DEVELOPMENT AND EXAMPLE APPLICATION OF A SIMULATION 

 MODEL OF THE NORTHERN ANCHOVY FISHERY 



Michael F. Tillman^ and Donald Stadelman^ 



ABSTRACT 



A computer simulation model of the reduction fishery for northern anchovy, Engraulis mordax, is 

 described. The biological subroutine of this model is an age- structured paradigm which is modified to 

 account for age-dependent exploitation and variable recruitment. To demonstrate the model's utility, 

 two example applications are presented which provide insight into the problems of evaluating alterna- 

 tive regulations while lacking perfect knowledge of economic or biological behavior. The model's 

 current value lies in its use as a tool to identify research needs. 



Based upon the systems analyses of Tillman 

 (1972) and Stadelman (1974), it appears that the 

 northern anchovy, Engraulis mordax Girard, con- 

 stitutes one of the largest latent fishery resources 

 available to American flag vessels. Relative to its 

 estimated biomass, only a minute fraction of this 

 species is harvested when compared, for example, 

 to catches taken by the fishery for Peruvian an- 

 choveta, E. ringens. The present northern an- 

 chovy fleet consists of only a small number of rel- 

 atively old vessels, and the processing capacity of 

 the fish meal plants servicing this fleet is quite 

 inadequate. Thus, unlike many major fisheries of 

 the United States which are marked by overex- 

 pansion and overcapitalization, the northern an- 

 chovy fishery is still underdeveloped. 



According to the above authors, this lack of 

 development can be attributed to a variety of 

 natural and artificial barriers. The natural bar- 

 riers comprise those constraints over which man 

 has little or no control, including lack of predic- 

 tive ability concerning the short-term behavior of 

 the market for fish meal. Moreover, there pres- 

 ently is lacking definitive biological knowledge 

 concerning the inherent variation in size and 

 availability of the northern anchovy population, 

 its dynamic stock-recruit feedback mechanisms, 

 and its natural mortality processes. These gaps 

 provide the context of a dynamic and variable en- 

 vironment within which this fishery system oper- 

 ates and with which its managers must contend. 



The artificial barriers, on the other hand, are 



^Northwest Fisheries Center, National Marine Fisheries Ser- 

 vice, NOAA, 2725 Montlake Boulevard East, Seattle, WA 98112. 



^Institute of Governmental Research, University of Washing- 

 ton, 3935 University Way N.E., Seattle, WA 98195. 



institutional constraints which man has imposed 

 upon the system. While the intent of these rules 

 or regulations may be to govern the activities of 

 fishery participants, their overall effect, in the 

 opinion of Tillman (1972) and Stadelman (1974), 

 has been to thwart economic development of the 

 fishery. For example, small quotas for reduction 

 purposes are intended to prevent overcapitaliza- 

 tion of the fishery but have also acted to hinder 

 the much needed replacement and renovation of 

 antiquated reduction equipment. Other artificial 

 barriers and their apparent effects, as perceived 

 by the foregoing authors, include the following: 

 areal and temporal closures to protect stocks, but 

 which act instead to reduce harvest efficiency; 

 union rules to maintain employment levels, but 

 which in fact work to prevent use of technological 

 innovations that would reduce harvesting costs or 

 increase efficiency; landing taxes of $2 per ton to 

 pay for research and management, but which in 

 fact act to reduce substantially the returns ob- 

 tained by private interests. 



If an appropriate goal for decision makers is to 

 foster economic development of the northern an- 

 chovy fishery, then the above institutional bar- 

 riers would seem to present opportunities for 

 achieving that goal. Consequently, a computer 

 simulation model has been developed which pro- 

 vides the means for evaluating the biological and 

 economic consequences of changing various regu- 

 lations governing this fishery. The purpose of this 

 study is to briefly describe this simulation model 

 and to present two examples of its application 

 which demonstrate some of its utility. These ap- 

 plications focus on the evaluation of alternative 

 regulations when given imperfect knowledge of 

 biological or economic behavior. Finally, the 



Manuscript accepted May 1975. 



FISHERY BULLETIN: VOL. 74, NO. 1, 1976. 



118 



