minimum at initiation of feeding on day 7 indi- 

 cates that protein is probably an important energy 

 source during this period although this includes a 

 22'7f decrease in protein upon hatching, the major- 

 ity of which may be lost with the chorion. Two 

 periods of decrease in RNA content were observed. 

 One occurred just prior to hatching; the other just 

 prior to feeding initiation. No significant net de- 

 crease in the DNA content of eggs or fed larvae 

 was observed between any sampling periods. 



The decrease in protein and RNA content (Fig- 

 ure 1) as well as the decrease in the RNA-DNA 

 ratio (Figure 2) prior to feeding initiation resem- 

 bles the pattern observed for starved larvae. Even 

 in the presence of excess food the RNA-DNA ratio 

 fell from 4.9 at the end of the yolk-sac stage to 3.0 

 at initiation of feeding on day 7. The critical im- 

 portance of food availability at the initiation of 

 feeding capability was demonstrated 2 days later 

 when fed larvae contain almost lOO'^'i more RNA 

 and 55'''f more protein than larvae held in filtered 

 seawater. 



The RNA-DNA ratio was the most reliable and 

 sensitive index of nutritional state evaluated in 

 this study which included relationships between 

 RNA, DNA, protein, standard length, and dry 

 weight. RNA content was the most labile, decreas- 

 ing within 2 days after removal of food. DNA con- 

 tent was generally conserved except in the final 

 stages of starvation prior to death. The protein- 

 DNA ratio, which is an index of the amount of 

 protein per cell, generally decreased as starvation 

 progressed and the protem-RNA ratio generally 

 increased. The RNA-DNA ratio was particularly 

 useful as an indicator of condition since unlike 

 other indices it fell within well-defined limits 

 throughout most of the period studied. Winter 

 flounder larvae established a mean RNA-DNA 

 ratio of between 4.0 and 4.8 3 wk after initiation of 

 feeding (Figure 2). This range is similar to the 

 RNA-DNA ratio values reported by Bulow ( 1970) 

 for golden shiners. The RNA-DNA ratio was not 

 greatly affected by either the age or size of the 

 larvae until metamorphosis when the RNA-DNA 

 ratio increased to between 5.3 and 5.7 and re- 

 mained at this level until the experiment was 

 terminated on day 58 (Table 2). This is particu- 

 larly important since the age of sea-caught larvae 

 is difficult, if not impossible, to establish and a 

 large size range is observed in larvae of the same 

 age. This point was demonstrated on day 36 when 

 a large mortality of smaller larvae resulted in an 

 increase in the mean DNA. RNA, and protein con- 



tent of starved larvae. The RNA-DNA ratio, how- 

 ever, was unaffected by the change in size dis- 

 tribution and continued to decrease. Results from 

 larvae transferred to filtered seawater 18 h prior 

 to sampling and allowed to empty their stomachs 

 (Table 1) indicate that the RNA-DNA ratio is not 

 significantly affected by stomach contents at the 

 time of sampling. 



The RNA-DNA ratios of winter flounder larvae 

 captured in Narrow River fell within the range of 

 values observed for fed winter flounder in the 

 laboratory. The high RNA-DNA ratios indicated 

 that the larvae were in good nutritional condition. 

 This observation is supported by visual examina- 

 tion of the larvae and the high growth and survi- 

 val rates of laboratory-reared winter flounder held 

 in situ in Narrow River with a semiopen environ- 

 mental chamber (Laurence et al. 1979). 



Before measurements of RNA-DNA ratios are 

 useful in the field, the effect of changing environ- 

 mental conditions such as temperature, salinity, 

 and possibly various pollutants as well as low prey 

 concentrations and intermittent feeding should 

 be evaluated. Although adult golden shiners, lar- 

 val winter flounder, and larval cod, Gadiis 

 morhua, (Buckley unpubl. datal showed a similar 

 decline in RNA-DNA ratio when food is withheld, 

 the response of other species should be deter- 

 mined. 



.•\c k 111 1 \\ letlg mc n[ s 



I would like to thank G. C. Laurence and E 

 Jackim for their critical review of the manuscript. 



Lit(.-r.iturc ( ituil 



BL.AXTEK, J. H .S 



1971. Feeding and condition of Clyde herring lar 

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1970. RNA-DNA ratios as indicators of recent growth 

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1952 A microchemical determination of desoxyribonu- 

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1974a. Chemical changes during growtli and starvation oi 

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