When you think of Michigan’s economy, the first thing you might think of is the auto industry, or logging, perhaps, if you live in the north. Maybe you think about Pure Michigan, tourism, and all the fun things to do in our great state, particularly fishing. Did you know that fishing contributes about four billion dollars annually to the State’s economy, provides close to 40,000 jobs, and more people travel to fish in our state than any other state except Florida?
Any Michigan resident can drive to a quality fishing hole in less than an hour. Some of us don’t even need to drive! What makes the fishing so great all over the State? Is it the fish stocking program? That’s helps when waters can’t produce fish on their own. Is it the clean water laws that are in place? They definitely are a big help. What about trees? Yes, the abundance of trees is actually a major contributor to quality fishing!
Forested lands in a watershed determine how water reaches rivers and in what quantity and quality. Forests also determine the water temperature, what physical shape the river will take, and the strength of the entire food web.
Higher percentages of forest within a watershed contributes to the stability and consistency of water flowing in streams. With healthy forests, you don’t get the “flashiness” (big peak floods), the low summer water flows, or the erosion that is common with watersheds characterized by agricultural or urban use.
Areas along lakes and streams are called riparian corridors. These areas have a direct influence on the water quality and habitat for aquatic life in the adjacent water body. Forested riparian stream corridors are critically important, especially for a trout stream. Optimal trout habitat is characterized by clear, cold water and relatively stable water flows and temperature regimes. The trees growing over the stream provide shade, keeping the stream water colder. Deciduous leaves falling into rivers also make up the base of most small stream foodwebs. Whole trees or branches that fall into the water help to physically shape a stream and provide a diversity of habitats.
Colder water temperatures maintain high levels of dissolved oxygen, which is a vital component for trout habitat. Colder water holds more dissolved oxygen than warmer water. Colder water temperatures also help fish maintain optimal metabolic rates and improve their resistance to pollution, parasites, and diseases. Trout often prefer waters 50 -60° F, but can handle water temperatures to about 72°F.
Leaf litter, or the deciduous leaves that fall into a stream, begin to slightly dissolve and quickly are colonized by algae and bacteria. These microbes are then fed on by aquatic invertebrates, which in turn feed several other parts of a stream foodweb. For the vast majority of small and medium-sized streams and rivers in temperate regions, it’s well documented that leaf litter inputs are the major driver of foodweb strength.
Entire trees or large branches that fall into lakes or streams are fundamentally important to the productivity of fisheries. Around lake shorelines, these fallen trees are preferred spawning cover by fish species like crappies and largemouth bass who use them for nest sites. Other lake species like northern pike, require undeveloped natural shoreline to spawn successfully. They don’t build nests, but need the protective shallow cover and structure of natural shoreline for success of their “broadcast” spawned eggs. In streams, fallen trees change the topography of the stream bottom. The water bends and swirls as it flows around and over the obstacles and digs into the bottom carving out deeper pools. Deep water spots and more complex habitats are essential to the survival of many fish species, and the different life stages of fish.
One of the more important roles a tree plays in the riparian corridor is that of a streambank anchor or stabilizer. Tree roots trap soil along the bank, reducing the amount of sediment released into the river. Excessive sedimentation causes a multitude of impacts to streams, and has long been considered by fisheries biologists as the number one pollutant of streams.
Trees also help regulate the amount of nutrients and sometimes pollution that is released into the stream. They slow the flow of surface runoff allowing it to soak into the soil, which slowly filters water before entering the stream. By contrast, consider how a paved city road during a rainstorm gathers oil, sand, and other litter as it flows to a drain.
So, what can you do to help keep Michigan fisheries healthy and strong? First, keep your forest in the family. Maintaining your land as forest rather than conversion to agricultural, residential, or urban land use is helping our waters. Second, use best management practices, or BMPs, when conducting forest management activities.
The Michigan BMP manual (Michigan.gov/PrivateForestLand) recommends a 100-foot Riparian Management Zone (RMZ) along bodies of water. That width can be reduced or increased based on the conditions of the area along the stream, but the general recommendation is there to signal that RMZs are places that need to be managed differently due to their critical importance to streams, lakes and wetlands.
Forests for Fish is a new program sharing the story of how forests support high quality fisheries and clean water. It is a collaboration with the DNR, U.S. Forest Service, Trout Unlimited, Michigan Tree Farm program, Michigan Association of Timbermen, and the Michigan Association of Consulting Foresters. Forests for Fish supports forestowners by providing cost-share to develop a Forest Stewardship Plan and by underwriting the cost for a professional forester to offer a free Tree Farm site visit. Trout Unlimited is developing materials to further explain the concepts described in this article and to provide guidance on how you can implement stream habitat improvement projects in your forest.
Trailer: Matt Modlin is a forester who is passionate about fish. He has a bachelor’s degree in finance from Michigan State University and a Master of Forestry degree from Michigan Tech. In his free time, he loves being outdoors fishing, camping, hiking, canoeing, photographing wildlife, and playing sports. Michigan Trout Unlimited is a non-profit organization with the mission to protect, conserve, and enhance Michigan’s coldwater fisheries and their watersheds. It has 20 local chapters around the State, and approximately 8,000 active members.