Results from the 2009-2010 Fall Walleye Index Netting (FWIN) Surveys in Washington State


Published: August 2012

Pages: 32

Author(s): Michael R. Schmuck


Effective management of recreational fisheries requires standardized sampling as well as the ability to manipulate fish populations through management efforts.   In addition, managers must have an understanding of how changes in biological systems affect angler participation and success.

Fall Walleye Index Netting (FWIN) methodologies were developed in Ontario and adopted by Washington Department of Fish and Wildlife (WDFW) fisheries managers in 2002 as a means of monitoring a wide variety of biological parameters in walleye populations in a standardized fashion.  Fisheries biologists from WDFW conduct FWIN surveys on five important walleye fisheries in eastern Washington (Figure 1) when water temps are 50-59°F, a range at which walleye are more equally distributed throughout lakes.  Sampling effort (i.e. nets set per lake) is based on lake size, or the minimum number of nets needed to collect 300 walleye (Table 1).

The FWIN nets are 8-panel gill nets 200 feet long and have a catch bias toward percids (walleye and perch).  Length and weight data, as well as relative abundance estimates, on other fish species are collected and presented but should be scrutinized.  For instance, low numbers of largemouth bass and bluegill are not a cause for concern since these species are more effectively sampled using a boat electrofisher.  In addition, length averages of smallmouth bass collected in gill nets tend to be higher than those collected via boat electrofishing and must be interpreted accordingly.

We collect length and age data on all walleye which allow us to determine the size distribution of the walleye population, the percentage of harvestable fish in the population and at what age walleye recruit to the fishery.  Walleye ages are determined from otoliths, which provide a precise age estimate. It is important to note that female walleye typically grow faster and larger than male walleye; however, females typically mature at an older age than males. When setting harvest regulations it is important for managers to keep this in mind to avoid overharvest of females which often grow to legal size at a younger age yet may not be reproductively mature.  This information becomes critical in systems with high harvest rates.  Fortunately walleye harvest in Washington lakes is at acceptable levels.  Length-at-age data, when combined with abundance data, also help us determine if a change in regulations is necessary or if regulations are helping us meet our management goals (Table 2).

The average number of walleye collected per net gives fisheries managers an accurate index of walleye population size.  Throughout this report we report this as catch per unit effort (CPUE ± 80% confidence intervals). Abundance estimates, when examined over multiple years, reveal trends in populations and allow managers to make informed decisions on possible changes in angling regulations.  Significant declines in abundance may signal a need for more restrictive regulations; whereas; increases in abundance, or stable populations at high abundance, may indicate the need for more liberal regulations (Figure 2).

Overall, walleye abundance in our FWIN waters is excellent with most lakes containing good numbers of harvestable fish.  The average CPUE for all lakes in 2009 and 2010 was 15 and 16 walleye per net, respectively.  In 2009 and 2010 approximately 51 percent of the walleye collected from all lakes were over 14 inches.  Growth of walleye in Moses Lake, Potholes Reservoir, and Scooteney Reservoir was excellent with walleye reaching 16 inches by fall of their second year.  Growth of walleye in Banks Lake and FDR was slightly slower with walleye reaching 16 inches by fall of their third and fourth year, respectively.

In speaking to many anglers and fishing clubs we have found that there is a strong catch-and-release mentality among many angler groups. Our data on walleye populations over the past nine years indicate that our populations can endure more harvest.  In fact, in 2006 we raised the daily limit to 8 walleye per day on Lake Roosevelt, Potholes Reservoir, and Moses Lake.  Unfortunately, few anglers took advantage of this as the results from our two year creel survey on Potholes Reservoir and Moses Lake indicated that very few anglers ever retained a limit of walleye.  We would like to take this opportunity to encourage anglers to harvest more walleye.

Besides walleye, yellow perch, smallmouth bass and lake whitefish were abundant in several of our FWIN lakes.  Yellow perch populations are quite cyclical; however, perch fishing on Banks Lake and Moses Lake can be excellent at times.  Smallmouth bass are abundant, and anglers report excellent fishing for them on all our FWIN lakes with the exception of Scooteney Reservoir.  Lake whitefish were abundant on FDR, Banks Lake, and Potholes Reservoir, yet are underutilized by most angler groups.  There is a small, but dedicated, group of wintertime lake whitefish anglers on Banks Lake who target whitefish under the ice.  We are trying to encourage anglers to diversify their angling experiences by fishing for, and harvesting, more lake whitefish.