Advisor: Michael Bozek
Walleye (Sander vitreus) spawning habitat and recruitment in Northern Wisconsin Lakes
Walleye
(Sander vitreus) is a popular sport fish that generally spawn on gravel
and cobble substrates with low embeddedness, near shore, and in shallow
water (Raabe 2006). The addition of rock spawning habitat to increase
walleye recruitment has been a generally accepted and popular management
action. However, an assessment of 20 rock habitat projects in Northern
Wisconsin Lakes showed that none of the habitat projects succeeded in
significantly increasing recruitment (Neuswanger & Bozek 2004). The
objectives of this study are to develop a standardized method to
quantify walleye spawning habitat in lakes and to determine the
relationship, if any, between spawning habitat and recruitment (i.e.
determine how much spawning habitat is necessary for proper
recruitment). Fifteen study lakes with varying amounts of walleye
spawning habitat and known walleye populations were
chosen in Northeastern Wisconsin. Walleye spawning habitat in each lake
was measured using four different methods: 1) take habitat data at 250
random transects, 2) measure the linear area of shoreline gravel/cobble,
3) measure the length of spawning habitat, preliminarily defined as at
least 50% gravel and/or cobble substrate with an embeddedness of two or
lower, at 0-1, 1-2, and 2-3 meters from shore, and 4) measure the length
of spawning habitat at .29 meters deep. Each method will be evaluated in
terms of accuracy and feasibility and a regression model will be created
for spawning habitat and recruitment. It is hypothesized that successful
recruitment requires a minimal amount of spawning habitat, and that in
most cases poor recruitment is linked to other potential limiting
factors such as fish community structure, resource availability, and
year effects. A standardized method to quantify spawning habitat along
with an understanding of the relationship between habitat and
recruitment will aid in determining whether habitat is a limiting factor
in lakes exhibiting poor recruitment. 