Riley et al.: Development and growth of hatchery-reared larval Trachmotus carolmus 
319 
values approximate the necessary quantities needed for 
mass production. The advent of new broodstock man- 
agement techniques for domestication and controlled 
reproduction in captivity offer great promise for the 
culture of Florida pompano. However, there is a need 
to develop and refine hatchery technologies for this spe- 
cies because larvae undergo major functional and mor- 
phological changes throughout their early life history. 
Florida pompano eggs are typical of marine fishes 
with pelagic eggs. In a single spawning event, one fe- 
male can produce 200,0000 to 400,000 small, buoy- 
ant eggs that range in size from 0.87 to 1.00 mm in 
diameter (Hoff et al., 1978a). Florida pompano eggs 
normally have a single oil globule, although eggs from 
some broodfish reportedly have several small oil glob- 
ules. The size and number of oil globules within eggs 
can serve as an indicator of egg quality and correlate 
with the amount of energy available for developing lar- 
vae (Barbaro et al., 1991). The yolk that is deposited 
during vitellogenesis must provide nutrition for the 
developing embryo and larvae. Newly hatched Florida 
pompano larvae are approximately 2.0 mm TL and are 
not well developed (Hoff et al., 1978b). Depending on 
water temperature and developmental rates, larvae 
use yolk reserves for two to three days after hatching 
(DAH), which coincides with pigmentation of the eyes, 
mouth formation, and first feeding. Florida pompano 
larvae have been cultured by using a variety of live 
zooplankton, including copepods, rotifers, and Artemia 
spp. Florida pompano undergo metamorphosis at 24 
DAH at 15 mm TL and can easily transition to dry 
feeds (McMaster, 1988). 
Previously published descriptions of Florida pom- 
pano larvae provide limited details on development 
and growth under hatchery conditions. To improve the 
understanding of larval development of this species, the 
present study was conducted to measure the growth of 
larvae from hatching through metamorphosis by using 
digital photography and image analysis. The specific 
objectives were 1) to compare morphological variation 
among larvae from three different spawning trials; 
2) to document time of occurrence for critical periods 
including first feeding, yolk and oil globule exhaustion, 
gas bladder inflation, transition in diet, and onset of 
metamorphosis; and 3) to develop a model feeding re- 
gime for Florida pompano larvae. 
Materials and methods 
Spawning and egg incubation 
This study presents data regarding developmental char- 
acteristics and growth of larvae obtained from captive 
reproduction of Florida pompano broodstock held at the 
U.S. Department of Agriculture, Agricultural Research 
Service (USDA-ARS) Center for Reproduction and Lar- 
viculture in Fort Pierce, Florida (Weirich and Riley, 
2007). Broodstock (sex ratio, 1:1) were held in recirculat- 
ing tank systems under controlled photothermal condi- 
tions and were sampled periodically to assess health 
and reproductive condition. To initiate spawning, ripe 
females (mean oocyte diameter >500 pm) and males were 
implanted with a 75 -pg slow-release pellet of gonadotro- 
pin-releasing hormone analogue (Syndel International, 
Inc., Vancouver, BC). Fish spawned volitionally approxi- 
mately 36 hours after hormone implantation, and eggs 
were collected and stocked into aerated 100-L incuba- 
tion tanks (24-26°C). Hatching occurred approximately 
30-36 hours after fertilization. 
Larval culture 
In three independent larval rearing trials (initiated 15 
June 2004, 17 June 2004, 17 August 2005), approxi- 
mately 50,000 larvae (0 DAH) were stocked into a 1.0-m 3 
round fiberglass tank. The tank was filled with 800 L 
of natural seawater that had been subjected to biologi- 
cal and mechanical filtration, in addition to ultraviolet 
sterilization, before use. Water quality was monitored 
daily with a multiparameter dissolved oxygen probe (YSI 
Incorporated, Model 85, Yellow Springs, OH). Water was 
not exchanged from zero DAH through five DAH. After 
five DAH, water quality was maintained by daily water 
changes ranging from 50% to 200% through 20 DAH. 
Although similar production methods were used dur- 
ing each year of the study, trials were conducted within 
a greenhouse during the first year of the study and 
within an insulated, climate-controlled hatchery dur- 
ing the second year. After stocking, tanks were gently 
aerated and surface light levels were maintained at 300 
lux (model LI-189, LI-COR, Lincoln, NE) for 16 hours 
daily. At two DAH, the aeration level was increased, 
tanks were inoculated with cultured microalgae ( Nan - 
nochloropsis oculata) (Instant Algae, Reed Mariculture, 
Campbell, CA) to maintain green water culture condi- 
tions, and surface light levels were increased to 2000 or 
3000 lux. Larvae were fed enriched rotifers ( Brachionus 
plicatilis; 53-225 pm) from two DAH through 15 DAH. 
Rotifer strains and size distributions differed among 
years (Fig. 1). Larvae were fed Artemia spp. nauplii 
(-480 pm) from 12 DAH through 20 DAH (Embryon, 
INVE, Salt Lake City, UT). Live feed organisms were 
fed three times daily and were maintained at densi- 
ties of one to three individuals per mL. Artificial feed 
(400-800 pm diameter particles) was offered to larvae 
beginning at 10 DAH (INVE NRD Micro Pellet, Salt 
Lake City, UT). 
Sample collection 
Samples of 10 larvae were randomly collected daily from 
hatching through completion of metamorphosis at 20 
DAH. Larvae were euthanized by brief immersion in cold 
seawater (4°C), placed on glass slides, and photographed 
by using a dissecting microscope at 4x magnification. A 
compound microscope at 100 x magnification was used 
to photograph the head and mouth of each larva from 0 
DAH through 5 DAH; thereafter, the head and mouth 
of each larva was photographed by using the dissect- 
