July 2010

The DNR communications team works with agency experts to develop the weekly questions and provide the answers. This feature addresses current DNR issues, interesting topics, or the most frequently asked questions from around Minnesota.





With slot limits on nearly every Minnesota lake it is important for anglers to know the fish they keep are of legal size. What is the proper way to measure a fish?

An accurate measurement of an angler’s catch may be difficult for a number of reasons. The boat may be pitching and rolling on the lake. Fish are slippery creatures that do not like to lay still. Also, there are many obstacles in the boat like hooks, tackle boxes and other anglers. However, accurately measuring any fish caught helps sustain fish populations and evens the playing field for all anglers. And of course, an accurate measurement is necessary to comply with slot limit regulations.

To properly measure a fish, anglers should use a rigid ruler affixed to a flat surface with an "end stop" at the zero end. Lay the fish over the ruler with the nose pressed against the end stop. Pinch the tips of the tail together. The length of the fish from nose to the tip of the tail is considered the legal length of the fish. While in rough water, the end stop acts as a measurement aid, preventing the fish from sliding around on the ruler.

Flexible tape measures or rubber rulers do not provide an accurate length. In addition, measuring “stickers” should not be used because they can shrink in the sun. A metal or plastic measuring device is best.

- Maj. Rodmen Smith - DNR Division of Enforcement operations manager


Finding a place to ride an all-terrain vehicle or other off-highway vehicle (OHV) in Minnesota takes a little research. Are there different levels of riding opportunities throughout the state – from novice to adventurous? And how can riders find the trail that fits their needs?

Minnesota is using the standard symbols to identify level of difficulty. The symbols are: green circle – easy; blue square – moderate; and black diamond – technical or advanced. Most public OHV trails are green, with some blue levels available.

The Red Dot and Spider Lake systems are two sites that have some blue level trails. At this point, the only public riding area with black diamond level opportunities is the Iron Range OHV Recreation Area in Gilbert.

It is important for riders to know their abilities and know their machines. Most of these trails do not provide alternative routes – once the course is started, it must be finished. The more advance trails are generally one way as well.

-- Mary Straka, DNR OHV coordinator


Devices that roll weeds have become popular tools for eliminating unwanted vegetation along the shoreline. What sort of problems do they cause for fish and water quality?

Mechanical devices that roll weeds are commonly used to control aquatic vegetation in public waters. Their use is regulated by the Minnesota Department of Natural Resources (DNR) through the issuance of permits. Not all sites are suitable for the operation of these devices, however. Although they can be an effective method of controlling vegetation, these machines can have a negative impact on lakes, which is an area of concern when it comes to lake management.

The potentially harmful effects of the loss of aquatic plants are felt by a wide variety of species, including waterfowl, invertebrates, amphibians and fish. Specifically, devices that roll weeds can decrease water clarity by displacing sediment, and destroy fish spawning beds and nursery areas. This can potentially impact recreational activities. Lakeshore owners should be aware of these tradeoffs when thinking about using such devices.

A permit is required and should be obtained before using any mechanical vegetation removal device.

- Wayne Mueller, DNR aquatic plant specialist


DNR Question of the Week Archive