GOOD WEED: BAD WEED - Mike Gnatkowski

GOOD WEED: BAD WEED - Mike Gnatkowski


Walleye relate heavily to weeds during much of the year. Typically there’s a population that never leaves the weeds.


Weed is a topic of discussion across the United States these days as more and more states legalize or decriminalize the use of marijuana. Dispensaries are popping up on corners like convenience stores and you can drive though and pick up a bag of weed almost as easy as getting a Big Mac. 

Weeds, not the kind the country is now using for medicinal purposes, are a topic of discussion among serious anglers these days, too. Aquatic weeds are the foundation of the ecosystem in many bodies of water. As weeds go so do aquatic insects, baitfish and ultimately predators. A lack of weeds produces a relatively sterile environment and lakes that are commonly referred to as oligotrophic- “lakes characterized by a low accumulation of dissolved nutrient salts, supporting but a sparse growth of algae and other organisms, and having a high oxygen content owing to the low organic content.”

Weeds act as a filter to help to trap effluent, fertilizers and pollutants. Without them those things end up in the water. Fertilizers, nutrients and pollutants that leach into the water cause eutrophication—“a process by which pollution from such sources as sewage effluent or leachate from fertilized fields causes a lake, pond, or fen to become overrich in organic and mineral nutrients, so that algae and cyanobacteria grow rapidly and deplete the oxygen supply.” 

In between are lakes that are termed mesotrophic—“lakes containing moderate amounts of nutrients, and contain healthy, diverse populations of aquatic plants, algae, and fish. Occasional algae blooms may occur. If the lake is deep enough to stratify, a well–defined thermocline can develop during the summer months.” Mesotrophic lakes are typically some of the best fishing lakes. 

Lakeside property owners, in general, don’t like weeds. They want to have nice, clean pristine beaches so they can watch the grandkids frolic and swim in the water while reclining on their lush green lawns and patios. At the same time, they want to take the pontoon out and have those same grandkids catch a bunch of fish. It doesn’t work that way. 

Too many weeds, especially if it’s bad weed, can stifle a fishery. Like aspiring pot distributors, anglers who learn to recognize the difference between good weed and bad weed are going to be way ahead of the game. 

“Weeds are important,” claimed Michigan Department of Natural Resources Fisheries Biologist Mark Tonello, “but they can be a negative, too. They’re important because juvenile fish hide in them, but if they get too thick predators can’t effectively cull the population. A healthy plant community is critical for a healthy lake community.”

Weed control takes a couple of forms. Mechanical rakes are one way to eliminate weeds. Another much more common method is chemical treatment to eradicate weeds. Weeds are treated with a slurry of chemicals that can include copper sulfate, chelated copper, 2,4-D (which even sounds scary!) adjuvant, diquat, endothal, fluridone, glyphoasate and triclopyr. In Michigan, permits to chemically treat lakes are issued by the Michigan Department of Environment, Great Lakes, and Energy ( taking into account fisheries-based comments provided by the Michigan Department of Natural Resources. 

“We (MDNR) generally recommend leaving native species alone, but we do recommend the treatment of milfoil,” said Tonello. “We’re basically stuck with it. There’s some good that comes from it (milfoil), but it becomes a problem when there’s too much.” 


Too many weeds, especially if it’s bad weed, can stifle a fishery.


According to the EGLE web site “Program staff regulate the use of pesticides through the permit process. Each application for a permit must undergo a thorough review to assess the environmental impact to the water body, and any human health and safety issues.” How thorough the process works these days during the covid pandemic and manpower limitations is up for debate. 

Generally, chemical treatments do not take place over an entire lake’s surface, but mainly target the shallows. There are exceptions. The chemicals are deemed safe for wildlife and fish, but the problem, or the intent, is the chemicals kill the weeds. As the weeds die, turn brown and decay the oxygen levels in the shallows plummet. It’s common knowledge that many young-of-the-year game fish and baitfish spend a great deal of time in the shallows in the weeds. With perilous oxygen levels and degraded habitat fish populations may suffer for years to come.

Michigan’s Houghton Lake is a good example how treatment of weeds in a lake can go astray. In 2002 the lake property owners association convinced the powers that be the entire lake should be treated for weeds. The treatment killed all the weeds. Fishing success skyrocketed for a few years after that. With nowhere to hide baitfish and panfish were vulnerable and predators, and anglers, had a field day. 

Then reality set in. Once several year classes of predators were cropped or eliminated fishing success plummeted. With the weeds eradicated there was nowhere for panfish and baitfish to hide or reproduce and the insects and invertebrates that thrived in the weeds were gone. Once famous for its wild rice beds and the waterfowl it attracted, the wild rice has all but disappeared from Houghton Lake. Part of the reason for the disappearance of the wild rice could have been higher water levels we’ve experienced in recent years. Fishing followed a similar scenario. There are those that contend the fishery there has never fully recovered. Spot treatments are still conducted on Houghton Lake when problem areas are identified or invasive exotics get out of hand. 

“Weeds are a critical component in any good fishery, especially in a place like Houghton Lake,” said veteran angler Jeff Sowa. “A place like Houghton Lake doesn’t have much in the way of structure so weeds become structure. Baitfish take refuge deep in the weeds, panfish will tuck into the weeds for safety and predators patrol the edges. If you’re not fishing on the edge of the weeds, you’re not going to catch very many fish.” 

“Take big bluegills for instance,” said Sowa. “You’re not going to find big bluegills very far from the weeds except for a short period of time in the morning and the late evening when they move out to feed. Otherwise, they’re going to be tucked back in the weeds where predators or anglers can’t get at them.” 

Whether weeds are good or bad depends on their configuration or structure, their abundance and whether they’re native or invasive specie. Take milfoil for example. A native specie, Northern milfoil is good if kept under control. With its whorled leaves perched at intervals along it entire length that gives it a feathery appearance, Northern milfoil is a desirable specie that unfortunately will hybridize with invasive Eurasian milfoil. Milfoil can be positive habitat for fish, but it’s usually not long before the aggressive Eurasian milfoil dominates to the point of becoming too thick and control is warranted. 


Pike use weeds as both ambush points and edges to hunt along.


It would seem native plants with broad leaves provide the most benefit to fish. Affectionately known generically as cabbage by walleye anglers, members of the genus Potomogeton are usually good indicators of a healthy fishery. Plants like Richardson’s pondweed, American pondweed and large-leaf pondweed provide overhead protection and habitat through the entire water column. Panfish in particular will suspend in the vegetation using the leaves as cover. Largemouth bass love the security of overhead cover afforded by emergent vegetation. Schools of walleye can be found patrolling edges and openings in the weeds. Pike will take up strategic ambush points in the broad-leaf weeds or cruise the perimeter. 

Most anglers know what coontail looks like and associate it with a good spot to fish. A desirable aquatic plant until unruly growths around shore become problematic, coontail lacks true roots and can be found floating near the surface. Coontail differs from milfoil by its forked, non-feathery leaves. 

Elodea is similar looking to coontail and equally desirable as fish habitat. The propensity for its leaves to be thick near its growth tips and thinner towards the bottom makes it easy for fish to move through and yet provides cover from above. Species like pike, walleye, crappies, bluegills, sunfish, and perch favor submergent vegetation to take up refuge in and hunt. Bulrush and wild celery are thought to provide prime spawning habitat for a number of species including smallmouth bass and bluegills. One notable exception is the plant-like algae starry stonewort. Similar to native chara, this invasive quickly out competes its submerged rivals and destroys critical fish spawning habitat. 

Finding a diversity of plant life is better than one homogenous swath of vegetation. Places where a diversity of weeds exists produces various heights and density of weeds that attract more fish. 

There aren’t very many positives regarding invasive aquatic plant species when it comes to fish. Common reed or phragmites and purple loosestrife overwhelm native cattails. Although similar in structure to other members of the Potomogeton genus, the exotic Curlyleaf pondweed has a propensity for massive summer die-offs that dramatically lower oxygen levels triggering fish kills. 

One thing to remember is that green weeds are healthy weeds. This is particularly important when ice fishing. An underwater camera can be an invaluable tool for locating green weeds under the ice. Locating green oxygen-producing vegetation is critical for success anytime during the year. 

Once you find healthy weeds in open water there are three way to fish weeds- over, in or along them. “Walleye fishermen need to talk to bass fishermen about fishing weeds,” declared Jeff Sowa. “Bass fishermen know how to fish weeds.” 

Largemouth bass love weeds. Smallmouth bass use weeds to a lesser extent. Largemouths spawn before the panfish do and after guarding their nests retreat to newly emergent vegetation where they spend the bulk of the summer. In every lake that has walleye in it there’s a component of the population that never leaves the weeds. 

Bass zealots have a whole arsenal to pick from when fishing on top of the weeds. Rats, frogs and buzzbaits can skim right over the top of weeds without fear of getting snagged. Plastics, rigged to be fished weed less, are death on predators taking up residence in the jungle. Many a bass anglers has been surprised by a 6-pound walleye that inhaled their fluke or whacky worm. Drop-shot rigs plopped in holes in the weeds are likely to catch a hodgepodge of species depending what you have on for bait. 


Smallmouth bass don’t relate to weeds as readily as largemouth bass do, but you can find smallies near deep-water weeds known as cabbage.


One of the best tools for targeting weeds is a slip bobber. With its vertical presentation slip bobbers are a perfect weed presentation. “A lot of times with a slip bobber it’s a wait-and-see game,” claimed Jeff Sowa. “I think a lot of times you cast a slip bobber and a leech into a hole in the weeds and a school of walleyes will immediately come over to investigate. They may not want to eat it initially, but they don’t want their buddy to get it either. The first time you move the bait someone commits.” 

When the wind is blowing is a good time to fish on top of the weeds. Fish, like walleyes, will often position just above the weeds, especially on windy days. Ideally, the fish are positioned 6 to 8 feet below the surface. It’s a simple matter then to set up a drift using a live bait rig or crawler harness. The technique is often referred to as slick-rigging. Adding a bullet-shaped weight will help the rig pull through weeds they make contact with. Using smaller No. 8 hooks and burying the hook’s tip in a crawler will help make it more weed less and hook the odd jumbo bluegill you’re bound to run into. Leeches are a go-to live bait then, too. By using braid for your mainline, a jerk or snap will usually clear any weeds from your line. 

“From my experience 13 to 15 feet is a magic depth for walleyes wherever you fish and it’s no coincidence that’s right where the weed line ends in most lakes,” said Sowa. “It’s also where you’re going to see a temperature change at depth. It’s no wonder you see fish concentrate there.” 

You can troll or cast to work the outside weed edge. Look for points or indentations, cups or irregularities in the weeds and their composition to concentrate fish. You can troll the edge using crawler harnesses if pursuing walleyes or use a more passive approach with slip bobbers. Casting crankbaits parallel to the weed line is likely to produce a potpourri of bass, walleye and pike. 

To locate the magic edge use your side scanning electronics, underwater camera and your eyes with the aid of polarized glasses.

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