Chapter 14. The Tucannon Salmon -- 4 Exercises

1 Add Similar, Precocious Fish

Draw a new version of the flow diagram in Figure 14.2 to include the possibility that some salmon return to the Columbia after only one year in the ocean. These are precocious fish, so name these fish "precos" in the model. Introduce a new converter called "Fraction Precos" as an input variable. You may assume that, except for their early return, the precocious fish have the same biological properties as the regular fish.

2. Add Dissimilar, Precocious Fish

Draw a new version of the flow diagram to add the precocious fish to the model. But in this case, you are told that the precocious fish are different from the fish described in Chpt. 14. You may assume that the precocious fish have a higher adult migration loss factor and they are not able to spawn.

3. Third Year in the Ocean

Draw a new version of the flow diagram in Figure 14.2 if you are told that the salmon spend three years in the ocean rather than two. The total life cycle is now five years rather than four. Suppose all other population parameters were the same as the previous model, and suppose the loss fraction during the 3rd in the ocean is negligible. Would the new model reach a dynamic equilibrium? If so, would the equilibrium value of the number of returning adults be higher or lower than the previous model?

4. Simulate the Third Year

Build the model diagrammed in the previous exercise. Use the model to check your answer to the previous exercise. Does the model confirm your reasoning? If not, do you need to change the model or change your reasoning?