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6. Spatial Fisheries Model
model runs. Otherwise, the model pauses after each change, and only resumes its run if you choose Resume from the pull-down menu or via a button defined for that purpose.
Flight simulators can be very effective tools to quickly explore model response to alternative assumptions, and to communicate your model and
findings to others . Through this communication, another dynamic component may be added to the modeling process : the model may have initiated
debate among users, and may have prompted important revisions of the
model, that would not have been made, had the model not been readily accessible to them .
6.5. Questions and Tasks
1. a) How does a change in the efficiency of fishing technology affect the
results of Sections 6.2 and 6.4? Assume a small, incremental increase
in the parameter V throughout the timeframe over which you run the
model.
b) Assume that changes in V do not occur autonomously, but are themselves a function of the profits made by the fishermen . For example,
some of the profit is used to change effort, some is used to upgrade
fishing technology. How do your findings from part a) change?
2. a) In the model of Section 6.3 we implicitly assumed that each region is
of the same size. Set up that model so you can vary the size of the reserve ranging from 10% of total area to 90% of total area without
changing the number of elements in the array. Is there some general
relation between reserve size and maximum fish population or between reserve size and maximum catch?
b) Make the necessary modifications to the user interface of Section 6.4
so that users can choose the size of the reserve .
3. In Sections 6.1-6 .3 changes in effort in each period are proportional to
the profits that occur in that period. Explore alternative rules to change
effort; for example:
a) Assume that there is a lag-time (of one or more periods) in the response of effort to changes in profit. (For this purpose, you may want
to use STELLA's DELAY built-in function .)
b) Assume fishermen form expectations about the next period's catch,
and base their changes in effort on those expectations.
4. How will the results of Section 6.3 change if the displaced effort from the
reserve is not allocated to the other regions?
5. Disaggregate the populations in each of the four regions in Section 6.2
into three age cohorts, following the example of Chapter 4. Assume different rates of reproduction and movement for each of the three cohorts .
Explore the population dynamics of your model under a range of assumptions about these rates. Are there some general statements that you
6. Spatial Fisheries Model
model runs. Otherwise, the model pauses after each change, and only resumes its run if you choose Resume from the pull-down menu or via a button defined for that purpose.
Flight simulators can be very effective tools to quickly explore model response to alternative assumptions, and to communicate your model and
findings to others . Through this communication, another dynamic component may be added to the modeling process : the model may have initiated
debate among users, and may have prompted important revisions of the
model, that would not have been made, had the model not been readily accessible to them .
6.5. Questions and Tasks
1. a) How does a change in the efficiency of fishing technology affect the
results of Sections 6.2 and 6.4? Assume a small, incremental increase
in the parameter V throughout the timeframe over which you run the
model.
b) Assume that changes in V do not occur autonomously, but are themselves a function of the profits made by the fishermen . For example,
some of the profit is used to change effort, some is used to upgrade
fishing technology. How do your findings from part a) change?
2. a) In the model of Section 6.3 we implicitly assumed that each region is
of the same size. Set up that model so you can vary the size of the reserve ranging from 10% of total area to 90% of total area without
changing the number of elements in the array. Is there some general
relation between reserve size and maximum fish population or between reserve size and maximum catch?
b) Make the necessary modifications to the user interface of Section 6.4
so that users can choose the size of the reserve .
3. In Sections 6.1-6 .3 changes in effort in each period are proportional to
the profits that occur in that period. Explore alternative rules to change
effort; for example:
a) Assume that there is a lag-time (of one or more periods) in the response of effort to changes in profit. (For this purpose, you may want
to use STELLA's DELAY built-in function .)
b) Assume fishermen form expectations about the next period's catch,
and base their changes in effort on those expectations.
4. How will the results of Section 6.3 change if the displaced effort from the
reserve is not allocated to the other regions?
5. Disaggregate the populations in each of the four regions in Section 6.2
into three age cohorts, following the example of Chapter 4. Assume different rates of reproduction and movement for each of the three cohorts .
Explore the population dynamics of your model under a range of assumptions about these rates. Are there some general statements that you