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



MIDGUT 



Figure 1. — Engvaulis mordax larva showing measurement site for midgut cell height. 



Evaluation of Midgut Criteria 



To evaluate the capacity of the midgut cell 

 height measurement to classify larval anchovy 

 condition, we graded 5-10 larvae taken daily 

 from 3 treatments (fed, feeding delayed 1 day, 

 and starved) using both O'Connell's (1976) histo- 

 logical criteria and the midgut cell height. We 

 assumed that the histological criteria (the sum of 

 the cellular grades for the brain, cartilage, 

 notochord, musculature, liver, and midgut) 

 would yield the best estimate of larval condition, 

 and we compared the power of each index to 

 predict past feeding history. 



RESULTS 



Diet-Induced Differences in Growth 



Growth of the fed control group was 0.41 

 mm/d, similar to published reports for northern 

 anchovy raised in the laboratory (Kramer and 

 Zweifel 1970; Hunter 1976b; Theilacker 1987). 

 Larvae experiencing a feeding delay of 1, 2, and 

 3 days were smaller at 10.8 days than larvae not 

 experiencing a delay, and as the starvation inter- 

 val increased, their final size decreased (Table 

 2). For the test of significance of size at age, P 

 was <0.01 for all delay combinations except the 

 starved 3 d/fed (S3/F) vs. the 4 d delay in feeding 



Table 2. — Diet-induced differences in growth of northern anchovy at a common age and at 

 a common feeding period (ris for common feeding period slightly less than n's for common 

 age). 



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