fisheries. So just what are crews looking for?

According to Randy Claramunt, Lake Huron Basin coordinator, surveys fall into three categories:

∫ Evaluating management actions.

∫ Understanding status and trends.

∫ Finding answers to new questions or concerns.

“Each management unit is responsible for determining if actions like fish stocking or habitat improvement projects had the desired effect,” Claramunt said. “For example, last year, the DNR stocked more than 21 million fish across Michigan. Surveys help us evaluate whether stocking resulted in better recreational fishing in certain areas or improved a lake’s overall health.”

Other annual surveys help managers track the status and trends of fish communities and important aquatic habitat on different lakes, providing a picture of those lakes geographically and over time.

Claramunt said streams throughout the state are handled a little differently, through two types of status and trends surveys: fixed sites and random sites.

“At fixed sites, we annually estimate fish population abundance — usually trout in coldwater streams and smallmouth bass in warmer waters — on a three-year rotation, while random site surveys are intended to give a species snapshot and show relative abundance,” he said. “We collect in-stream habitat data at all our status and trends sites.”

Fisheries managers use that third category, discretionary surveys, to answer questions or address current concerns, perhaps something raised by a local biologist, an angling group, or a lake association. Such surveys might be conducted to assess habitat suitability for a threatened and endangered fish species.

No matter the type of survey, DNR fisheries managers use the resulting information to strategize their actions, detect early indicators of invasive species, recognize developing threats to fish and habitat health, and much more.