4.5 - Catch Ceiling Management

The primary management tool of the Pacific Salmon Commission is the use of catch ceilings. A catch ceiling consists of an upper limit on the numerical catch for a fishery, or group of fisheries, for a specified time period. For example, the 1991 catch ceiling (upper limit) for the combined Southeast Alaska troll, net, and sport fisheries was 273,000 chinook. Note the following:

• catch ceilings are not established for individual stocks
• catch ceilings may include fisheries that are considered preterminal for some stocks but terminal for other stocks.

For each ceilinged fishery, ceilings are specified for each year of the simulation. During each simulation year, if the sum of the computed individual stock catches using input harvest rates (as modified by any fishery policy factors) does not exceed the ceiling amount, the ceiling has no effect (i.e., the stock abundance is such that the ceiling will not be reached given the specified stock exploitation rates). The model also allows ceilings to be "forced," or modeled as a fixed catch. A forced ceiling is called a "quota" and is taken every year regardless of the stock abundance. Most catch ceilings are modeled as quotas.

CRiSP Harvest uses a slightly different algorithm from the PSC model, but the net effect is the same. The CRiSP Harvest algorithm is described here, with significant differences from the PSC version noted.