SM Link

Lake Francis Case Walleye/Sauger/Hybrids

Lake Francis Case Walleye (includes sauger and saugeye) Regulations (For specifics, see pages 16-18 in the 2015 Fishing Handbook)

Overall walleye abundance measured by the 2014 survey decreased to the lowest level observed and was similar to that measured in 2013.  High angler harvest coupled with low 2013 walleye production contributed to the reduction experienced the past two years.  Abundance of harvestable size walleye (those >15 inches), in the 2015 LFC population is lower than what was present in the reservoir prior to 2013.  Strong 2010 and 2011 walleye year classes should support a bulk of the sport harvest in 2015.  Walleye less than 15 inches are present in the population but are not as plentiful as in past years. These young fish are important, as they replace those fish harvested by anglers or lost to natural causes.

High walleye production during 2005 and 2006 currently provides some larger fish in the population. Moderate production in 2009 and excellent production in 2010 and 2011 should support the bulk of the harvest in 2015. Good walleye production occurred in 2012 while 2014, providing smaller walleye in the population.

Run-off into the Missouri River system is key for fish production. Localized run-off provides the reservoir with nutrients needed to produce plankton; small creatures that our bait-fish and newly hatched game fish eat. During periods of high run-off, the reservoir is capable of supporting high numbers of fish. Drought conditions seriously decrease the reservoir’s ability to produce and maintain fish populations. During low run-off periods, the reservoir simply does not have the nutrients needed to support large numbers of fish. As the graph below shows, run-off in the Missouri River basin has been at or above average (25.2 million acre-feet (MAF), depicted by the red line) from 2008-2011 following eight years of below normal conditions, which has increased reservoir productivity. Run-off into the Missouri River basin above Sioux City during 2012 was 19.7 MAF, a drastic decline from the 60 MAF measured during 2011, the highest on record.  2014 run-off was 35.0 MAF and the forecast for 2015 is 25.5 MAF.

For anglers unfamiliar with Lake Francis Case walleye, fish can be found year-round throughout the reservoir. However, the typical yearly pattern has a majority of the spawning size walleye moving into the upper 1/3 of the reservoir in late fall/early spring. After spawning in mid/late April, walleye begin to disperse throughout the reservoir. As water temperatures rise, walleye fishing can be good throughout the entire reservoir. Lake Francis Case typically sees most of its fishing use during the May-July time period. Consequently, this is also the time period when a majority of the walleye harvest occurs. When you have more people on the lake fishing, more fish are harvested, as shown in the chart below.

The primary forage fish species in Lake Francis Case is gizzard shad. Due to gizzard shad being intolerant of cold water temperatures for extended time periods, a majority of the young gizzard shad in Lake Francis Case die each winter. Fortunately, there are enough warm water refuges, associated with numerous artesian wells located throughout the reservoir, to over-winter a sufficient number of adult shad to produce a year class of shad each spring. Other forage fish species such as emerald and spottail shiners, young yellow perch, young white bass and a host of different minnows, shiners and darters provide a valuable source of prey.

Biologists often use catch rates to help determine the quality of a fishery. A catch rate is the number of fish caught per hour of fishing. For example, a walleye catch rate of 0.5 walleye/hour means it takes an average of 2 hours for an angler to catch a walleye. Catch rates of walleye and other sport fish that depend on young gizzard shad for food are typically highest in May and June as food resources are limited due to the die-off of young gizzard shad during winter. Gizzard shad begin spawning in late May or early June.  Newly hatched gizzard shad reach a size desirable to walleye by about mid July, at which time catch rates of walleye typically decline on Lake Francis Case due to food being plentiful. The chart below helps illustrate how angler success on Lake Francis Case is influenced by prey-fish abundance.

Biologists index fish condition or plumpness using relative weight (Wr). LFC walleye relative weights are typically in the high 70s or low 80s. As the chart below illustrates, LFC walleye relative weights of smaller fish are typically above 80 while relative weights of larger walleye typically fluctuate between 70 and 80.