Macrophyte Mastery

Welcome to the Jungle

Submerged vegetation fuels bluegill and crappie patterns like an elixir, even during seemingly sterile winters. Although plant biomass decreases significantly as ice builds, in many lakes—particularly the clearer ones—certain evergreen plants continue to photosynthesize oxygen throughout the cold months.

Although we’re talking mainly from an ice-fishing perspective here, aquatic plants undergo similar winter cycles in climates where lakes experience cold winters but don’t necessarily freeze up. So these patterns often apply to anglers fishing open waters during the colder periods.

Science tells us that at early- and late-ice, all through winter if snow cover is negligible, sunlight feeds rooted plants, at least intermittently. Despite this, dissolved oxygen (DO) levels in shallow zones continue to erode throughout winter because of decomposition. In milder winters, however, DO replacement via plant photosynthesis can be enough to sustain life. Panfish, in these cases, potentially feed and hold in these littoral zones all winter.

Opposite conditions, on the other hand—turbid water, deep ice, and snow—reduce sunlight penetration and oxygen production by plants, and decomposition depletes DO at an accelerated rate. Eventually, bluegills and crappies fade from flats and reassemble in deep basin holes, where large groups band together. Anoxic conditions can prohibit longterm fish survival, yet we can’t say for certain that all littoral flats lack bearable oxygen levels, as anglers have no simple way to measure oxygen.

We know that panfish, like other species, venture into low-tolerance zones if these areas harbor abundant forage. Some invertebrates eaten by panfish, particularly chironomid midge larvae, thrive in low-oxygen environments outside fish comfort levels, yet these “bloodworms” frequently pack panfish stomachs tight. The same for shallow, decaying weeds that provide food for backswimmers, water boatmen, and certain microcrustaceans. Bluegills love foraging on these critters, even though in winter they often cling to decomposing plants.

Some shallow, weedy flats offer sufficient DO (roughly 6 parts per million and greater) all winter. This is true more often than anglers suspect, even during late-ice. Certain key species of winter-hardy plants continue adding oxygen throughout winter. Groundwater streams percolate through the substrate, creating oxygen-rich microhabitats. Such microhabitats consist of a bubble of highly oxygenated water—a capsule of life in hostile surroundings, an oasis of vegetation with invertebrates and fish packed into a finite area.

Clearly, the well-worn line about green weeds luring flocks of hungry panfish isn’t as simple as it seems. Still, given a little plant knowledge, the process begins to make sense. Some plants wither in fall, some crumple in summer; others, given the right water conditions, remain evergreen throughout winter, continuously producing oxygen. Some of these evergreens actually appear more brown than green.

Finding stands of live plants is a tricky business until you get comfortable with plant identification and corresponding habitat. It requires inspecting the terrain in search of certain species of plants, rather than trying to arbitrarily determine which ones on a weedflat remain alive. Lots of the searching today involves an underwater camera, such as an Aqua-Vu.

Plant vitality can’t always be determined without pulling a strand through a hole, and even then, it can still take a botanist to make the call. Even a seemingly upright stalk of something like pondweed isn’t necessarily photosynthesizing. Until anglers regularly employ and interpret DO meters, camera work remains the best way to help us make judgments about where to fish.