Jacobson et al.: A biomass-based assessment model for Engraulis mordax 



723 



Conclusion 



Finding the appropriate compromise between real- 

 istic (but potentially overparameterized and impre- 

 cise) models and parsimonious (but simplistic and 

 potentially biased) models is an important part of a 

 stock assessment research (Ludwig and Walters, 

 1985, 1989; Hilborn and Walters, 1992). The best 

 choice among models depends on the task, data avail- 

 ability, and complexity of the situation. Our work 

 indicates that models intermediate in complexity 

 between simple surplus production and complex age- 

 structured models can perform well under a wide 

 range of circumstances for estimating the biomass 

 of stocks such as northern anchovy. 



Acknowledgments 



W. Garcia (Centro Regional Investigacion de Pes- 

 quera), Pesquera Zapata S.A. de C.V., and LMR Fish- 

 eries Research provided Mexican fishery data. E. 

 Konno and P. Wolf (California Department of Fish 

 and Game) provided U.S. fishery data. A. MacCall, 

 B. Lenarz (Southwest Fisheries Science Center, 

 Tiburon Laboratory), R. Methot (Alaska Fisheries 

 Science Center), R. Parrish (Southwest Fisheries 

 Science Center, Pacific Fisheries Environmental 

 Group), P. Smith, and J. Hunter (Southwest Fisher- 

 ies Science Center), and an anonymous reviewer 

 made suggestions that improved the scientific basis 

 and presentation of results. 



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