Results of the 2005 Fall Walleye Index Netting (FWIN) Surveys

Walleye (Sander vitreus) have become one of the most popular sport fish in Washington and continue to grow steadily in popularity. Although they inhabit only twelve lakes in eastern Washington they also occupy the entire mainstem of the Columbia River from the Canadian border to near the mouth at the Pacific Ocean. In general, due to favorable conditions, Washington’s walleye populations grow faster and establish higher relative abundances than the average conditions in other areas of North America that walleye inhabit. Because of the walleye’s importance as a renewable recreational resource, the Washington Department of Fish and Wildlife (WDFW) began the FWIN surveys in 2001 in order to manage them more efficiently and effectively. Six waters were sampled in the fall of 2005 (figure 1).

All the data collected during the fall walleye surveys are obtained by using the standardized Ontario FWIN protocol. This standardized sampling method allows valid comparisons of results between waters and from year to year. It also gives us both a short term and long term perspective on each population. During the fall, walleye are more evenly distributed throughout the lake and the water column providing the most consistently good time to obtain a representative sample of the population. Sampling begins when surface water temperature lowers to 59°F and must stop when it reaches 50°F. The walleye are collected with gillnets only. The nets are 200 feet long by six feet deep. Each net contains eight panels of increasing mesh size from one inch to six inches (stretched mesh). Each net is set in a randomly selected site for approximately 24 hours. In order to make effort comparable, the number of net sets is determined by the surface area of the water being sampled. Each walleye captured is sampled for total length, round weight, visceral fat weight, and gonad weight. Sex and sexual maturity are determined by examination of the gonads. Otoliths are taken from each fish for age and growth analysis.

The results from our 2005 surveys are shown in this report in the form of graphs followed by a brief explanation of each. The relative abundance graph (the average number of walleye per net) compares values from all lakes for all years sampled, on a single graph. After that, there are three individual graphs for each lake: size distribution (the percentage of walleye in each size group), age distribution (the percentage of walleye in each age group), and species composition (the percentage of each different species in the fish community for each lake). Please bear in mind that since we sample exclusively with gill nets for the FWIN surveys, the species composition graphs may or may not accurately represent the fish communities from each lake. These graphs will only provide a general picture of the fish community make-up. Like any single capture technique, gill nets have particular biases for and against certain species and sizes of fish. They are however, the best single technique for capturing a representative sample of the walleye populations in the fall. A more detailed report comparing all FWIN sampling from 2001-2005 with a more in-depth analyses of the changing population’s characteristics will be completed and posted on the WDFW website later this year.