FISHERY BULLETIN: VOL. 75, NO. 3 



0.0 100.0 200.0 300.0 100.0 500.0 600.0 700.0 800.0 300.0 1000.0 1100.0 

 0RY HEIGHT c)JG> 



FIGURE 10. — Daily food requirements of winter flounder larvae 

 at 8°C over the range of dry weight from hatching to metamor- 

 phosis and at different planktonic prey concentrations. Numbers 

 for each simulation indicate prey concentration in calories per 

 liter; 6.7-21.7 simulations are in ascending order from top 

 to bottom. 



v «0.0 



. 1 1 1 1 1 1 1 ' 



0.0 100.0 200.0 300.0 100.0 500.0 600.0 700.0 800.0 300.0 1000.0 

 DRr HEIGHT ipG> 



FIGURE 12. — Regression relationships of percentages of nauplii 

 and older stage copepods eaten by winter flounder larvae of 

 different sizes at 8°C. 



B.O 



3 



1.0 « 



. K 



IS 



3 



0.0 lOO.O 700.0 100.0 000.0 500.0 600.0 700.0 100.0 300.0 1000.0 1100. 1700.0 

 DRY HEIGHT (JJG) 



FIGURE ll. — Predicted number of nauplii or older stage cope- 

 pods required for daily consumption by winter flounder larvae 

 at 8°C over the range of dry body weights from hatching to 

 metamorphosis and at different planktonic prey concentrations. 

 Numbers for each simulation indicate prey concentration in 

 calories per liter; 6.7-21.7 simulations are in ascending order 

 from top to bottom. 



older stage copepods as larval size increases 

 (Figure 12). 



The percentage of body weight consumed per 

 day index (Figure 13) demonstrated sharply de- 

 creasing values during the first weeks of life (10- 

 75 fig), after which values remained fairly stable 

 until metamorphosis. More food was consumed 

 per body weight at lower plankton densities. The 

 differences became minimal with increasing 

 plankton density. 



Predicted gross growth efficiencies increased 

 sharply from first feeding until a dry body weight 

 of 100 fig, after which they continued to increase 

 but at a decelerated rate (Figure 14). Efficiencies 

 were lower at lower plankton concentrations, and 

 the differences became smaller as plankton con- 

 centration increased. 



DISCUSSION 



A majority of the prior research has dealt with 

 instantaneous estimates of larval food needs 

 (Chiba 1961; Braum 1967) rather than a descrip- 

 tive relationship over the range of larval sizes 

 from hatching to metamorphosis. Larval winter 

 flounder exhibited a linear increase in food con- 

 sumption, as indicated by stomach contents with 

 increasing size (Figure 1). A linear relationship 

 was also reported for larval largemouth bass, 

 Micropterus salmoides (Laurence 1971b). Stepien 

 (1974) observed an exponential increase for the 

 larvae of sea bream, Archosargus rhombodalis, at 

 much higher temperatures (23°-29°C) than the 

 8°C studied for winter flounder in this research. 



The amount of food a larval fish consumes dur- 

 ing a day depends on the size of the fish and den- 

 sity of the prey organisms available (Ivlev 1961a, 

 b). This is especially evident for winter flounder 

 larvae for which the traditional Ivlev relationship 

 changes with age or size (see Prey Density and 

 Intensity of Feeding, Figure 2). Smaller, younger 

 larvae reached maximum ration (R, Equation (7)) 



538 



