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					NAME ________________________________________


Scenario #1: cisco and smallmouth bass

Peaceful, placid Lake Kitchell is located near the southern limit of the range of cisco, Coregonus
artedii, a lake-dwelling planktivore (a fish that eats zooplankton). It is also near the northern
limit of the range of smallmouth bass, Micropterus dolomieui. Smallmouth bass in Lake Kitchell
eat age-1 cisco and nothing else, but this has not been a problem for the cisco population because
the population of smallmouth bass in Lake Kitchell has always been fairly small. Two models,
"cisco.run" and "smallmouth.run", describe the conditions for cisco and smallmouth bass growth
in Lake Kitchell from May 1st (day 1) to November 1st (day 180).

Look at the temperature input data. In an average year, the maximum summer water temperature
in Lake Kitchell is 16°C for about two months. Now, using the "User Input Parameters" tab,
change the model so that age-1 cisco grow from about 10 g to 100 g between May and
November, and so that smallmouth bass grow from about 250 g to 260 g in the same time period.

1. What is the total consumption (in grams) and P-value of a cisco during this time? of a
smallmouth bass?




2. On about what day or days are the specific consumption rates and growth rates (in
joules/gram/day) of the two fishes at their peaks? What are the peak values? (Use the graphing
function to answer this question.)




3. On what days is the specific growth rate of the cisco less than 60 j/g/d?



4. What is the gross conversion efficiency of these two fishes under these conditions? (Gross
conversion efficiency is simply the ratio of [total growth] : [total consumption].)




Ecologists studying Lake Kitchell project that its temperature will increase 4°C due to global
warming over the next 25 years, and they ask you, a bioenergetics expert, what will happen to
the cisco and smallmouth bass if this happens. Go into the "temperature" input data files for both
models and increase the temperatures by 4°C.
5. Maintain P at the same values as in the previous model runs. Under the higher temperatures,
what are the total consumptions (in grams) of the two fishes? What are their final weights?




6. Re-examine the specific growth rates and consumption rates of the two fishes. What are the
peak values of each parameter for each fish, and when do they occur?




7. On what days is the cisco growth rate less than 60 j/g/d?



8. What are the gross conversion efficiencies of the fishes now? (Remember to recalculate total
growth!)




9. Would you guess that the optimal temperature for consumption and growth of cisco in Lake
Kitchell is greater than or less than 18°C? How about smallmouth bass?




10. Write a brief paragraph synthesizing what will happen to cisco and smallmouth bass growth
and energetics in Lake Kitchell if global warming happens, compared to current conditions.
Explain what happened and why. Hypothesize what you think will happen to the cisco and
smallmouth bass populations, and justify your hypothesis with evidence from the bioenergetics
simulations. (Use the back of this page if you need more room.)
NAME ________________________________________


Scenario #2: larval bluegill survival

Peaceful, placid Lake Vander Zanden is a popular spot for sport anglers who want to catch
bluegill, Lepomis macrochirus. You work for the Department of Natural Resources (DNR), and
you are in charge of managing the bluegill sport fishery in Lake Vander Zanden. You have
found that one of the most important aspects of maintaining a healthy population of bluegill is
overwinter survival of young-of-the-year (YOY) bluegill. The model "bluegillYOY.run"
describes the conditions for YOY bluegill growth in Lake Vander Zanden from May 1st (day 1)
to November 1st (day 180).


1. Click the "diet proportions" tab and look at the YOY bluegill's diet. (The values are
proportions (they sum to 1); dipterans are larvae of flying insects such as midges.) Describe, in
words, how a larval bluegill's diet changes over the course of the summer. This needn't take
more than 2-3 short sentences.



2. Using the "User Input Parameters" tab, change the model so that bluegill grow from 0.25 g to
1.5 g between May and November. Past data show that overwinter survival of YOY bluegill in
Lake Vander Zanden is poor unless they reach a weight of 1.5 g by November 1st. What must
the P-value and total consumption (in grams) be for a bluegill to reach this size threshold?



3. Plot the cumulative consumption of detritus, zooplankton, and diptera by individual through
time. What are the approximate totals for each at the end of the simulation? (BE CAREFUL--
note the Y-axis labels!!!!)



4. Plot the specific growth rate (in joules per gram per day) of the bluegill through time. What
explains the slow growth at the beginning? Why do you think it changes on day 15?


Describe (or draw) the general shape of the plot.
What is the approximate peak growth rate, and approximately when does it occur?

5. Fix P at 0.8 for these questions:

What is the final weight (g) of the bluegill at normal temperatures? Will overwinter bluegill
survival be good or poor?



In an unusually cold summer (decrease all temperatures 4°C), what is the final weight? Will
overwinter bluegill survival be good or poor?



6. Again, plot the specific growth rate of the bluegill (in joules/gram/day). Describe the plot
(when it peaks, where, etc.); it should look different than the plot in #4.




On about day 120, you should see a big drop in growth rate. What else about the bluegill's
energetics is changing on day 120? (Hint: look at your User Input data)




One day, you read that climatologists are predicting a summer that is much cooler than normal.
You expect that Lake Vander Zanden will be 4°C below normal, as in the previous simulation.
As a manager, you must take steps to prevent high juvenile bluegill mortality.

7. Using the bioenergetics model, figure out a way to get YOY bluegill to grow to 1.5 g by
November 1st, despite the poor temperatures. Keep P fixed at 0.8. This will take a bit of
experimenting with the User Input data. (Think carefully about what you can control in nature
on a rather limited budget. Is it possible for some management decision to cause a switch in fish
diets?..can you influence temperature? Prey energy content? Prey proportions?) Write a brief
description of what management actions you would undertake to ensure YOY bluegill survival.
(Use the back of this page if you need more room).

				
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