242 



Fishery Bulletin 91(2), 1993 



frequency distribution" (Barry & Tegner 1990). Fur- 

 thermore, classifying populations as "growth domi- 

 nated" or "mortality dominated," as these authors have 

 done, introduces terms that obscure rather than illu- 

 minate the analysis of size distributions, much in the 

 manner of r- and K-selection comparisons. 



Size data should be part of every demographic study 

 because they contain a record of the recent past his- 

 tory of a population. Such data ultimately can be used 

 to estimate parameters, such as Z in Eq. 5, that fre- 

 quently are difficult to obtain, or to test assumptions 

 concerning annual variability in recruitment or mor- 

 tality. There currently is no substitute for population 

 studies that include not only size data but also inde- 

 pendent estimates of growth and, where possible, 

 survivorship. 



Acknowledgments 



Support for this work was provided by the National 

 Science Foundation, landing tax funds from commer- 

 cial sea urchin fishermen administered through the 

 California Department of Fish and Game, and San 

 Diego State University in the form of a sabbatical leave 

 for the senior author. 



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