Screen 1

Experiment with the harvest fraction to maximise the total harvest over a 40 year time period. The population is quite small at the start, but it has the potential to grow rapidly under pristine conditions.

YOUR CHALLENGE:

Your job is to find a strategy for setting the harvest fraction as conditions change over time.

Each fraction applies for a two year interval. Select the harvest fraction and click the "run for 24 months" button to simulate the next two years. You are free to consider a different harvest fraction for each harvesting period.

YOUR CLASSMATES' CONTRIBUTION:

Meanwhile, your classmates are free to vary the four parameters on the control panel at any time during the 40 year time period. Their job is to test your ability to react to conditions beyond your control.

CAN YOU HANDLE RANDOMNESS?

To test your harvest strategy under more realistic conditions, click the switch to "turn on" some random variations. The green light will signal that there will be random changes in the smolt migration loss fraction. The migration loss fraction will vary around the "value in a regular year" by +or- 5%. If the regular value is 90%, for example, the randomly varying value could be anywhere from 85% to 95% with equal probability.

WARNING GAUGE

The warning gauge shows the size of the population of two year old salmon in the ocean. These are the fish that will soon enter the Columbia. The gauge incluces color warnings:

red: less than 6 thousand

yellow: from 6 to 12 thousand

green: over 12 thousand

You may assume that this warning system was implemented by your staff in case you wish to react to the warnings. But you, not your staff, is responsible for achieving the maximum cumulative harvest. You are under no obligation to react to the warnings.

River Development Parameters: (controlled by classmates)

The two migration loss fractions depend on the extent of hydro electric Development on the Snake and Columbia Rivers. The default parameters apply to "predevelopment condtitions." The smolt loss would increase to 95% and the adult loss would increase to around 38% if we wish to simulate the impact of the six dams between the Tucannon and the ocean.

Watershed Development Parameters: (controlled by classmates)

The egg loss fraction and the carrying capacity of the Tucannon depend on the extent and type of land use in the Tucannon watershed. Egg loss is 50% under pristine conditions. With the land use of the 1970s, egg loss is probably around 75%. The pristince carrying capacity is 400 thousand. With the degraded conditions of the lower river in the 1970s, the carrying capacity would be around 170 thousand.