BIOSTATISTICAL ANALYSIS 29 



basic input data can be varied over any range of values that may 

 be of interest. For example, fish prices, gear expenses, depreciation 

 rates, operating costs, etc., can be entered as constants and may be 

 changed from run to run. All of the biological factors, such as the 

 entry patterns of the fish, their migration routes and rates of move- 

 ment can also be varied from run to run as can the gear availability 

 and absolute and relative gear efficiency. 



The present program allows the computer to start with any desired 

 set of descriptive information about the salmon runs and the fishery 

 for one season. From this information the computer will compute 

 daily catches, the escapement to various spawning grounds, the total 

 cost of harvesting the run, and the catch and cost per individual unit 

 of gear for each type of gear. Some idea of the scope of the output 

 of the computer program may be obtained by looking at the dictionary 

 in the Appendix of definitions for the code names of the variables. 



One of the most important features of the computer program 

 used for the simulation model is the management decision making 

 processes which are built into the program. The rate of exploitation 

 of the salmon runs in international, Canadian, and United States 

 waters is regulated by the International Pacific Salmon Fisheries Com- 

 mission. The regulations are designed to provide an adequate escape- 

 ment of sockeye and pink salmon to each of the major spawning 

 systems and also to divide the total catch equally between the United 

 States and Canadian fisheries. As might be imagined, this complex 

 regulatory objective necessitates a highly flexible regulatory scheme. 

 On the basis of the past performance of the Salmon Commission and 

 from talks with personnel of the Commission, a scheme was devised 

 and built into the computer program. In fact, three basic regulatory 

 schemes are available with the present program. The one that was 

 used for the majority of the runs reported upon here was designed to 

 close the fishery any time that the actual fishing mortality exceeded 

 a given specified level. The particular level used in the program was 

 20 per cent escapement for a normal-sized run. If the run size dropped 

 to half, the desired escapement was raised to 30 per cent. On the 

 other hand, if the run size increased to four times the normal level, 

 the desired escapement was reduced to 15 per cent. If at any time 

 during the season the fishing mortality exceeded the desired level, botii 

 the American and Canadian fisheries were closed. From June 20 

 through August 29 (see Fig. 9), this regulation was formulated on 



