3.9 Lesson Name: Reducing ocean troll fisheries.

Ocean fisheries are generally the least selective fisheries. That is, they tend to harvest the greatest number of stocks. How much will reducing ocean troll fisheries improve escapements of weak stocks?

Analysis Approach:

We will drastically reduce the Alaska and West Coast of Vancouver Island troll fisheries and observe the effect on the Lyons Ferry stock and the Columbia River Net fishery.

How To Do It:

1. Launch and run the model.
2. Set the Default Stock to Lyons Ferry.
3. Click the Stocks Menu.
4. Click Stocks Graph.
5. Click Escapements.
6. Record the Lyons Ferry Escapement in year 1998.
7. Close the Escapement Graph.
8. Repeat steps 2 through 7 to record the Upriver Brights escapement in year 1998.
9. Set the Default Fishery to Alaska Troll.
10. Click the Fishery Menu.
11. Click Fishery Graphs/Catches/Total.
12. Record the Alaska Troll catch for year 1998.
13. Close the catch graphs.
14. Repeat steps 9 through 13 to record the catches for the WCVI Troll and Columbia River Net fisheries in 1998.
15. Click Fishery/Catch Ceilings.
16. Select the Alaska Troll fishery.
17. Click the tab that contains year 1998.
18. Set the 1998 Alaska Troll Catch Ceiling to 50,000 and click apply.
19. Repeat steps 16 through 18 to set the 1998 WCVI Catch Ceiling at 50,000.
20. Click run the model.
21. Repeat steps 2 through 14 to record the 1998 escapements for the Lyons Ferry stock and the 1998 catches in the Alaska Troll, WCVI Troll, and the Columbia River Net fisheries.

1. How much did the Lyons Ferry escapement go up in 1998?
2. What happened to the Columbia River Net fishery catch in 1998? Why?