FISHERY BULLETIN; VOL. 76, NO. 3 



Tomlinson system exhibits a convenient flexibil- 

 ity with a minimum number of coefficients, the 

 peculiar coupling of the coefficients to the non- 

 linearity of the system often provides more flexi- 

 bility than we care to have, and a conventional 

 least-squares statistic may not be sufficient to con- 

 trol the system in the estimation procedure. In 

 consequence, many constraints have to be imposed 

 on the system in order to obtain convergence in the 

 estimation procedure and to insure reliability in 

 the coefficient values thus estimated. 



ACKNOWLEDGMENTS 



We would like to thank R. I. Fletcher, J. J. Pella, 

 and C. G. Walters, each of whom reviewed the 

 manuscript and offered many helpful suggestions. 

 This research was supported by NORFISH, a 

 marine research project of the University of 

 W^ashington Sea Grant Office and the National 

 Marine Fisheries Service (Grant 04-7-158-44021, 

 Office of Sea Grant, National Oceanic and Atmos- 

 pheric Administration, U.S. Department of Com- 

 merce). Financial support was also provided by the 

 National Research Council of Canada and by the 

 Minister of Education of Quebec. Contribution 

 No. 492 of the College of Fisheries, University of 

 Washington. 



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