| dc.description.abstract | Walleye (Stizostedion vitreum) spearing and angling harvest
levels are set annually for lakes located in the ceded territory
of northern Wisconsin, based on adult population estimates. For
most lakes, population estimates are obtained from linear
regression models that describe the relationship between past
population estimates and lake size. Lakes are classified
according to the recruitment source (i.e. stocked or natural) of
the population, and regression models differ accordingly. This
thesis evaluates the current recruitment classification system,
identifies features of lakes that predict both the presence of
walleye and the presence of self-sustaining walleye populations,
and improves precision and accuracy of current regression models.
The relationship between lake size and walleye abundance
was quantified for two life stages, age-0 and adult, in 172
northern Wisconsin lakes. Age-0 and adult walleye abundance was
higher in lakes sustained by natural reproduction than in lakes
sustained by stocking. This suggests that patterns in walleye
abundance differ between lakes with self-sustained and stocked
populations in northern Wisconsin lakes and that these patterns
may be established during the first year of life, at least
partially due to recruitment source.
Limnological features of lakes described walleye presence
and absence in 2037 lakes, and presence of self-sustaining and
stocked walleye populations in 392 lakes in northern Wisconsin.
Lake area, maximum depth, and water source were the best
predictors of walleye presence in lakes. The presence of self-sustaining
populations of walleye was best predicted using pH and
watershed area. I conclude that physical, chemical, and
biological features of lakes may be used to discriminate lakes
where walleye presently exist from lakes that presently do not
contain walleye, and lakes with self-sustaining from stocked
walleye populations.
The relationship between lake size and adult walleye
abundance, estimated by spring mark-recapture surveys, was
quantified for 166 lakes in northern Wisconsin, 1990-1997. Four
models described differences in adult walleye abundance as a
function of lake size for lakes with self-sustaining versus
stocked populations and for drainage versus landlocked lakes.
Models were improved by adding environmental variables, to
further explain variation among lakes. I conclude that accuracy
of estimates of adult walleye abundance derived from regression
models based on recruitment source may be improved by
incorporating limnological variables. | en_US |
