To catch a walleye, know one. Just ask Paul Radomski

No matter an angler's skills, catching walleyes on the opener can be easy or challenging, depending in large part on the weather — not only the weather on opening day, but on days leading up to the season's first walleye outing.

Yet weather aside, anglers who expand their walleye knowledge and improve their fishing skills can more regularly put fish on a stringer or in a live well. Perhaps 10% of anglers catch between 50% and 70% of boated walleyes.

To include yourself in the fortunate 10%, understand that as DNR fisheries biologist Paul Radomski says in his forthcoming book, "Walleye, A Beautiful Fish of the Dark'' (University of Minnesota Press) that persistence and a willingness to fail are crucial to successful angling. Understand also that most walleye trips end without any walleyes caught.

Yet the odds can be tipped in an angler's favor, especially from opening day through mid-June — perhaps the most productive fishing period in Minnesota — if an angler's increased understanding of walleyes and their habits is combined with 1) time-tested gear and bait deployed on, 2) lakes or rivers with reasonably abundant walleye populations.

So, using Radomski's book as a guide, along with other information, let's get smarter about walleyes and walleye fishing:

• Depending on spring weather, Minnesota's best naturally reproducing walleye lakes can be opening-day hotspots. These include Cass, Kabetogama, Lake of the Woods, Leech, Winnibigoshish, Upper Red, Mille Lacs, Pepin, Rainy and Vermilion. These 10 lakes account for about 40% of Minnesota anglers' annual walleye harvest.

• This spring, unfortunately, hasn't been much of a spring. As a result, on the opener, ice likely will be a problem for anglers on Rainy Lake and Lake of the Woods and perhaps on Vermilion — with Leech, Winnie, Cass and Upper Red on the bubble. Looking for alternative walleye waters for the opener? Check out lesser-known prospects, including DNR survey results for individual lakes, online here.

• Keep in mind: Whether fishing in spring, summer, fall or winter, water temperature, light penetration and oxygen levels are key determinants in locating walleyes.

• Water temperature will be a concern for walleye anglers on Saturday's opener, particularly for lakes in the north. Lakes and rivers that are too cold, with ice only gone by a day or two, often don't trigger walleye appetites.

• The best walleye fishing often occurs beneath cloudy skies when a ripple — commonly known as a walleye chop — roils a lake surface. Sunny days with lakes that are mirror flat often make fishing tougher.

• Yet in walleye fishing as in all fishing, exceptions to "rules'' are common. Walleyes, for example, often feed without regard to conditions. Best as a result to keep a line in the water as often as possible, changing baits, locations and water depths — or all three — as often as necessary.

• Keep in mind also that walleyes, like other fish, often hang out on weed edges and along other changes in "structure.'' But no one bottom type is productive at all times. Sometimes walleyes can be found on rock piles, other times along drop-offs and still other times, as on Mille Lacs, on mud flats.

• Some walleyes could still be spawning on some northern Minnesota lakes when fishing begins at 12:01 a.m. Saturday. Spawning can begin under lake ice, Radomski notes. But peak walleye spawning occurs when water reaches 42 to 50 degrees.

• Male walleyes appear at spawning sites before females and hang out there long after the egg-depositing females have departed for deeper water. This is why most opening-day anglers who fish shallows used for spawning primarily catch male walleyes, which are smaller than females.

• Unseen as opening-day anglers patrol these shallows, some eggs deposited by female walleyes have gone unfertilized by males, while others are fertilized but die, perhaps, as Radomski says in his book, after being washed ashore in a storm or perhaps due to persistently cold water.

• Fertilized eggs that incubate successfully produce embryos that hatch in about 21 days.

• Survival rates from fertilization to hatching range from 1% to 60%. This results either in bountiful "year classes'' of walleyes in Mille Lacs and other key Minnesota walleye producing lakes, or, if survival conditions are sketchy, small year classes.

• By early summer, newly hatched walleyes, or "fry'' have reached "fingerling'' stage, with scales and fully developed fins. Fingerling walleyes are bigger and faster than similarly aged yellow perch, a primary food source for young walleyes. Among predators wanting to chomp on young walleyes in addition to older yellow perch are northern pike, burbot, sauger, smallmouth and largemouth bass, and larger walleyes.

• By the end of a walleye's third summer, the youngster is about 12 inches long. By the end of its fourth summer, 15 inches. From age 3 to 4 , Radomski says, a walleye is most vulnerable to anglers. By about age 5, Minnesota walleyes will sexually mature and their growth will slow. In the southern U.S., walleyes can mature at 2 years old, and in northern Quebec as late as 15 years.

• The biggest male walleye in a population might be only three-fourths as large as the biggest female.

• If such a claim could be validated, it's likely most walleyes caught on the opener will be fooled by jig-and-minnow combinations. But not all jigs are the same: They come in different colors, shapes and sizes. Minnows differ, too. Fatheads are cheapest and generally a good bet. Shiners can be (but aren't always) more productive for walleyes. And red tail chubs often are best (but are costly and can be difficult to find).

• To avoid detection by bigger fish and to help them prey on smaller fish, when seen from above a walleye's dark dorsal fin blends with a dark lake or river bottom, while from below, a walleye's white or yellowed white underbelly blends against a lake's light-diffused surface.

• In Mille Lacs, biologists found that walleyes primarily eat yellow perch year-round. Larger walleyes eat other walleyes, particularly in fall, and cisco when available.

• How popular is walleye fishing? About 1% of the U.S. population fishes for walleyes specifically, Radomski says, and about 12% of American anglers target walleyes primarily. In Canada, walleyes represent about 26% of the national sportfish catch.

• Catch-and-release walleye fishing — like that imposed in most instances on Mille Lacs anglers — can sometimes conserve a population. But because walleyes tend to live near lake bottoms, practicing catch and release can under some circumstances have little or no benefit to a fishery. Fishing methods (no deep hooking, as can often happen with sliding-sinker rigs), water temperature (can't be too warm) and depth at which walleyes are hooked must be "right'' for catch and release to benefit a resource.

• Regarding walleye stocking and how much is too much, a lake's walleye population can't be continually enlarged by adding fry or fingerlings. A lake has only so much biological carrying capacity, which must be shared by all life within it.

• A walleye's peak light sensitivity is for wavelengths in the green portion of the spectrum, which is the same portion of the spectrum that penetrates deepest into lakes. This makes sense, Radomski notes, given that walleyes spend most of their time seeking prey near lake and river bottoms.

• Like cats, dogs and horses — but unlike humans — walleyes have specialized eyes that allow them to hunt in low light. Their primary prey, yellow perch, lack this advantage, as do a major walleye predator, northern pike.

• Walleyes, however, likely have blurry close-up vision, leaving them at times unable to distinguish between a yellow perch, for example, and an angler's lure or bait.

• Sauger, which, like walleyes and yellow perch, are members of the perch family (Percidae), can see and hunt in even darker or more turbid waters than walleyes.

• Are walleyes territorial? Not always. In small lakes, walleyes travel only fairly short distances. But in large, low productivity lakes, they might travel 100 miles in a month, either alone or in schools.

. . .

Walleye anglers who spend increasing amounts of time on the water often change how they define "successful" fishing.

A morning, afternoon or evening spent on a lake or river is in many ways its own reward and reinvigorating — regardless of the number of fish caught.

Also, as with all time spent in nature, a renewed appreciation of the value — and fragility — of land and water often results, and with it an understanding of the need to conserve.

"For walleye and the rest of nature, the will to survive is stronger than the desire to give up,'' Radomski concludes in, "Walleye. A Beautiful Fish of the Dark," adding:

"I take solace that life moves forward and that tomorrow could be better. Near the shore, I see walleye fry struggling to rise up from the cobble-strewn lake bottom — free of the detritus. In communion with walleye, we too leave our past in the detritus. We are all betting that tomorrow will be better."

. . .

Editor's note: Advance orders for, "Walleye, A Beautiful Fish of the Dark" (324 pages. $24.95, University of Minnesota Press) can be made through bookstores or from the publisher's website, upress.umn.edu.