Freshwater jewels

You’ve probably seen neon tetras, bleeding hearts, clownfish and yellow tangs in aquariums. In all likelihood a fish just as beautiful, or more so, swims in your lake.

For my money, no fish is prettier than the sunfish – officially the pumpkinseed. I sometimes question why they are named for something as nondescript as those off-white ovals pulled from Halloween jack-o-lanterns. But of course the name “sunfish” belongs to a family of fishes that include the bluegill. Still, what the experts call pumpkinseeds are always sunfish to me.

Bluegills are pretty fish in their own right, but they look pale next to sunfish: Those eyes with bright-red iris around the dark pupil. The wavy lines that radiate from the mouth across the gills, in a color like aquamarine charged by blacklight. The deep black gill spot with the accent of brilliant red. The subtle pattern of blue-and-emerald vertical bars across the golden body. And then that bright yellow-gold belly.

Years ago (and I’ll admit I did this illegally, without a permit) I kept a couple of sunfish in an aquarium – they looked great amid the green artificial weeds, lit by the fluorescent lamp, and our toddler daughter loved watching them.

Fortunately for us all, sunfish are extremely common. They’re generally not as abundant as their bluegill cousins, but you can find them in almost any lake. They live in the shallower water and in the weed beds, eating mostly insects and their larval forms. They prefer water temperatures in the low to mid-70s. They live up to 10 years and can grow to 8 or 9 inches, though you won’t often see specimens that size around here.

Sunfish are easy to catch. They’ll take almost any live bait – worms, grubs, crickets, small leeches – but also artificials like dry flies, poppers and small spinners. When fishing with kids, nothing will bring more cries of delight than one of these jewels, popped from the lake, multiple colors glistening in an evening sun.

Why can you see better into water with polarized glasses?

Many of us know we can discern more features in shallow lake water when wearing polarized sunglasses. It’s easier to see fish we want to catch, observe bottom features, or discover treasures like lost fishing lures with those glasses on. But how exactly do polarized lenses work?

They do it by filtering out reflected light. Light consists of waves that are oriented in all directions. Light waves that reflect off water (or any surface) are oriented horizontally – think of a flat sheet of paper, parallel to the water, coming toward you edgewise. That light is said to be polarized.

Now, the lenses of polarized sunglasses are specially treated so as to form filter that acts like a vertical picket fence (except that the spaces between the fence “slats” are extremely small). Imagine you’re holding a long rope that’s tied off against a tree. Between you and the tree is a picket fence, and the rope passes between two of the fence slats.

If you were to move your end of the rope rapidly up and down, you would create a wave in the rope, and that wave would pass right between the vertical fence slats and reach the tree. Now imagine moving the rope rapidly side-to-side. The narrow space between the slats would block the formation of a horizontal wave, which would never reach the tree.

That’s what polarized sunglass lenses do to reflected light. Light that would otherwise impede your ability to see into the water is filtered out before it hits your eyes. Light waves with a vertical orientation are allowed to pass through, revealing all those secrets from below the surface.

So, when on your lake exploring, wear your polarized glasses. You’ll get to know a little more about your lake. Not as much as if you looked below the surface through a snorkeling mask – but that’s a subject for another time.

Can walleyes make a lake clearer?

We all like our lakes to be clear, and most of us prize walleyes as a sport fish and table fare. But is there a connection between the two? Between walleyes and water clarity?

I learned at this year’s Wisconsin Lakes Partnership Convention that there can be. Scott Van Egeren, a water resources management specialist with the state Department of Natural Resources, gave a talk on the food chain in typical lakes such as we have in Wisconsin.

To oversimplify matters a bit for brevity, the food chain starts with one-celled algae (plant plankton, or phytoplankton), which are eaten by animal plankton (zooplankton), which include small crustaceans like Daphnia (water fleas). Fish such as cisco (planktivores) eat the algae eaters, and predatory fish, including walleyes, eat the cisco.

Now, what has that to do with water clarity? Well, in general, the lower the level of algae in a lake, the clearer the water. And in general, the more algae-eating water fleas are present, the less algae there will be. But what happens if cisco (and other smaller fish) are abundant and are gobbling up the water fleas? That means fewer algae-eaters, more algae, and cloudier water.

And here is where walleyes come in. Walleyes graze on cisco. If the walleyes are abundant, they can thin out the cisco and other smaller fish considerably. That means the water fleas and other algae-eaters have a chance to thrive, and the algae population goes down. And the water is clearer.

Now, of course, water clarity has to do with much more than just the walleye population. An important factor is the level of nutrients – which cause algae to thrive and can lead to nuisance blooms. Other factors include lake depth (deeper water has more capacity to absorb nutrients), surrounding land uses (which can contribute sediment in runoff), and wind and wave action, (which especially in shallow lakes can stir up sediments from the bottom).

But it’s interesting to think that a healthy population of walleyes can have a benefit beyond providing mornings and evenings of excellent fishing.

How do you like these odds?

Look in the shallow water around your pier these days and you may see schools of hundreds of tiny fish – probably newly hatched bass, perch, bluegills or other species. If you were to imagine many more such schools around the lake’s perimeter, you might assume your lake would soon be chock full of fish for catching.

The reality is far different. The odds of survival for these fry are exceedingly long. One scientific study used DNA tracking to estimate the success of spawning smallmouth bass on a lake in Ontario. To make a long story short, the study found that only 27.7 percent of male bass that acquired eggs (it’s the male who guards the young after the eggs hatch) had at least one offspring survive to the fall young-of-the-year stage. Just 5.4 percent of all the spawning males produced 54.7 percent of the total number of the fall young-of-the-year, which range in size from 1 1/4 to 3 inches.

To look at it another way, consider that female smallmouth bass deposit anywhere from 2,000 to 10,000 eggs on a spring spawning bed. Even under the best conditions, most eggs don’t survive. They’re vulnerable to changes water temperature and oxygen levels, flooding or sedimentation, disease and predation (as from panfish and crayfish).

When the eggs hatch, the larval fish live off a yolk sac attached to their bodies. Once the yolk is fully absorbed, the fry, about an inch long, rise from the bed and start eating on their own. For a time the male bass protects the school, but eventually he leaves and the fry scatter. They survive on tiny crustaceans until they are big enough to eat aquatic insects, then larger crustaceans and fry of other fish species that spawned later. As the fish grow, they face the same threats as the eggs – in addition to which all manner of predators feast on them.

When they’re small, they get attacked by bluegills, perch, pumpkinseeds and sunfish. As they grow, they become prey for walleyes, northern pike and muskies. Other enemies, again depending on the fishes’ size, include kingfishers, loons and herons, mink, frogs, and some snakes. The end result is that only a tiny fraction of the eggs laid in a spawning bed, and only a tiny fraction of the fry you may see near your pier, ever become adult bass. Yes, nature can be a cruel mother. I am certainly glad the odds of survival for our grandsons, Tucker and Perrin, are considerably better than for a newly hatched smallmouth bass.

The making of a magnet

Fisheries research today shows a powerful connection between “wood in the water" and a lake's fish populations. Trees fallen over from the bank and into the lake provide cover that protects fish fry from predators so they can grow up. How much wood is in your water?

Birch Lake, near Harshaw, where I live, is relatively barren of fallen timber, although I got to watch one specimen make the transformation from shade provider to fish haven, Just down the shore from our pier stood a tall white pine, its roots right at the waterline, its imposing trunk angled over the water at about 30 degrees from the vertical. We wondered if it ever would tip into the water -- it seemed to be defying the tug of gravity.

Well, two years ago, we got our answer. By early summer, the tree had tipped to about 45 degrees, and as I paddled by in a canoe one day I noticed a large, lengthwise crack at the base of the trunk. After a few weeks, the old pine came down, but not with a spectacular splash. It eased down, like a staccato second-hand on a watch, tick, tick, tick.  

During a couple of quiet evenings, sitting on the screen porch, I could hear the periodic cracking noises as the tree kept ticking down. Then one morning the tree lay in the water, extending out some 60 or 70 feet from shore. It was sad to see a venerable pine go down, but the plus side is that the tree now lies in what already was a fair walleye hole, just off the edge of a bed of emergent reeds, at a U-shaped dropoff that anglers like to call an inside turn. Snorkeling around the tree soon after it fell, I saw young-of-the-year smallmouth bass darting amid the twigs and still-green needles. The old pine was becoming a fish magnet. 

Of course, if we want more fish magnets on our lakes – more wood in the water – we have to do more than let nature take its course. The state Department of Natural Resources now promotes “fish sticks” – placing whole trees, or bundles of trees, in the shallows – as a fish habitat builder. Maybe if your lake isn’t rich in sunken timber along shore, it’s worth having your lake association consider a “fish sticks” project.

Diatoms: Where lake life begins

Weeds are springing up in your lake by now, or will soon – but the most significant plant growth that’s happening is not obvious to the eye.

As the water warms and sunlight continues to penetrate deep, diatoms are proliferating. These are one-celled algae that multiply profusely in colder water, which is high in silica and nutrients that built up over the winter.

“Diatoms use silica to build their cell walls,” according to an article in Minnesota Conservation Volunteer magazine. “They grow quite rapidly and often give the water a brownish hue. Because they cannot regulate their buoyancy in water, diatoms rely on currents or wind and wave action in lakes to keep them in the lighted zone, where sunlight penetrates shallow water. In the absence of wind, waves or currents, diatoms settle to the bottom of the lake and die.”

Later in the season, other kinds of algae take over. But a few more words about diatoms are timely and appropriate. For one thing, diatoms, seen under a microscope, are incredibly beautiful – the many species exist in a variety of symmetrical shapes.

More important, diatoms are an important part of a lake’s phytoplankton – the tiny plants that float in the water and form the base of the lake’s food chain or, to put it differently, the foundation for the lake’s food web. Diatoms and other phytoplankton perform the same basic function as grasses in prairies that support grazing animals.

Just like large rooted plants, diatoms live by photosynthesis. They make their food from sunlight, carbon dioxide and nutrients; they are called primary producers. Diatoms become food for plant-eating zooplankton – small animals like Daphnia (water fleas). These in turn are eaten by smaller fish, including game fish and panfish fry, which in turn become food for larger fish – bass, walleye, northern pike.

This of course is an over-simplified description of the food web, but it illustrates how important the diatoms and other phytoplankton are. Without them the food web would collapse – there would be no fish.

Another function of diatoms is that through photosynthesis they release oxygen. In fact, the diatoms, other phytoplankton, and larger aquatic plants make a net positive contribution to the dissolved oxygen on which fish and other lake creatures depend. 

So as you watch the water lilies, cabbage weeds, bulrushes, coontail and other plants pop up in your lake this summer, give a thought to the diatoms, out there by the billions, not doing much besides floating, yet helping to make the whole lake system function.

How we met: Dinner Lake

I just headed north on Highway 45 from Land O’Lakes, saw a plain wooden “Dinner Lake” sign at the first side road, took a right in the direction of the arrow, and followed the signs from there. The roads twisted back into the trees, first nice smooth asphalt, then much rougher asphalt, and then a skinny, bumpy gravel road for the last quarter-mile or so. The road dipped sharply down and bent around to the right, revealing the lake, a small blue jewel in a wooded hollow. Logs lay in the water on both sides of the boat ramp, and among them small bass hung motionless. I broke a piece off a twig and tossed it onto the water; a fish darted up, took it, and spat it out.

The boat ramp was on an almost circular bay, a narrow outlet giving way to the lake proper. I couldn’t see much of the lake itself, but several bare logs jutted out from the bay’s shore – great-looking cover. I hung around for a few minutes teasing the baby bass with bits of twig, then drove away, filing the spot in memory.

The next summer I bought a used blue fiberglass canoe. On a June weekend my friend Ed and I strapped it atop my 1964 Plymouth Valiant and drove north. We tented at the National Forest campground on Lac Vieux Desert and in the morning drove over to Dinner and slid the canoe in. We immediately found smallmouth bass among the logs, more than willing to smack a floating plug. As it turned out, loggy cover nearly surrounded the lake. We caught dozens of bass, about half of them above what was then the legal size of 12 inches.

I’ve returned almost every year since, with friends or alone. In time I discovered a rocky hump just off the east shore that is productive even when fish have deserted the shorelines. It’s a quiet lake, about 150 acres, ringed by small, well-kept cottages, most occupied just sporadically. I’ve never been able to spend an evening or weekend on the lake. In the early years there was a private campground on the east shore, but that soon closed. So it’s a lake I simply fish, once a year (with rare exceptions), almost as a matter of principle. After all, I discovered it. I don’t tell many people about it. My stock comment about it is: I’ll take you there, but I won’t just tell you where it is.

How about you? Where did your romance with your favorite lake begin? How did you two meet?