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Results of the 2005 Fall Walleye Index Netting (FWIN) Surveys PDF Format - [159K]
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Results of the
2005 Fall Walleye Index Netting (FWIN) Surveys Abstract
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.
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