3.7 Lesson Name: Shut down the fisheries!

How quickly will weak stocks recover if all harvesting is stopped?

Analysis Approach:

Use the meta-slider function to set all Harvest Rate Scalars (for each stock, fishery, year combination) to near zero (setting these scalars to zero might cause a program crash because it may create a "divide by zero" error). This will effectively eliminate all harvests.

How To Do It:

1. Launch and run the model.
2. Click the Harvest Menu.
3. Click Harvest Rate Scalars.
4. Click the tab including year 2000.
5. Click the "Y Box", the "F Box", and the "S Box" at the top of the slider window.
6. For the year 2000, type in a Harvest Rate Scalar of 0.05 (do not use the sliders; they don't work properly). You may have to wait up to a minute for all the parameters to be changed.
7. Click apply and OK.
8. Click the Run button on the tool bar.
9. When the run is complete, set the Default Stock to Lyons Ferry (or another stock that had a declining escapement trend under the default management strategy).
10. Click the Stocks Menu.
11. Click Stock Graphs.
12. Click Escapements and observe the escapement trend.
13. Resize and move the Escapement Graph so the map icons are visible.
14. Click the Wand button at the upper left portion of the graph window.
15. Move the mouse pointer over other stock icons to observe escapement trends for other stocks.

1. How many stocks reach an equilibrium condition (i.e., a constant escapement trend) by year 2017?
2. Are there any stocks that do not increase when all fishing is eliminated?
3. How many years of a "no fishing" strategy would be needed to bring all stocks up to an acceptable escapement level?
4. How much lost revenue would the fishing fleets suffer under a "no fishing" strategy?