The issue of stocking a lake can be volatile.
Anglers, local residents, and business owners may believe that a certain
lake should be stocked with lake trout. After all, it may improve fishing
in the lake, which can have a positive effect on the local economy.
Like many issues faced by natural resources personnel, the issue of
stocking is not that clear-cut. Before stocking a lake, natural resources
personnel must determine if lake trout can succeed in a given lake.
Like all animals, lake trout depend on specific environmental conditions
for their survival. In this lesson, you will decide whether the temperatures
and oxygen concentrations of Ice Lake can support lake trout.
Consider what you know about the needs of
lake trout. What water qualities are necessary for lake trout to survive
in a given lake? What factors need to be considered before stocking a
lake? What social and economic issues are related to stocking? What can
happen if a lake is "incorrectly" stocked?
Lake trout require specific environmental
conditions for their survival. They seek out water temperatures of
about 913° C during the summer. In the cool, relatively
unproductive lakes that lake trout commonly inhabit, oxygen concentrations
are near saturation.
If summer temperatures exceed approximately 20° C or
if oxygen concentrations fall below about 8 mg/l conditions are not
ideal for the survival of adult lake trout.
As a Minnesota Department of Natural Resources
fisheries biologist you need to determine whether or not to stock Ice
Lake with lake trout. Your decision will be based primarily on dissolved oxygen (DO)
and temperature - two very important water quality measures
for fish survival.
Think about how to efficiently approach
answering the question of whether or not to stock lake trout. You know
you have the temperature and DO data available from WOW. How many sampling
times and different days do you feel you will have to analyze? How will
you organize and analyze this data so you can make your decision?
Make sure you have an organized way to record
your DO and temperature data before you visit the "Data" area
of the WOW website.
Data Management and Analysis
You may want to construct a graph(s) of
temperature and oxygen concentrations in Ice Lake. If you do, be sure
to label axes and include titles and legends on your graphs.
Interpretation of Results
Explore the lake survey data of the Minnesota
Department of Natural Resources (http://www.dnr.state.mn.us/lakefind).
Consider the common physical characteristics of Clearwater, Greenwood,
Saganaga, and Seagull Lakes (all in Cook County). These lakes all support
healthy lake trout populations. Lake trout lakes are most common in
Northeastern Minnesota, but even there lake trout are near the southern
edge of their range.
According to your data, can lake trout
succeed in Ice Lake? How would you explain your reasoning to area anglers?
You need to make a presentation to the DNR
and concerned local citizens about the ability of lake trout to survive
in Ice Lake. The data and your analysis should provide most of the information
you need to complete the report. Your teacher will specify the format:
a written paper, an oral presentation, a poster, or multi-media presentation.
Be prepared to answer any questions about your research findings.