CRiSP Harvest Model Frequently Asked Questions

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1. What does CRiSP stand for?
Columbia River Salmon Passage. The CRiSP project at the University of Washington School of Aquatic & Fishery Sciences started in 1988 with funding from the Bonneville Power Administration. The project's first computer model (called CRiSP 1) simulates the downstream passage of salmon smolts in the Columbia River. The CRiSP Harvest model has been under development since 1993.
2. Is CRiSP Harvest the same model currently being used by the Pacific Salmon Commission?
No. CRiSP Harvest is the same as the model used in 1995. The PSC Chinook Technical Committee adopted a new version of PSC Chinook Model in the fall of 1997. We plan to update CRiSP Harvest to this new version during 1998.
CRiSP Harvest was never updated to include the 1997 version of the PSC Chinook Model. See the Coast Model (currently the Coast Model does not have a graphic user interface).
3. Why don't model catches in catch ceiling fisheries equal the catch ceilings entered in the Catch Ceiling Window?
The answer is a little complicated. Basically, the reason is that the model does not include every stock that exists in the real world. Thus, the real world catches are always a little larger than model catches. The model catches have the correct relative values with the observed catches. The assumption, then, is that the stocks not in the model contribute the same relative amount to the fishery catches from year to year.
4. Why is the Inter-Dam-Loss rate really a survival rate?
Good question!! I guess the biologists were thinking about the salmon losses between the dams, but the mathematicians and programmers were thinking about survival between the dams. When doing the computations, it is easier to multiply the abundance by the survival rate to get the new abundance than it is to multiply the abundance by one minus the mortality rate.
5. How do I simulate changes in watershed habitat that affect salmon production?
Use the EV Scalar parameters. These represent brood year survival rates (i.e., survival from egg to age one). If you think a watershed activity will increase downstream survival for some stocks, you can increase that stock's EV Scalars to simulate this.
6. What is the difference between "Terminal Run" and "True Terminal Run"?
"Terminal Run" refers to the fish that leave the ocean and migrate toward the natal stream. Some of these fish are harvested by nearshore fisheries during the return migration, before they reach their natal stream. The "True Terminal Run" is the fish that actually enter the mouth of the natal stream and are subject to harvest in fresh water.
7. What is the difference between "Exploitation Rate" and "Harvest Rate"?
Exploitation rates are expressed in terms of the total coastwide abundance of a stock/age cohort, not the regional abundance. Thus, an exploitation rate of 0.10 for a given stock, age, and fishery means that 10% of the coastwide abundance of the stock/age cohort is harvested in the given fishery. Harvest rates refer to fishing mortality rates in terminal areas where the regional abundance (i.e., true terminal run) of the stock/age cohort is known.
8. What is a cohort?
A cohort is a group of fish that have the same demographic characteristics, such as belonging to the same age class of a given stock.