The Simple History of Submerged Wood in Our Northwood Waters

We as humans have always viewed nature from the oral and written history of our ancestors. Do you think that now we can view what we know of natural history and apply our knowledge of modern ecology? Let us use our northern forest and lakes as example. Let us walk through this history as we know it and see if we can take the messages, it offers and apply it to today.

Our pristine Northern lakes are so tied to the forest around them both aesthetically and biologically. The nutrients in the lakes and waterways slowly accumulated as the glaciers retreated 12 to 15,000 years ago as the forest developed alongside of them. We tend to look at our lake and their watersheds as a history that began with the logging old growth forest during European settlement as this is written down. A newer perspective of history in that of Native Americans who look to the same written history but look beyond it at their traditional oral histories. All is good but we must squint our eyes look even deeper into Northwoods.

In 1859 a German published a book, Jóhann Georg Kohl, called KITCHI-GAMI  A Life Among the Lake Superior Ojibwa. It is a description of his living among the Ojibwa in 1955 and his travels to other tribal communities. He traveled to Lac Du Flambeau and gave a description of canoeing through Torch Lake and the primeval forest.

“The entire lake was framed by dense primeval forest. Here and there an arm branched off, and was lost in other dense forest. At some places the forest marched like hostile battalions, with leveled bayonets, against each other, narrowing the lake to a river, while at others it was a mirrored blue expanse.” (Page 175)

Hemlocks, black spruce, white cedar, and tamarack historically lined the shores of our northern lakes, supplying woody debris that initially accumulated along lake margins before being transported by ice or floating into open waters. This process occurred well before the upland areas of pine and hardwoods were subjected to logging … and well before humans had any impactful effects on the natural ecology.

This era of logging used many of these same lakes and waterways to transport logs, damming many of them submerging these shoreline species and further contributing woody debris to the lakes.  Woody debris on the shoreline and in deep-water was habitat for fish and aquatic organisms was the norm for thousands of years before this. Woody debris continued to add nutrients to these pristine waters.

So now to the point of our fisheries and their relationship with woody debris. Fisheries research in Wisconsin is just beginning study of importance of woody debris as cover for fish and other organisms along shorelines on an undeveloped lake. This has been prompted by the expected decline of woody debris along shoreline due to the proliferation of  shoreline development (where are the bass hiding on a summer day, ask any bass fisher …under a dock!). To counter this development in lakes, government regulators recently have reacted to this decline and produce a guide and permitting system regarding the placement of “fish sticks” that cable clusters of trees to the shoreline. Funding can accompany their placement but carries a bigger stick to be tied to restoration of the shore itself with a mandatory 10-year preservation clause.

Let us move on to search for woody debris in deeper waters. For over 75 years, fish shelters called crib – hardwood timber stacked like cabin logs – have provided habitat for both large and small fish if the tree top brush inside remained intact. These cribs were built in winter on top of the ice. These cribs were often randomly placed, drifting to their final location as ice melted. However, they sometimes became navigational hazards.  They were dubbed as “fish coffins” by fish biologist as anglers often targeted and caught fish living within them. But they indeed are both cover and food for all sizes of fish in all seasons if the brush is maintained in them.

What if we look fish and aquatic cover in deeper waters? Where would it most benefit  fish and aquatic organisms? Where does a human fisher find fish in summer? It is at the thermocline where temperatures are the coolest and oxygen levels the highest. Fish biologist as well as informed fisher know that all fish are keen to finding the right temperature and most oxygen seasonally, but it is most important for larger fish in summer that have trouble meeting nutritional needs for any growth and their everyday metabolic needs.

What does deep water cover at the thermocline do for fish the rest of the year? Survival of emerging post larval fingerlings from the shallows must reach the zooplankton found in deep water as the lake mixes in spring at turnover and begins to warm. This later thermocline cover of summer is now cover for these fish even before the summer thermocline.

Fish that spawn in early May such as muskellunge, northern pike, walleye, yellow perch and white sucker all need the zooplankton found about the third week in May. This is the first weak plankton blooming after ice is out when the water warms and the nutrients are available. The second strongest zooplankton bloom in late June is utilized by late May and early June post larval fingerlings of bass, bluegill, pumpkinseed, rock bass, and rock bass. Black Crappies are in the mix feeding on all.

Research indicates that young walleyes (Age 0) are not surviving past the early weeks of July to recruit into the adult populations later in life. Studies also show that, in Northwood lakes, yellow perch become the primary food source for walleye after both species transition from zooplankton. Ecological observations suggest that woody cover near deep water provides potential benefits for all post-larval species.

Once again, we must look back to times before humans disrupted what nature has figured out by once providing an abundance of aquatic life. We can do no better than that in today’s management of our lakes and fisheries.