Here’s to Hoover-Mouth

There are species of fish in your lake that you may rarely if ever see, yet are important to the health of the fishery. The white sucker is a classic example.

You may know this fish best as bait. Raised in ponds, it is sold in increasing sizes for walleyes, northern pike and muskies. If like me you grew up on a Lake Michigan tributary, you may have fished for suckers using a dip net hung by a rope from a bridge, in springtime when the fish migrate upriver from the lake to spawn.

If your lake contains suckers, why don’t you see them? Well, because they tend not to take what anglers offer. I’ve fished for more than 50 years and have caught just one white sucker from a lake on hook and line.

Suckers are mainly bottom-feeders and have mouths well adapted to that purpose. The leathery lips aim downward instead of straight ahead, so the fish can cruise along, dining in comfort, casually vacuuming up food like insect larvae, worms, small mollusks and crustaceans, plant matter and fish eggs from the sediment. In turn, suckers are a vital food for favored game fish; they may also be eaten by herons, loons, bald eagles and osprey.

White suckers live in almost any lake and stream here in Northern Wisconsin. In fact, they’re abundant throughout the Northeast and Midwest U.S. and in parts of the Northwest. They do fine in clear, clean waters but also tolerate relatively low dissolved oxygen and so can thrive in turbid urban waterways.

Suckers have fine scales. Sides are dark greenish with a metallic luster; the belly white, and hence the common name. Adults can grow up to 20 inches long and weigh two pounds or more; musky anglers are known to use those at the top of the size range for bait in the fall.

Spawning generally starts when the fish are about four years old (later in colder climates where they grow more slowly). Spawning season runs from April to early May. The fish move into streams or, in lakes, select bottoms of gravel or coarse sand. The actual spawning happens at night. Most often, two males mate with one female. With one male to each side, the female lays 20,000 to 50,000 eggs, which the males fertilize.

The fish do not make spawning nests and do not care for the eggs, which simply sink to the bottom. The eggs hatch in five to ten days, and a week or two later the fry leave the spawning area and disperse.

Thus are born swarms of fish on which your lake’s most prized species may depend for growth. So even if you never see suckers on your lake except in your bait bucket, be sure to assign them a little respect. Here’s to Hoover-Mouth!

How does your lake get its water?

You’ve read here about classifying lakes by trophic state – how poor or rich in nutrients they are. But that’s not the only way to categorize them. Another, just as interesting, is by how water gets in and out.

The number of lake types based on source of water depends partly on who is doing the defining. The Wisconsin Department of Natural Resources lists four types, but there is a fifth that many geologists mention. Here are five basic lake types found in Northern Wisconsin and Upper Michigan:

Drainage lakes. On these lakes, a stream brings water in, and a stream takes water out. That is, the lake has an inlet and an outlet. Some lakes may have more than one of each. The water level in these lakes tends to stay fairly constant. Think of a bowl into which you run a slow flow of water from the tap: An equal amount of water flows in and flows out. I live on a drainage lake and its level is largely self-regulating. In 30 years, through wet times and dry, there has been at most a foot of difference between the highest and lowest levels.

Spring lakes. These lakes have no inlet on the surface, but they do have an outlet. They get their water mainly from groundwater flowing in. Many streams originate in spring lakes, which are quite common in northern Wisconsin.

Seepage lakes. These lakes have no stream flowing in or out. Their water comes mainly from rainfall and runoff, sometimes supplemented by groundwater. Their water levels are therefore cyclical, rising and falling with wet and dry years and their effects on the water table.

Drained lakes. These lakes are like spring lakes in that they have an outlet but no surface inlet. They differ in that they are not fed by groundwater – they get their water almost solely from rainfall, snow and runoff. For that reason, their levels can fluctuate greatly. During long dry spells, the streams flowing out of these lakes may dry up. Drained lakes are uncommon here in northern Wisconsin.

Perched lakes. These lakes are truly landlocked. They have no inlet, no outlet, and no contribution from groundwater. In fact they sit on relatively high ground, above the water table, with dense bottom sediments that hold the water in. Water levels in perched lakes can drop dramatically during long dry spells.

If you want, you can add a sixth type of lake: Reservoirs. These of course are like drainage lakes in that they have a stream inlet and outlet. The difference is that they were created by humans – they wouldn’t exist if not for dams. Here in the northern Wisconsin we have the Willow, Rainbow, Turtle-Flambeau, Chippewa and other smaller flowages.  

Which type is your favorite lake? If you don’t already know, consider doing some investigating to find out.

Minnows? Are You Sure?

Soon after ice-out I do canoe reconnaissance: slow paddle around the shoreline to look for signs of life. When I did that recently here on Birch Lake (at Harshaw), I encountered huge schools of little fish at the far-in end of what we call Indian Bay.

My mind reflexively said, “Minnows!” But of course that was both non-specific and taxonomically incorrect. The vertical black stripes on these guys, anywhere from about 1.5 to 2.5 inches long, clearly labeled them as young yellow perch.

It amazes me how soon fish fry take on the markings of adults. Baby smallmouth bass, for example, have the signature black-tipped tails and red eyes. Largemouth bass have the black stripe along the side, northern pike the oblong oval spots. And so it goes.

The young fish seem to mimic adults in temperament, too. Little muskies, for example, are hyper-aggressive. Last summer, I caught a 4-inch musky that slashed at and grabbed a crappie minnow impaled on my hook.

But back to the matter of minnows: We tend to apply that label to any small fish, especially in schools. That’s probably because we refer to the baitfish we buy at the tackle shop as minnows (again not precise, but a well-accepted term).

Scientifically speaking, the term “minnow” applies to a family of fish defined not by size but by characteristics. Members of the minnow family have one brief dorsal fin with nine or fewer soft rays. They have smooth-feeling scales that may come off when the fish is handled. They do not have true spines in their fins. They have no teeth in the jaw but have rows of toothlike structures on the bony frame that supports the gill tissues. Their teeth are in the throat and help grind food.

Most minnows are in fact small, a few inches long. That’s true of the shiners we use for bait – they are in fact minnows. But the minnow family also includes carp that can grow to three or four feet or longer and can weigh 50 pounds or more.

Chances are the schools of fish you see beside your pier will not be minnows but small game fish or panfish. If you can net a few (not easy, I admit), you’ll get a clue to what’s breeding in your lake. The fish I saw in Indian Bay on my canoe ride assuredly were not minnows; from their numbers I can conclude that our lake’s perch of brought off some successful hatches.

That of course is not the same as successfully reproducing: Hatched fry do not a large or stable population make. Those little perch have a tough gauntlet to run before they reach adult size. All I can do is wish them well.

Waiting for Water

Just before hamburgers were served to son Todd and me at Birch Lake Bar a week ago, co-owner Ed stopped by our table and lamented the lake’s condition.

I’d been enjoying the extended thaw – greatly, I might add – but to Ed the lake’s surface of deep slush meant the end of snowmobile season, the end of ice fishing, and so a tough time for business. I can certainly sympathize: an early thaw means different things to different people.

Now the question of the day is: When will our lakes open up? That depends on how the weather behaves from here on, though the past two weeks of well-above-average temperatures have given the thaw a nice head start.

Last year and the year before, the ice went out here on Birch Lake a few days after the official fishing opener (first Saturday in May). It went out a great deal earlier in 2010, the first year we had our land here – I remember wading in the lake, quite comfortably, in mid-April.

2011 was a different story. On April 16, when our family held a ceremonial groundbreaking for the cabin that has since become our year-round home, the lake was still frozen solid, the day cold, wind-blown snow stinging our faces. We drank our champagne huddled inside the RV trailer that served as our first shelter.

As for 2012, I have written evidence of an early ice-out. An entry elsewhere on this blog says I put the pier in on April 7, the Saturday before Easter. Are we due for another early open-water season? Signs point that way, but we can’t forget what April and May were like last year: Cold, cold, and more cold, with a couple of April blizzards tossed in.

Right now, as I write, on Sunday, March 15, it’s pleasantly mild, about 50 degrees, and the forecast, if it can be trusted, calls for highs well into the 40s for the next several days. The snow has melted off the metal components of our pier, arranged neatly on shore, and off the cedar pier board sections I stacked and covered with a tarp last November.

If you’re like me, you’re aching for the ice to be gone and for the start of whichever open-water recreation you prefer. It’s a wondrous time – the days getting longer, the clock sprung ahead, loons on their way north, the long months of spring, summer and fall awaiting, full of promise. We could do worse than to have an early ice-out bring that promise forth sooner.

Magic on ice

Assuming our cold snap goes away and stays gone, something almost magical will soon happen to your lake’s ice. It’s called candling, and it reveals a property of ice that’s hidden from us most of the time. It’s fascinating, but it also leads to a significant hazard for those venturing out for late-season ice fishing or other adventures.

As the thaw sets in, lake ice changes from what we know as a strong, monolithic structure to a matrix of crystals, arranged (if imagined from above) as hexagons, like the cells in a bee’s honeycomb, though by no means as perfect. These crystals align vertically, from the top of the ice to the bottom; they are shaped somewhat like candles.

In its candled state, ice is often called “rotten.” You can see how weak it is in this video. A man (wearing a life vest, over shallow water) walks on candled ice and repeatedly breaks through, even though the ice is 13.5 inches thick and if intact would support a 9,000-pound vehicle with a 3:1 margin of safety.

How and why does this happen? The best explanation I got came from Dan Heim, an old friend, an Arizona resident, and author of the Sky Lights blog about astronomy, meteorology, and earth science.

As ice forms, he tells me, the mostly hexagonal crystals grow from the surface down. In the dead of winter, the crystals are strongly fused (frozen) together so that the ice appears monolithic.

“Ice expands as it warms, up to the point where it melts,” says Dan. “As the thaw approaches, the ice goes through many cooling and warming cycles, and that’s where the stress to form cracks begins to build. When you look at images of candled ice, you see that most but not all candles are hexagonal. Because of impurities in the water, the fractures are sometimes non-hexagonal. As things warm up, the ice preferentially cracks along the crystal boundaries.

“Once the cracks form, that’s where additional melting happens, further separating the candles. The load-bearing capacity of the ice, which is proportional to the square of its thickness, starts dropping as soon as the microscopic cracks form.” And dropping quite fast, one might add. So for safety’s sake, stay off of candled ice.

Another thing about candled ice: It can be almost musical. If you were to find a thick sheet of such ice driven by wind up onto shore, and if you were to tap at it, candled crystals would tumble off, making a soothing sound a bit like a set of wind chimes. Magical indeed!

A place for lake lovers

What are you doing April 23-25? If you love your lake, you might want to consider attending the 2015 Wisconsin Lakes Partnership Convention, or at least a part of it.

I’ll attend this year for the fifth time, and I wish I had started long ago. It’s an inspiring event. You spend a couple of days surrounded by scientists, communicators, lake association leaders, advocacy group representatives and others all interested in one thing: making lakes better.

For a few days you shed your political affiliation, forget what you do for a living and just learn, in hands-on workshops, field trips, lecture sessions, poster presentations, an exhibit hall, and casual break-time and lunchtime conversations.

Sessions cover all manner of subjects: aquatic invasive species, wetland protection, fishery surveys, nutrients and algae, shoreland zoning and other government policies and, perhaps most important, how to get involved in improving the lakes you care most about.

My all-time favorite session, during my first trip to the convention, was a half-day workshop on aquatic plants. There were slide presentations followed by hands-on exercises examining specimens of common and less common plants and using what’s called a taxonomic key to identify them by name. I’m a fisherman by avocation, but now when I’m out on the water, I am much more attuned to the greenery below and on the surface – it’s no longer just “weeds.”

Also of note are the plenary (whole-group) sessions, which generally feature inspiring speakers. This year, the keynote speaker is Marion Stoddart, a citizen leader and grassroots organizer who is largely responsible for the conversion of New England’s Nashua River, once among the nation’s most polluted rivers, into a candidate for the National Wild and Scenic Rivers System.

I can’t wait to hear her talk. I know I haven’t done as much as I could for lakes, including my own, and her words may help nudge me into more action.

The convention will be at the Holiday Inn Convention Center in Stevens Point. That’s not so far away, and the registration fees are affordable. There’s a good chance that one or more leaders of your lake group plans to attend. If you’re interested in doing more for your lake, you might want to consider going along.

I know I appreciate lakes more deeply, and feel better qualified too advocate for them, because I’ve gone to this event. 

Eutrophic lakes: It’s a process

Mention a “eutrophic lake” and many people will picture a stagnant pool, matted with algae, murky, bad smelling, and generally unpleasant to be around.

It really isn’t that simple. A eutrophic lake by definition is at a fairly advanced stage of a process called eutrophication, whereby the lake accumulates high levels of plant nutrients, chiefly nitrogen and phosphorus. But the mere fact of being eutrophic does not mean a lake is “dirty” or “polluted” or otherwise undesirable – although that can be and often is the case.

Nitrogen and phosphorus are necessary for plant growth. Your lake, whether eutrophic, oligotrophic (few nutrients) or mesotrophic (in between), contains these nutrients. Otherwise there would be no lily pads, no fish-attracting cabbage weeds, and no tiny algae that form the base of the food chain.

The problem comes when the amounts of nitrogen and phosphorus become excessive. Blame for that often gets placed on human sources – uncontrolled stormwater runoff from city yards and streets, runoff from over-fertilized farmland, poorly maintained septic systems, and others.

But nutrients also come from natural sources as, for example, when a shallow lake is surrounded by and receives runoff from land with fertile soils and abundant organic matter. That is to say, some lakes are naturally eutrophic, and no amount of water-quality regulation or watershed management will change that.

Of the two main nutrients, phosphorus is the one that – here in Northern Wisconsin and in most regions of inland lakes – controls the pace of eutrophication. Some of the nitrogen in lake water exists as nitrate – an atom of nitrogen and three atoms of oxygen (NO₃). Over time, biological processes convert this nitrate to nitrogen gas (N₂), which then escapes to the atmosphere. So there is to some extent a natural “brake” on the buildup of nitrogen in lakes.

It’s different with phosphorus – it accumulates in lakes, and when present in excess it can cause explosive growth of algae. Darby Nelson, in his brilliant book, “For Love of Lakes,” explains with great clarity how this works.

He first describes the ingredients in his wife’s blueberry muffins and how, if she happens to have only two teaspoons of baking powder, she can only make one batch – no matter how much flour and sugar and how many eggs she may have on hand. Then:

“In lakes, except in unique circumstances, the ‘tin’ of phosphorus usually empties first. Compared to demand, it is phosphorus that is available in least supply, the bottleneck to alchemy. Little phosphorus in lake water begets few cyanobacteria, algae and aquatic plants. Lots of phosphorus begets lots of blue-green algae, or aquatic plants, or both.”

So if we want to forestall eutrophication in our lakes, the best thing we can do is take measures to keep phosphorus out.