FISHERY BULLETIN: VOL. 87. NO. 3, 1989 



Incidental information from delayed feeding 

 experiments (Table 1) revealed that, depending 

 on diet, age of 5 mm northern anchovy ranged 

 between 9 and 19 days. This 10 d range in age 

 at size (due to feeding history) has important 

 implications for size-at-age mortality estimates. 



In conclusion, our study indicates that the ab- 

 solute midgut cell height of northern anchovy 

 larvae is a practical criterion to use for estimat- 

 ing rates of starvation. The cell height measure- 

 ment yields reliable estimates of feeding history, 

 is resistant to autolysis, and is rehable in form- 

 alin-fixed specimens. Thus, the special ichthyo- 

 plankton tows and preservatives required for a 

 histopathological index are not needed when the 

 midgut index is used. The midgut index is as 

 sensitive to nutritional conditions as the histo- 

 logical index and does not require the rigorous 

 calibration needed for the morphometric tech- 

 nique (Theilacker 1986; Setzler-Hamilton et al. 

 1987). Also the midgut character is much easier 

 and faster to measure than scoring the histo- 

 logical features of northern anchovy tissues, and 

 it does not require a solid background in histo- 

 logy for the person scoring. Because of these 

 features, the midgut index is practical for 

 routine estimates of starvation rates of larvae in 

 the sea. In addition, unlike previous methods, 

 the duration of tow is not a constraint because 

 the character does not degrade with time and a 

 sample representative of the water column can 

 be taken. 



ACKNOWLEDGMENTS 



Many thanks to Nancy C. H. Lo for assisting 

 with the statistical treatment of the data and to 

 Jack Metoyer, for measuring many of the 

 anchovy larvae. John Hunter read the manu- 

 script and made valuable suggestions, as did an 

 anonymous reviewer. 



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