Tilapia fry perform similarly under varied photoperiods
Studies point to energy savings
As tilapia culture expands worldwide, more indoor hatcheries are being built to improve management and control environmental conditions during this early growth phase. Biosecurity is greatly increased in indoor hatcheries, but so is the energy cost associated with the operation of these facilities.
The authors recently carried out experiments to study the effects of photoperiod on the growth and survival of Oreochromis species red tilapia fry and evaluate if light energy costs could be decreased.
Three 30-day experiments were conducted under laboratory conditions simulating the hatchery phase. Fry were fed to satiation 9 times/day, every two hours from 6 a.m. to 10 p.m. in experiments 1 and 2, and six times/day, every three hours from 7 a.m. to 10 p.m. in experiment 3. A commercial feed containing 45 percent protein, 5 percent fat and 3 percent fiber was used. Values for water ammonia, nitrites, nitrates and pH where maintained within the appropriate ranges for the species by batch water exchange when needed.
Experiment 1
Three photoperiods with three replicates each were tested: 16 hours of constant light and eight hours dark (16L:8D); eight hours of constant light, eight hours with light turned on for 15 minutes at each feeding time and eight hours dark (8L:8I:8D); and eight hours light and 16 hours dark (8L:16D). The light source was 35-watt fluorescent tubes with an average intensity of 1,450 lux at the water surface.
Fry with an average initial weight of 0.011 grams were stocked in plastic tanks with 40 liters of freshwater at a density of 1.25 fry/L. The average water temperature was 26.3 degrees-C and average dissolved-oxygen concentration was 7.2 ppm. No significant differences among survivals or final weights were detected (Table 1).
Alvarez-Rosario, Performance of tilapia at three different photoperiods, Table 1
| Treatment | Initial Weight (g) | Final Weight (g) | Survival (%) |
|---|---|---|---|
| 16L:8D | 0.011 | 0.584 | 87.3 |
| 8L:8I:8D | 0.011 | 0.613 | 82.0 |
| 8L:16D | 0.011 | 0.564 | 75.3 |
Experiment 2
Three photoperiods with four replicates each were tested: 16 hours constant light and eight hours dark (16L:8D), 16 hours of light turned on for 15 minutes at each feeding time and eight hours dark (16I:8D); and eight hours light and 16 hours dark (8L:16D). More 35-watt fluorescent tubes were used than in experiment 1 to achieve an average intensity of 2,094 lux at the water surface.
Fry with an average initial weight of 0.016 grams were stocked in plastic tanks with 45 liters of freshwater at a density of 1.55 fry/L. Average water temperature and dissolved oxygen were 27.0 degrees-C and 6.9 ppm, respectively. No significant differences among survivals or final weights were detected (Table 2).
Alvarez-Rosario, Performance of tilapia at three different photoperiods, Table 2
| Treatment | Initial Weight (g) | Final Weight (g) | Survival (%) |
|---|---|---|---|
| 16L:8D | 0.016 | 0.442 | 75.7 |
| 16I:8D | 0.016 | 0.372 | 71.9 |
| 8L:16D | 0.016 | 0.437 | 73.9 |
Experiment 3
Five photoperiods with four replicates each were tested: 24 hours of constant light (24L), 15 hours constant light and nine hours dark (15L:9D), 15 hours of light turned on for 15 minutes at each feeding time and nine hours dark (15I:9D), nine hours of light provided for 15 minutes at each feeding time and 15 hours dark (9I:15D), and 24 hours of darkness (24D). As in experiment 2, fluorescent tubes delivered an average intensity of 2,094 lux at the water surface.
Fry with an average initial weight of 0.044 grams were stocked in plastic tanks with 50 liters of freshwater at a density of 1.10 fry/L. Average water temperature and dissolved-oxygen concentration were 27.7 degrees-C and 5.1 ppm, respectively. No significant differences among survivals or final weights were detected (Table 3).
Alverez-Rosario, Performance of tilapia at five different photoperiods, Table 3
| Treatment | Initial Weight (g) | Final Weight (g) | Survival (%) |
|---|---|---|---|
| 24L | 0.044 | 1.152 | 95.9 |
| 15L:9D | 0.044 | 1.185 | 92.7 |
| 15I:9D | 0.044 | 1.394 | 93.6 |
| 9I:15D | 0.044 | 1.388 | 95.0 |
| 24D | 0.044 | 1.178 | 90.0 |
(Editor’s Note: This article was originally published in the March/April 2009 print edition of the Global Aquaculture Advocate.)
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Authors
-
Science and Technology Department
Universidad Metropolitana
P. O. Box 21150
San Juan, Puerto Rico 00928-1150 USA -
Science and Technology Department
Universidad Metropolitana
P. O. Box 21150
San Juan, Puerto Rico 00928-1150 USA -
Science and Technology Department
Universidad Metropolitana
P. O. Box 21150
San Juan, Puerto Rico 00928-1150 USA -
MARNETEC S.L.
Barcelona, Spain
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