Brightman et al.: Energetics of larval Sciaenops ocellatus 
437 
Growth rates for pond-raised red drum larvae (Fig. 
2) were far greater than those for larvae fed rotifers 
in the laboratory, owing almost certainly to the 
greater prey diversity in the ponds. Larvae raised at 
25°C in the ponds increased in size an average of 
81.9 pg/day over 14 days: a 47.2 %BM/d increase. 
Larvae raised at 32°C in the ponds increased an av- 
erage of 799.22 mg/day: a 60.2 %BM/d increase; an 
increase of 10°C in the pond environment resulted 
in a two- to three-fold increase in absolute daily mass 
gain. 
Proximate and elemental composition of 
prey 
Brachionus plicatilis raised on Chlorella exhibited a 
protein level of 32.71% and a lipid level of 9.37% of 
its ash-free dry mass (AFBM). Carbohydrate level 
was low, averaging 2.84% (AFDM). The unrecovered 
mass was assumed to be due to refractory structural 
molecules that were not assayed for, e.g. chitin. Us- 
ing a figure of 0.24 pg for average individual bio- 
mass (Hoff and Snell, 1987) and the caloric values 
for protein, lipid, and carbohydrate of Brett and 
Groves (1979, see methods section), we suggest that 
each rotifer has an average energetic value of 
0.000526 calories. 
Elemental composition of the rotifers showed that 
the percent carbon was 42.02 %AFBM and the per- 
cent nitrogen was 10.41 %AFBM. The carbon-nitro- 
gen ratio was 3.56:1. 
Proximate and elemental composition of 
larvae 
Proximate composition can be expressed in three 
ways: as a percent of wet mass (%WM), a percent of 
ash-free dry mass (%AFBM), and as the total con- 
tent per larva (mg/individual). Table 1 shows the 
changes in proximate composition (%WM and 
%AFBM) as a function of ration level and age of the 
larvae; total content (mg/individual) is reported be- 
low in the text. 
Red drum eggs exhibited large water content (94.65 
%WM), a high protein content (42.17 %AFBM) and 
an intermediate lipid content (19.35 %AFBM)(Table 
1 ). Carbohydrate, generally an extremely small frac- 
tion of the overall proximate composition of marine 
species, proved to be so in this case as well (0.47 
%AFBM). 
Viewed as a fraction of the total body mass of each 
larva, the protein level (%AFBM) shows an increase 
through time at zero ration (43.84% to 62.47%) ac- 
companied by a reduction in lipid ( 19.72% to 13.29%), 
which indicates that, in starving larvae, lipid was 
used in preference to protein for energy production. 
On a pg/individual basis, protein actually decreased 
in starved larvae from 8.44 pg/individual in newly 
hatched larvae to 4.07 pg/individual for 6-day-old 
starved larvae (Table 2). Lipid values declined from 
2.59 pg/individual on day 3 to 0.87 pg/individual on 
day 6. Percent water remained high until death at 
day 6, averaging 91.0% throughout the survival period. 
Table 2 
Protein content, protein growth, RNA:DNA, and LDH in red drum larvae. Protein content was calculated from values reported in 
Table 1. Where values for % protein or % ash-free dry mass were missing, nearest neighbor values were used. Protein growth 
was calculated as described in text. RNA:DNA values are the mean for all RNA:DNA measurements within the last 2 d of the age 
interval shown in the table. They are reported as mean ±SD (n). Values for the 25°C pond were taken at day 7 instead of day 6 
and calculated accordingly. All (6-14) day RNAiDNA values are significantly different (P<0.05, Students t ). nd = no data 
Day 
2 
6 
10 
14 
2-6 
6-10 
10-14 
2-14 
6-14 
6 
10 
14 
6-14 
6 
10 
14 
Protein (ug/indiv) 
Protein growth (%/d) 
RNAiDNA 
LDH (units/gWM) 
Starved 
8.44 
4.07 
nd 
nd 
-18.20 
nd 
nd 
nd 
nd 
0.68+0.35 
(14) 
nd 
nd 
nd 
7.48 
nd 
nd 
5/mL at 2°C 
7.66 
7.55 
9.29 
16.34 
-0.40 
5.20 
14.10 
63.00 
9.50 
1.5110.43 
(6) 
1.4510.24 
(4) 
1.4910.14 
(4) 
1.5010.30 
(14) 
9.19 
14.44 
19.69 
5/mL at 25°C 
9.36 
9.77 
14.80 
47.33 
1.10 
10.40 
29.10 
13.50 
19.70 
1.1510.20 
(2) 
1.1910.32 
(3) 
1.2610.19 
(7) 
1.2510.21 
(12) 
15.06 
24.33 
33.60 
Pond 25°C 
8.16 
15.00 
67.70 
484.30 
12.10 
50.20 
49.20 
34.00 
49.60 
2.8910.51 
(4) 
3.0610.81 
(4) 
3.5610.27 
(2) 
3.0910.62 
(10) 
18.94 
30.86 
42.78 
Pond 32°C 
8.51 
82.20 
324.60 
1,116.20 
56.70 
34.30 
30.90 
46.00 
32.60 
1.19 
2.21 
1.39 
1.6010.54 
12.69 
19.44 
26.19 
