SOMERTON AND KOBAYASHl: FISH LARVAE CATCHES IN PLANKTON NETS 



design of the entry and retention experiments. 

 When these assumptions are violated, unbiased 

 estimates of entry and retention probabihties 

 can sometimes be obtained by restricting the 

 analysis to either large or small larvae to ensure 

 that avoidance and extrusion do not simulta- 

 neously influence the size distribution. If the size 

 range of interest must be as broad as possible, 

 however, then the methods described in this 

 paper can be used to correct for differential ex- 

 trusion and avoidance and unbiased length-fre- 

 quency distributions can thereby be obtained. 



ACKNOWLEDGMENTS 



We thank Kevin Landgi'af for helping with the 

 field sampling and Tina Xavier for measuring the 

 larvae. George Boehlert, Tom Clarke, Nancy 

 Lo, Bruce Mundy, Jeffrey Polovina, and two 

 anonymous referees reviewed the manuscript 

 and offered helpful suggestions. 



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