FISHERY BULLETIN: VOL. 84, NO. 2 



range of exploitable size, intensive fishing would 

 produce a substantial change in the population size 

 structure. A plot of the mean fork length by day of 

 fishing for the three species (Fig. 4) shows very lit- 

 tle change in fork length even for P. zonatus where 

 68% of the exploitable stock is estimated to have 

 been removed. Thus, the mean size of the fish in a 

 catch may be a much less sensitive indicator of 

 changes in the population size than catch rates, at 

 least over the short term. 



ACKNOWLEDGMENTS 



I wish to thank Alec D. MacCall and William E. 

 Schaaf whose reviews resulted in an improvement 

 in the formulation of the variable catch Leslie model. 

 This paper is a result of the Resource Assessment 

 Investigation of the Mariana Archipelago at the 

 Southwest Fisheries Center Honolulu Laboratory, 

 National Marine Fisheries Service, NOAA. 



41 



40 



39 



E 



o 38 



x 



K 

 O 



5 37 



O 36 



35 



h ! r 



Pristipomoides zonotus 



Pristipomoides ouricillo 



i i i i i 



_i_ 



23456789 10 

 DAY 



12 13 14 



Figure 4.— Mean fork length for each day of fishing for Pristi- 

 pomoides zonatus, P. auricilla, and Etelis carbunculus. 



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