LAURENCE: BIOENERGETIC MODEL FOR WINTER FLOUNDER LARVAE 



pirometers) and techniques (Umbreit et al. 1964) 

 were used to measure oxygen consumption for 

 metabolic determinations in relation to tempera- 

 ture and larval size. A description of the specific 

 methods and results has been reported earlier 

 (Laurence 1975). 



All combustions for caloric determinations of 

 larval winter flounder tissue were done in tripli- 

 cate in a Parr 1241 automatic adiobatic calori- 

 meter adapted for a microbomb. Caloric values for 

 copepod prey species and methodology for these 

 determinations are reported by Laurence (1976). 



All statistical analyses used in this research are 

 described in Steel and Torrie (1960) and Draper 

 and Smith (1966). Modeling and analyses were 

 done in the FORTRAN IV language on an IBM 

 370 computer. 



EXPERIMENTAL RESULTS 



Food Consumed and Relationship 

 to Larval Size 



Numerical analysis of stomach contents is not 

 very meaningful in itself. It can, however, be 

 useful in conjunction with the measurement of 

 other parameters. An estimation of the dry weight 

 and caloric value of food consumed per larval 

 dry weight was needed as part of the overall bio- 

 energetic model. Stomach analysis by enumerat- 

 ing copepods in larvae fed high concentrations 

 (2 or 3 nauplii/ml) combined with information on 

 dry weights and caloric values of the copepods 

 provided this. Mean dry weights for the copepod 

 species and life stage were taken from the litera- 

 ture (Conover 1960; Anraku 1964; Hargrave and 

 Geen 1970; Gaudy 1974). Caloric values were 

 determined in our laboratory (Laurence 1976). 

 The average composite values used for the cope- 

 pods in this study were 1.3 /u-g dry weight for 

 nauplii, 15.4 fig dry weight for older stages, and 

 5,251 cal/g dry weight for all copepod tissue. Mul- 

 tiplying the numbers of plankton species and life 

 stage per stomach by the average dry weight val- 

 ues for each plankter type and summing yielded 

 the mean dry weight of the stomach contents. 

 Results of these analyses along with nauplii to 

 older stage ratios of copepods consumed and calor- 

 ic value per stomach are shown in Table 1. The 

 regression relationship of the logarithms of larval 

 dry body weight and larval stomach contents 

 weight was positively linear (Figure 1) and sig- 

 nificantly correlated (R = 0.87, P = 0.01). 



TABLE 1. — Mean numbers, weights, and caloric values of cope- 

 pods consumed by larval winter flounder of different sizes. Each 

 sample consists of 25 larvae. 



Mean larval 



dry wt 



(Mg) 



Mean no. of 



copepods per 



stomach 



Naupllus to 



older stage 



ratio 



Mean dry wt 



per stomach 



(M9) 



Calorie 



per 

 stomach 



LflRVSL DRY HEIGHT <UG> 

 10,0.0 



LOG IflRVHl DRY HEIGHT <UG) 



FIGURE 1. — The regression relationship of larval dry body 

 weight to larval stomach contents weight for winter flounder 

 at 8°C. 



Prey Density and Intensity 

 of Feeding 



The relationship between intensity of feeding 

 and concentration of prey is important in deter- 

 mining food intake. Ivlev (1961b) has analyzed 

 this relationship and expressed it by the following 

 function: 



4 L = oc{R - r) 

 dp 



where r = size of a unit ration for a unit time 



R = maximum size of the ration during the 

 same unit time at the upper limiting 

 level of food concentration beyond 

 which ration size does not increase 



531 



