NOTE Canino and Caldarone: Fluorometric techniques for determining nucleic acid contents of fish larvae 161 



0.0 



100 o 



150 



RNA (/ig mL homogenate) - FIA 



DNA (/tg mL 



12 5 15.0 17.5 

 homogenate) - FIA 



25 



2 



40 



60 

 RNA/DNA -FIA 



Figure 1 



Mean RNA and DNA concentrations and RNA/DNA ratios of 24 crude fish 

 homogenates obtained by flow injection analysis (FIA) versus conventional 

 fluorometric analysis (CFA). Solid line represents a 1:1 correspondence be- 

 tween the two methods. Dashed line is the geometric mean regression be- 

 tween the two estimates. Species abbreviations as in Table 1. 



sensitivity, precision, and sample throughput. Mean 

 coefficients of variation (V x ) for DNA concentration 

 estimated by FIA and CFA in this study (3 to 4%) 

 are similar to those reported for replicate assays of a 

 pooled fish homogenate using FIA (Caldarone and 

 Buckley, 1991), another two-dye procedure (Clem- 

 mesen, 1988), and a single-dye method (Clemmesen, 

 1993). In this study, the mean V x values for RNA con- 

 centration were 3 to 5% higher when determined by 

 FIA and CFA for multiple homogenates than for FIA 

 estimates of a single, pooled homogenate (Caldarone 



and Buckley, 1991) but are comparable to those re- 

 ported by Clemmesen (1993) for RNA estimates of 

 pooled fish homogenate using a single-dye technique. 

 The RNA and DNA concentrations of fish 

 homogenates were consistently lower when estimated 

 by CFA compared with FIA. Calibration between the 

 two methods by functional regression relationships 

 established a reasonable basis for comparison of results 

 (Fig. 2), although considerable differences in mean es- 

 timated nucleic acid concentrations and RNA/DNA 

 were still evident. We emphasize that sample homo- 



