2016 walleye 'young of year' numbers low, but big 2015 will help maintain population

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By Ted Pennekamp


Traditionally, as the weather warms up, more and more anglers take to their area waters to test their skills and try their luck. Each year is a bit different, but Mississippi River anglers in Pools 9 and 10 should expect a healthy fishery in 2017 despite relatively low numbers of certain species netted by DNR electrofishing crews this past fall.

One of the main species sought after by sport anglers on Pools 9 and 10 is the walleye. Over a two-day period in October of 2016, DNR electrofishing crews collected 295 walleye at night in near-shore areas and around wing dams below Lock and Dam 8. The adult walleye were between 10 and 27.3 inches.

The Young of Year (YOY) survey results in Pool 10 showed poor reproduction during the spring of 2016. There was a catch rate of only 22 YOY walleye per hour, which is the second lowest year for walleye reproduction since 2002. The lowest year since 2002 was 19 per hour in 2010.

The good news is that the exceptional walleye reproduction in 2015 of 166 YOY walleye per hour should help maintain the walleye fishery for the next several years.

“The walleye population seems to be declining slowly,” said DNR Fishery Biologist Patrick Short, who is based in Prairie du Chien. Short is part of a two-man electrofishing crew and he said various DNR crews electrofish each October from Lansing to Dubuque. 

Short said the theory is that high water, or flooding during the spawning time for walleyes leads to good reproduction because the larval stage walleyes drift out of the main channel and into the backwaters. He noted that the exceptional YOY in 2015 was most probably due to the high water in the spring that occurred during the walleye spawning time when the water temperature was about 46 degrees.

“The backwaters are more productive for walleye,” said Short. 2016 had several different periods of sustained high water, but the high water did not occur during the walleye spawning time. Thus, the fall survey in 2016 had low numbers.

Conversely, Short pointed out, there was flooding in the spring of 2001 during the walleye spawn. In October of 2001, the YOY class had very high numbers with more than 400 YOY caught per hour by electrofishing. A YOY class with numbers that high should help sustain the walleye population for the next decade, said Short, despite lower than average YOY classes in some of the following years.

Short said it doesn’t bode well for YOY numbers in October of 2017 because the high water of about 16 feet occurred this spring before the walleye spawn began.

Short said that walleye grow relatively fast within the first several months and reach an average of nine inches by October. Growth slows after that, and by their second year, the walleye are about 11 to 13 inches long. In their third year, the walleye become what is known as “recruited into the fishery” because they are, on average, 15 inches long and are harvestable by anglers.

Short said sauger spawn a little later than walleye and grow to an average of 8.5 inches by the fall.

Electrofishing is done at night and with the use of several lights. Short said curious anglers and boaters should stay away for safety reasons. The crews wear protective rubber suits, boots and gloves and have several safety precautions.

The Mississippi River is open to fishing year ‘round. The daily bag limit for walleye is six fish with a minimum length limit of 15 inches. There are numerous boat and shore fishing access locations. Pools 9 and 10 are part of the Upper Mississippi River Fish and Wildlife Refuge, which is in the states of Minnesota, Wisconsin, Iowa and Illinois. It was established in 1924. The refuge encompasses one of the largest blocks of floodplain habitat in the lower 48 states and is just over 240,000 acres extending 261 river miles from the Chippewa River in Wisconsin to near Rock Island, Illinois.

Short noted that other popular sport fishing species spawn at different times and water temperatures as those of the walleye. Northern pike spawn when the water temperature is about 34-36 degrees. Smallmouth bass spawn at between 60-65 degrees, and largemouth bass spawn at 63-67 degrees. Panfish such as bluegills spawn at about 70 degrees.

Electrofishing crews surveyed the backwater lakes in Pool 9 near Ferryville, Wis. and Lansing, Iowa in October and November of 2016 to determine the health of the fishery. According to the Wisconsin DNR, the unusually high water during the sampling efforts may have reduced the catch rates for largemouth bass, with a catch-per unit at 25 fish per hour. The bass ranged from 4.1 to 17.3 inches long.

The average size for largemouth was 10 inches. Thirty-five percent were larger than the minimum length limit for harvesting of 14 inches. The DNR says that bass in the 3 to 5-pound range are not uncommon in Pools 9 and 10. There is a five fish daily bag limit for bass.

 Electrofishing surveys for panfish conducted in October and November of 2016 in Pool 9 showed good populations of bluegill 5 to 10 inches and yellow perch 7 to 15 inches.

According to the DNR, efforts to rehabilitate backwater lakes in Pool 9 have greatly improved the fishery, thus making these areas an excellent place to fish year ‘round. The daily bag limit for bluegill, yellow perch and crappie is 25 with no minimum length limit.

It is always worth the effort to get out and see, learn and fish the Mighty Mississippi River with its mix of habitats, varying water depths and flows, islands, wing dams, mud flats, sand bars, backwater lakes, sloughs and side channels.

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