Riley et al : Development and growth of hatchery-reared larval Trachinotus carolmus 
325 
Figure 6 
Back-calculated total length at age for hatchery-reared Florida 
pompano ( Trachinotus carolinus) larvae collected from three spawn- 
ings. Each curve represents measurements collected from 200 fish. 
Larvae from the third trial were significantly larger after seven 
days (P=0.007). 
a> 
•p 
(5 
"D 
c 
.2 
55 
Figure 7 
Back-calculated standard length at age for hatchery-reared 
Florida pompano (Trachinotus carolinus) larvae collected from 
three spawnings. Each curve represents data collected from 
200 fish. Larvae from the third trial were significantly larger 
after nine days (P<0.001). 
artificial feed or Artemia spp. at first feeding. 
In nature, larval Florida pompano prey upon 
a wide variety of different types and sizes of 
zooplankton. Larvae have small mouths with 
limited yolk reserves and undeveloped diges- 
tive systems at first feeding. As a consequence, 
larvae require small, slow-moving prey that are 
recognizable as potential food items. Given that 
the optimal prey size for marine fish larvae is 
25% of mouth gape at first feeding and increases 
to 50% within a few days (Hunter and Lasker, 
1981), the production of appropriate size live 
feeds must be considered an essential component 
of larviculture protocols. 
The marine rotifer, B. plicatilis (so-called large 
or small morphotypes), is the most commonly 
cultured and mass produced species of zooplank- 
ton worldwide (Yoshimura et al., 1996; Lubzens 
et al., 2001). Recent studies have shown that the 
strain and morphotypes of rotifer stocks within 
a hatchery can vary greatly, and rotifer stocks 
from commercial hatcheries often represent a 
mixture of species, strains, and morphotypes 
(Papkostas, 2006). Commercial hatcheries fre- 
quently buy or trade rotifer cultures with other 
hatcheries to meet production quotas, which can 
exceed one billion rotifers per day (Lubzens, 
2001). In this study, we used image analysis to docu- 
ment the size distribution of rotifers obtained from 
local hatcheries. Image analysis coupled with routine 
sampling allowed us to monitor growth, reproduction, 
and size-frequency distribution of rotifer stocks. De- 
termination of rotifer size-frequency distributions was 
useful for ensuring that a sufficient number of small 
individuals were available for first feeding larvae. Al- 
though rotifer strains and size distributions differed 
among years, there is little evidence that larval growth 
and survival was affected. Although production meth- 
ods for marine rotifers and Artemia spp. are currently 
