TILLMAN and STADELMAN: SIMULATION MODEL OF ANCHOVY FISHERY 



value of modelling this system is discussed, tak- 

 ing into account some of the present model's limi- 

 tations and shortcomings. 



DEVELOPMENT OF 

 THE SIMULATION MODEL 



General Description 



The basic model of the northern anchovy 

 fishery is formulated in terms of GAMES, the 

 general-purpose simulator of resource use sys- 

 tems developed by Gales (1972). This Fortran IV 

 program has been designed to simulate the ac- 

 tivities of major sectors involved in the harvest- 

 ing and marketing of renewable resources. The 

 sectors modelled by GAMES include locations, 

 stocks, harvesters, processors, regulators, prod- 

 ucts, and markets. 



A specific system such as the anchovy fishery 

 (Figure 1) is modelled by indicating, through ap- 

 propriate inputs, the number of entities in each 



Market - 

 Products 



Processors 



Regulators 



Los Angeles 

 Processors 



Harvesters 



Col. Fish 

 and Game 



Small 



Vessel 



Fleet 



Stocks 



Lorge 



Vessel 



Fleet 



Northern 

 Anchovy 



Location 



Southern 

 California 



Figure l. — Graphic representation of logical relations be- 

 tween sectors of the present northern anchovy fishery. From 

 Tillman ( 1972). 



sector and their logical linkages. The user must 

 also provide the values of parameters which 

 define system processes and structures and the 

 initial values of variables which describe systems 

 behavior. Tillman (1972) provides a detailed list- 

 ing of the values required for the northern an- 

 chovy model. Through appropriate control values, 

 the user also specifies that certain built-in deci- 

 sion routines be used or else provides algorithms 

 of his own design by adding subroutines to 

 GAMES or by modifying existing ones. The user 

 must also provide an appropriate biological model 

 of the stocks being exploited by the harvester- 

 processor sectors. 



The main GAMES program resembles the par- 

 tial listing given in Figure 2. The "Labelled 

 COMMON Blocks" reserves sections of memory 

 for storage of the values of parameters and vari- 

 ables used in common by the 11 subroutines. Sub- 

 routine TAPEIN is called first and reads in the 

 initial values of these parameters and variables, 

 including the starting and ending years of simu- 



PROGRAM MAIN 

 [Labelled COMMON Blocks] 

 CALL TAPEIN 



DO 110 YEAR=NYEAR1, NYEAR2 

 DO 10 MONTH = 1,12 



