Effects of photoperiod on the performance of farmed Nile tilapia Oreochromis niloticus I. Growth, feed utilization efficiency and survival of fry and fingerlings.pdf

7/26/2019 Effects of photoperiod on the performance of farmed Nile tilapia Oreochromis niloticus I. Growth, feed utilization e

1/10

Effects of photoperiod on the performance of

farmed Nile tilapia Oreochromis niloticus:

I. Growth, feed utilization efficiency and survival

of fry and fingerlings

Abdel-Fattah M. El-Sayed*, Mamdouh Kawanna

Department of Aridland Agriculture, College of Food Systems, United Arab Emirates University,

Al Ain, United Arab Emirates

Received 16 May 2003; received in revised form 5 November 2003; accepted 7 November 2003

Abstract

The effect of photoperiod on survival, growth rates and feed utilization efficiency of Nile

tilapia (Oreochromis niloticus L.) fry and fingerlings was investigated in two consecutive

experiments. In Experiment 1, triplicate groups of 75 swim-up fry (0.02 g) were stocked in 25-l

fiberglass tanks, in recirculating indoor system. The fish were exposed to four photoperiod

(light:dark, L:D) cycles (24L:0D, 18L:6D, 12L:12D and 6L:18D). Light intensity was kept

constant at 2500 lx throughout the study. The fish were fed a tilapia diet (35% crude protein, 350

kcal GE/100 g) at a daily rate of 3020% BW, three times a day for 60 days. The best weight

gain, specific growth rate (SGR), feed efficiency and fish survival were achieved at 24L:0D and

18L:6D, without significant differences between them. Fry performance was significantly retarded

by reducing light phase (12L:12D and 6L:18D). In the second experiment, triplicate groups of 40

fingerlings (mixed sexes) (2.4F

0.05 g) were stocked in 0.4-m

3

fiberglass tanks and exposed tothe same light intensity and photoperiod cycles used in Experiment 1. The fish were also fed the

same diet used in Experiment 1, at 5 4% BW/day, three times a day for 90 days. The fish

performance was not significantly affected by photoperiods. These results revealed that Nile tilapia

fry, but not fingerlings, reared in indoor, recirculating systems are significantly affected by

photoperiod. The insignificant difference in fry performance between 24L:0D and 18L:6D groups

suggests that a 18L:6D cycle be used in case of larval rearing, while shorter light phases are

0044-8486/$ - see front matterD 2004 Elsevier B.V. All rights reserved.

doi:10.1016/j.aquaculture.2003.11.012

* Corresponding author.

E-mail address:[email protected] (A.-F.M. El-Sayed).

www.elsevier.com/locate/aqua-online

Aquaculture 231 (2004) 393402


2/10

suggested for optimal growth, feed efficiency and survival of fish fingerlings, taking into

consideration the cost of electricity.

D 2004 Elsevier B.V. All rights reserved.

Keywords:Photoperiods; Nile tilapia; Fry; Fingerlings; Growth; Feed efficiency; Survival

1. Introduction

Tilapiaare the third most important cultured fish group in the world, after carps and

salmonids(FAO, 2002).Tilapia culture is also one of the fastest growing farming activities,

with an average annual growth rate of 13.4% during 19701999(FAO, 2002).As a result,

the production of farmed tilapia has increased from 383,654 mt in 1990 to 1,265,780 mt in

2000 (FAO, 2002). During the same period, the value of these fish has increased from

US$515.2 million to US$1706.5 million. Nile tilapia is by far the most important farmed

tilapia species in the world. The production of farmed Nile tilapia reached 1,045,100 mt in

2000, representing 82% of total production of farmed tilapia, with a value of US$1250.4

million(FAO, 2002).

The intensive culture of tilapia under controlled management systems is widely

expanding to meet the increasing demands for these fishes, especially in developing

countries. In this regard, the use of closed culture systems has received a considerable

attention, and is becoming more common worldwide, particularly in arid areas that faceshortage in fresh water or brackish water, or in areas where environmental parameters, such

as salinity and temperature, are outside the tolerance range of tilapia(Muir et al., 2000).

Tilapia can tolerate a wide range of water temperature, dissolved oxygen (DO), salinity,

pH, light intensity and photoperiods. However, the determination of optimal environmental

conditions for cultured tilapia in closed systems is essential for the maximization of its

production, profitability and sustainability(Muir et al., 2000).The effects of most of these

factors on tilapia in different culture systems have been extensively studied (Kirk, 1972;

Chervinski, 1982; Philippart and Ruwet, 1982). However, our knowledge on the effect of

photoperiod on tilapia in recirculating culture systems is limited.

Photoperiod acts as an artificial Zeitgeber (cue or synchronizer), regulating the dailyendogenous rhythms in fish (Duston and Saunders, 1990; Biswas et al., 2002) and also

affects fish growth, locomotor activity, metabolic rates, body pigmentation, sexual

maturation and reproduction (Gross et al., 1995; Silva-Garcia, 1996; Boeuf and Le Bail,

1999; Trippel and Neil, 2002; Biswas and Takeuchi, 2002; Biswas et al., 2002). On the

other hand, the growth and metabolic rates of several other species were not significantly

affected by photoperiods (Imsland et al., 1995; Hallaraker et al., 1995; Purchase et al.,

2000). Meanwhile, photoperiod may positively affect larval stages, but not juvenile stages

(Barlow et al., 1995).

Tilapia are generally diurnal feeders, feeding at different times of the day. Yousuf

Haroon et al. (1998)found that feeding activity of tilapia hybrids (O. mossambicusO.niloticus) reared in ponds was continuous during daytime, with a single feeding peak at

around afternoon-dusk. Similar results have been reported with the same fish reared in a

A.-F.M. El-Sayed, M. Kawanna / Aquaculture 231 (2004) 393402394


3/10

closed system, where the maximum feeding activity occurred during the afternoon

(Zavyalov and Lavrovskii, 2001).In addition, Nile tilapia exhibit a regular diurnal feeding

rhythm with maximum feeding intensity between 5:00 and 8:00 a.m., and cease feeding

between 14:00 and 18:00 p.m.(Harbott, 1975).These studies clearly pointed out the role ofphotoperiod on feeding activity and growth of these fishes. However, few studies have

considered the effect of photoperiod on tilapia growth, feed efficiency and metabolism,

physiological functions and reproduction under controlled culture conditions (Ross and

McKinney, 1988; Lourenco et al., 1998; Ridha and Cruz, 2000; Biswas and Takeuchi,

2002; Biswas et al., 2002).

We conducted a series of experiments to investigate the effect of photoperiod on the

performance of Nile tilapia (Oreochromis niloticus) reared intensively in a recirculating

system. The present study was carried out in two consecutive experiments to address the

effects of photoperiod on the growth, feed utilization efficiency and survival of fry and

fingerling fish.

2. Materials and methods

2.1. Fish and culture facilities

Nile tilapia fry and fingerlings were produced from tilapia broodstock kept in captivity

in the aquaculture facility, College of Food Systems, United Arab Emirates University, Al-

Ain, UAE. The culture units consist of fiberglass tanks in a recirculating indoor system.The tanks were provided with central drainage pipes surrounded by outer sleeves pipes,

perforated at the bottom, to facilitate self-cleaning and waste removal. The culture system

was also provided with a biological filter (Plastic tubing structures), continuous aeration

through an air compressor (Hick Hargreaves, UK) and heaters, with thermostats, to keep

water temperature at 27 jC. About 10% of the water was replaced daily by new fresh

water with the same temperature. Water quality parameters, including DO (Oxygen meter,

YSI, model 58), ammonia (NH4-N), nitrates (NO3-N) and nitrites (NO2-N) (Orion

Aquafast, Germany) and pH (pH meter, Jenway, UK) were monitored weekly. The

average values of these parameters throughout the study were: DO = 6.7F 1.4 mg/l,

NH4-N = 0.053F 0.002 mg/l, NO3-N = 11.4F 1.32 mg/l, NO2V 0.05 mg/l andpH = 8.1F 0.06.

2.2. Experimental design

2.2.1. Experiment 1

The first experiment was designed to study the effect of photoperiod on growth rates,

feed utilization efficiency and survival of Nile tilapia fry. Triplicate groups of 75 swim-up

fry (0.02 g average weight) were stocked into 25-l rearing tanks (described in 2.1), with a

water flow rate of 1 l/m. The fish were exposed to four photoperiod (light:dark, L:D) cycles

(24L:0D, 18L:6D, 12L:12D and 6L:18D), using fluorescent lamps. Photoperiods werecontrolled by a 24-h timer (Multi 9, Merlingerin, Germany). Light intensity was kept

constant at 2500 lx throughout the study.

A.-F.M. El-Sayed, M. Kawanna / Aquaculture 231 (2004) 393402 395


4/10

The fish were fed an experimental diet (35% crude protein, 350 kcal GE/100 g) at a

daily rate of 30% BW/day, reduced to 20% BW/day at the beginning of the second

month (as recommended by El-Sayed, 2002), for 60 days. The diet was provided three

times a day at 8:00, 12:00 and 17:00 h, except for the 6L:18D group which was fedtwice a day at 8:00 and 13:00 h. All fish in each tank were weighed at 15-day

intervals, their average weights recorded, and the daily rations readjusted accordingly.

At the end of Experiment 1, all fish in each tank were netted, weighed and the average

final weights recorded. The undersized fingerlings were netted out and the rest of the

fish were transferred into 0.4-m3 fiberglass tanks (used in the second experiment)

having a water flow rate of 10 l/m. They were fed the test tilapia diet for a 10-day

acclimation period, to adapt them to the new tanks, stocking density and water flow

rate.

2.2.2. Experiment 2

The second experiment was conducted to investigate the effects of photoperiod on

survival, growth rates, feed utilization efficiency and survival of Nile tilapia fingerlings.

Forty fish of almost similar sizes were selected from each tank, weighed and their average

weight recorded (2.4F 0.05 g). Triplicate groups of fish were stocked in the 0.4-m3 tanks

and exposed to the culture conditions, light intensity and photoperiod cycles used in

Experiment 1.

The fish were fed the same diet used in Experiment 1, for 90 days, at a daily rate of 5%

BW/day (reduced to 4% BW/day at the beginning of the third month), three times a day

(8:00, 13:00 and 17:00 h), except for the 6L:18D group where the diet was offered twice aday at 8:00 and 13:00 h. All fish from each tank were weighed at 15-day intervals, their

average weights recorded, and daily rations readjusted accordingly. At the end of

Experiment 2, all fish in each tank were netted, weighed and their average final weight

recorded.

2.3. Statistical analyses

A one-way analysis of variance (ANOVA) was conducted to test the effect of

photoperiod on the growth rates, feed utilization efficiency and survival of fish fry and

fingerlings, using the computer program SPSS (SPSS Version 11.0.0, 2003). Leastsignificant difference (LSD) was used to compare means atP< 0.05, as described byGill

(1981).

3. Results

3.1. Experiment 1

The results of Experiment 1 indicated that photoperiod significantly affected fish

survival and growth performance (Table 1andFig. 1). The long light phases (24 and 18light hours) produced the best fish survival (89% and 85%), percentage weight gain (6050%

and 6100%), specific growth rate (% SGR) (6.87% and 6.88%) and feed conversion ratio



5/10

(FCR) (1.52 and 1.55), respectively. However, the difference between these two photo-periods was not significant (P>0.05). The growth and feed efficiency of fry were

significantly retarded by reducing light phase to 12 (P< 0.01) and 6 (P< 0.05) h.

Fig. 1. Effect of photoperiod on the growth of Nile tilapia fry.

Table 1

Effects of photoperiod on growth rates and feed utilization efficiency of Nile tilapia fry (meanFS.E.)

L:D cycle IW1 FW2 % Gain3 SGR4 FCR5 Survival (%)

24L:0D 0.02 1.23F 0.08a 6050F 376a 6.87F 0.16a 1.52F 0.12a 89F 3.60a

18L:6D 0.02 1.24F 0.09a 6100F 425a 6.88F 0.12a 1.55F 0.07a 85F 1.15ab

12L:12D 0.02 0.95F 0.09b 4650F 449b 6.42F 0.18b 1.78F 0.07ab 76F 3.84b

6L:18D 0.02 0.65F 0.07c 3150F 344c 5.80F 0.19c 1.85F 0.12b 78F 6.49ab

Values in the same column with different superscripts are significantly different (P= 0.05).1 Average initial weight (g/fish).2 Average final weight (g/fish).3 100(FW IW/IW).4 Specific growth rate = 100(ln FW ln IW)/time (days).5 Feed conversion ratio = dry feed given (g)/wet weight gain (g).



6/10

3.2. Experiment 2

On the contrary to Experiment 1, the results of Experiment 2 revealed that fish survival,

percentage weight gain, SGR and FCR of mixed-sex fingerling tilapia were not signifi-

cantly affected by photoperiod (P>0.05)(Table 2).

4. Discussion

It has been suggested that freshwater fish species aremore sensitive to photoperiod thanmarine and diadromous species (Imsland et al., 1995). However, the response of marine

species to photoperiods has been well investigated, while less information is available on

freshwater species.

The results of the present study indicated that the response of Nile tilapia to photoperiod

cycles depends on fish developmental stage. Tilapia fry were more sensitive to photoperiod

than fingerlings and juveniles. Fish fry subjected to long light periods (24 and 18 h) had

significantly better growth and feed utilization efficiency than those exposed to interme-

diate or short light periods (12 or 6 h). Similar results have been reported with several

marine fish larvae, where the growth rates were improved with increasinglight periods. The

growthof black porgyMylio macrocephalus(Kiyono and Hirano, 1981), seabreamSparusaurata(Tandler and Helps, 1985)and rabbitfishSiganus guttatus(Duray andKohno, 1988)

larvae was best under continuous light, while the growth of soleSolea solea(Fuchs, 1978),

European seabass Dicentrarchus labrax (Barahona-Fernandes, 1979), barramundi Lates

calcarifer(Barlow et al., 1995)and snapperPagrus auratus(Fielder et al., 2002)larvae was

better at 18 and 24 h light periods than at 12:12 h or shorter light periods.

One possible explanation of the retardation of growth and feed efficiency of tilapia fry

during shorter light periods in the present study is that during these short light phases

insufficienttime was available for the establishment of a robustrhythmicity, as has been

reported byBiswas and Takeuchi (2002)and Biswas et al. (2002). The effect of photoperiod

on synchronizing an endogenous rhythm to the external environment may also require moreenergy in the shorter light periods, leading to a reduction of somatic fish growth (Biswas

and Takeuchi, 2002; Biswas et al., 2002).

Table 2

Effects of photoperiod on growth rates and feed utilization efficiency (meanF S.E.) of fingerling Nile tilapia

L:D cycle IW1 FW2 % Gain3 SGR4 FCR5 Survival (%)

24L:0D 2.33F 0.09a 49.60F 1.67a 2024F 24.0a 3.40F 0.10a 1.22F 0.09a 95.0F 0.00a

18L:6D 2.43F 0.07a 51.35F 2.15a 2013F 88.5a 3.39F 0.11a 1.27F 0.14a 95.0F 5.00a

12L:12D 2.34F 0.10a 46.80F 2.71a 1900F 85.0a 3.33F 0.05a 1.32F 0.08a 95.0F 2.50a

6L:18D 2.44F 0.06a 46.00F 3.30a 1786F 110.0a 3.27F 0.07a 1.31F 0.13a 96.7F 2.50a

Values in the same column with different superscripts are significantly different ( P= 0.05).1 Average initial weight (g/fish).2 Average final weight (g/fish).3 100(FW IW/IW).4 Specific growth rate = 100(ln FW ln IW)/time (days).5 Feed conversion ratio = dry feed given (g)/wet weight gain (g).



7/10

The improvement in the performance of Nile tilapia fry in the present study with

increasing lightperiod may also have been related to the reduction of standard metabolic

rate. In support,Biswas et al. (2002)andBiswas and Takeuchi (2002)studied the effects of

photoperiod on the metabolic rate of fed and unfed young and adult Nile tilapia. They foundthat metabolic rate and energy loss were negatively correlated with light periods. They

concluded that Nile tilapia conserve energy when raised under photoperiods with longer

light phases. However, these authors suggested that growth studies must be conducted

under different photoperiod cycles in order to further evaluate the effects of photoperiod

regimes on these fish. The reduction of fishmetabolic rate with increasing light phases has

also been reported with marine fish species(Boehlert, 1981).

The present study demonstrated that the growth and feed efficiency of fingerling Nile

tilapia were not significantly affected by photoperiod. The significant effect of photoperiod

on larval stages, but notfingerling stages, has also been reported with several other species,

including soleS. solea(Fuchs, 1978),black porgyM. macrocephalus(Kiyono and Hirano,

1981), yellow tail flounder Pleuronectes ferruguineus (Purchase et al., 2000) and

barramundi L. calcarifer(Barlow et al., 1995).

In contrast to the present results, Lourenco et al. (1998) reported that Nile tilapia

fingerlings maintained on 14 h light had better weight gain than those reared at 10 h light.

This controversy may have been related to the differences in culture systems, fish size, sex

ratio and light type and intensity. It is clear that more work is needed to verify the effects of

photoperiods on different sized-tilapia. The improvement in performance of fish juveniles

with extended light phases has also been documented with several other species, including

Atlantic salmonSalmo salar(Saunders et al., 1985),Atlantic codGadus morhua(Folkvordand Ottera, 1993), turbotScophthalmus maximus(Imsland et al., 1995, 1997)and haddock

Melanogrammus aeglefinus (Trippel and Neil, 2002).

Tilapia are generally diurnal feeders in nature and under culture conditions. They feed at

different times of the day, depending on species and size. Harbott (1975)found that Nile

tilapia in Lake Rudolf (Uganda) exhibit a regular diurnal feeding rhythm with maximum

feeding intensity between 5:00 and 8:00 a.m., and cease feeding between 14:00 and 18:00

p.m. Diurnal feeding activity has also been reported in cultured tilapia.Yousuf Haroon et al.

(1998)found that feeding activity of tilapia hybrids (O. mossambicusO. niloticus) reared

in ponds was continuous during daytime, with a single feeding peak at around afternoon-

dusk. The maximum feeding activity ofO. niloticusO. mossambicushybrids reared in aclosed system occurred also during the afternoon Zavyalov and Lavrovskii (2001).

Feeding activity of Nile tilapia adults reared under conditions of self-feeding was also

observed exclusively during the light phases(Toguyeni et al., 1997).These studies clearly

pointed out the role of photoperiod on feeding activity and growth of these fishes.

Nile tilapia in the present study were fed the test diet three times per day, except for the

6L:18D group which was fed twice a day, due to the short light phase. During a 6-h light

period, feeding the fish three times (once every 2 h) may lead to feed waste, since the fish

may not accept the feed, as their stomachs will probably be still full from previous meals. In

addition, a number of studies indicated that feeding tilapia two to three times a day has

resulted in similar growth and FCR.Siraj et al. (1988)found that the best growth and FCRof red tilapia (O. mossambicusO. niloticus) fed at varying frequencies were attained at 2

and 3 feedings/day, and there was no significant difference between these two feeding



8/10

frequencies. Moreover,De Silva et al. (1986)found that the best performance of Nile tilapia

fingerlings fed a restricted ration at 3%/day was achieved at 1 or 2 feedings/day. Therefore,

one may argue that feeding frequency may have not significantly affected the present

results. Since fish fry and fingerlings were also given fixed rations (not ad libitum), at fixedtimes, it is unlikely that feed consumption has been directly affected by photoperiod.

Changing metabolic hormone activities as a result ofphotoperiods mayhave been the prime

factor affecting fish performance, as suggested byPorter et al. (2001).

In conclusion, the present results revealed that photoperiods significantly affect the

growth of Nile tilapia fry, but not mixed-sex fingerlings. A 18L:6D cycle was suggested for

optimal performance of fish fry, while shorter light phases could be used in case of fish

fingerlings, taking into consideration the cost of electricity. These results have a significant

application in tilapia aquaculture in indoor recirculating systems, as they improve our

understanding of the role that photoperiod plays in fish growth and metabolism. Adopting

the optimum photoperiod in case of tilapia fry will also reduce the amount of energy used

for standard metabolism, and in turn increase fish growth and profitability.

Acknowledgements

The authors thank Dr. Salih A. Al-Shorapy, Associate Professor of Animal Genetics,

Department of Aridland Agriculture, College of Food Systems, United Arab Emirates

University, for running the statistical analyses of the results.

References

Barahona-Fernandes, M.H., 1979. Some effects of light intensity and photoperiod on the sea bass larvae (Dicen-

ntrarchus labrax (L)) reared at the centre Oceanologique de Bretagne. Aquaculture 17, 311321.

Barlow, C.G., Pearce, M.G., Rodgers, L.J., Clayton, P., 1995. Effects of photoperiod on growth, survival and

feeding periodicity of larval and juvenile barramundi Lates Calcarifer(Bloch). Aquaculture 138, 159 168.

Biswas, A.K., Takeuchi, T., 2002. Effect of different photoperiod cycles on metabolic rate and energy loss of both

fed and unfed adult tilapia Oreochromis niloticus: Part II. Fish. Sci. 68, 543553.

Biswas, A.K., Endo, M., Takeuchi, T., 2002. Effect of different photoperiod cycles on metabolic rate and energy

loss of both fed and unfed young tilapia Oreochromis niloticus: Part I. Fish. Sci. 68, 465477.

Boehlert, G.W., 1981. The effects of photoperiod and temperature on laboratory growth of juvenile Sebastesdiploproaanda comparison with growth in the field. Fish. Bull. 79, 789794.

Boeuf, G., Le Bail, P., 1999. Does light have an influence on fish growth? Aquaculture 177, 129152.

Chervinski, J., 1982. Environmental physiology of tilapias. In: Pullin, R.S.V., Lowe McConnell, R.H. (Eds.), The

Biology and Culture of Tilapias. Proc. 7th ICLARM Conf., Manila, Philippines. International Center for

Living Aquatic Resources Management, Manila, Philippines, pp. 119128.

De Silva, S.S., Gunasekera, R.M., Keembiyahetty, R.M., 1986. Optimum ration and feeding frequency in

Oreochromis niloticus young. In: Mclean, J.L., Dizon, L.B., Hosillos, L.V. (Eds.), The First Asian Fisheries

Forum. Asian Fisheries Society, Manila, Philippines, pp. 559564.

Duray, M., Kohno, H., 1988. Effects of continuous lighting on growth and survival of first-feeding larval

rabbitfishSiganus guttatus. Aquaculture 109, 311321.

Duston, J., Saunders, R.L., 1990. The entrainment role of photoperiod on hypoosmoregulatory and growth-

related aspects of smolting in Atlantic salmon (Salmo salar). Can. J. Zool. 68, 707715.

El-Sayed, A.-F.M., 2002. Effects of stocking density and feeding levels on growth and feed efficiency of Nile

tilapia (Oreochromis niloticus L.) fry. Aquac. Res. 33, 621626.



9/10

Fielder, D.S., Bardsley, W.J., Allan, G.L., Pankhurst, P.M., 2002. Effect of photoperiod on growth and survival of

snapperPagrus auratus larvae. Aquaculture 211, 135150.

Folkvord, A., Ottera, H., 1993. Effects of initial size distribution, day length and feeding frequency on growth,

survival and cannibalism in juvenile Atlantic cod (Gadus morhua L.). Aquaculture 114, 243260.

Food and Agriculture Organization of the United Nations (FAO), 2002. FAO FishStat plus. Aquaculture Pro-

duction 19702000. Rome, Italy.

Fuchs, J., 1978. Influence de la photoperiode sur la croissance et la survie de la larve et du juvenile de sole ( Solea

solea) en elevage. Aquaculture 15, 6374.

Gill, J.L., 1981. Design and Analysis of Experiments in Animal and Medical Sciences, vol. VI. The Iowa State

Univ. Press, Ames, IA, U.S.A, p. 409.

Gross, W.L., Roelofs, E.W., Fromm, P.O., 1995. Influence of photoperiod on growth of green sunfish, Lepomis

cyanellus. J. Fish. Res. Board Can. 22, 13791386.

Hallaraker, H., Folkvord, A., Stefansson, S.O., 1995. Growth of juvenile halibut (Hippoglossus hippoglossus)

related to temperature, day length and feeding regime. Neth. J. Sea Res. 34, 139147.

Harbott, B.J., 1975. Preliminary observations on the feeding of Tilapia nilotica Linn. Lake Rudolf. Afr. J.

Hydrobiolog. Fish. 4, 2737.Imsland, A., Folkvord, A.F., Steffansson, S.O., 1995. Growth, oxygen consumption and activity of juvenile

turbot (Scophthalmus maximus) reared under different temperatures and photoperiods. Neth. J. Sea Res. 34,

149159.

Imsland, A.K., Folkvord, A.F., Jonsdottir, O.D.B., Steffansson, S.O., 1997. Effects of exposure of extended

photoperiods during the first winter on long-term growth and age at first maturity in turbot (Scophthalmus

maximus). Aquaculture 159, 125 141.

Kirk, R.G., 1972. A review of recent development in tilapia culture with special reference to fish farming in the

heated effluents of power stations. Aquaculture 1, 4660.

Kiyono, M., Hirano, R., 1981. Effects of light on the feeding and growth of black porgy, Mylio macro-

cephalus (Basilewsky) postlarvae and juveniles. Rapp. P-V. Reun.-Comm. Int. Explor. Sci. Mer Mediterr.

178, 334336.

Lourenco, J.N.P., Vicentini-Paulino, M.L.M., Delicio, H.C., 1998. Influence of photoperiod on the growth andgain of weight in Nile tilapia Oreochromis niloticus, under constant temperature in the two seasons. In:

Valenti, W.C., Zimmermann, S., Poli, C.R., Bassanesi Poli, A.T., Moraes, F.R., de Volpato, G., Camara,

M.R. (Eds.), Proc. Aquaculture Brazil 98. Sustainable Development, vol. 2, pp. 561569.

Muir, J., Van Rijn, J., Hargreaves, J., 2000. Production in intensive and recycle systems. In: Beveridge,

M.C.M., McAndrew, B.J. (Eds.), Tilapias: Biology and Exploitation. Kluwer Academic Publishing, Great

Britain, pp. 405445.

Philippart, J.C., Ruwet, J.C., 1982. Ecology and distribution of tilapias. In: Pullin, R.S.V., Lowe McConnell, R.H.

(Eds.), The Biology and Culture of Tilapias. Proc. 7th ICLARM Conf., Manila, Philippines. International

Center for Living Aquatic Resources Management, Manila, Philippines, pp. 1559.

Porter, M.J.R., Duncan, N., Handeland, S.O., Stefansson, O., Bromage, N.R., 2001. Temperature, light intensity

and plasma melatonin levels in juvenile Atlantic salmon. J. Fish Biol. 58, 431438.

Purchase, C.F., Boyce, D.L., Brown, J.A., 2000. Growth and survival of juvenile flounderPleuronectes ferru-gineus (Storer) under different photoperiods. Aquac. Res. 31, 547 552.

Ridha, M.T., Cruz, E.M., 2000. Effect of light intensity and photoperiod on Nile tilapia Oreochromis niloticus.

Aquac. Res. 31, 609617.

Ross, L.G., McKinney, R.W., 1988. Photoperiod mediated variation in respiratory rate ofOreochromis niloticus

and its implication for tilapia culture. In: Pullin, R.S.V., Bhukaswan, T., Tonguthai, K., Maclean, J.L. (Eds.),

The 2nd Int. Symp. on Tilapia in Aquaculture. Bangkok, Thailand. ICLARM Conf. Proc., vol. 15. Interna-

tional Center for Living Aquatic Resources Management, Manila, Philippines, pp. 421428.

Saunders, R.L., Henderson, E.B., Harmon, P.R., 1985. Effects of photoperiod on juvenile growth and smolting of

Atlantic salmon and subsequent survival and growth in sea cages. Aquaculture 45, 55 66.

Silva-Garcia, A.J., 1996. Growth of juvenile gilthead seabraem (Sparus auratus L.) reared under different

photoperiod regimes. Isr. J. Aquac.-Bamidgeh 48, 84 93.

Siraj, S.S., Kamaruddin, Z., Satar, M.K.A., Kamarudin, M.S., 1988. Effects of feeding frequency on growth food

conversion and survival of red tilapia (Oreochromis mossambicus/O. niloticus) hybrid fry. In: Pullin, R.S.V.,



10/10

Bhukaswan T., Tonguthai, K., Maclean, J.L. (Eds.), The 2nd Int. Symp. On Tilapia in Aquaculture. Bangkok,

Thailand. ICLARM Conf. Proc., vol. 15. International Center for Living Aquatic Resources Management,

Manila, Philippines, pp. 383386.

Tandler, A., Helps, S., 1985. The effects of photoperiod and water exchange rate on growth and survival of

gilthead seabream (Sparus auratus, Linnaeus; Sparidae) from hatching to metamorphosis in mass rearing

systems. Aquaculture 48, 8182.

Toguyeni, A., Fauconneau, B., Boujard, T., Fostier, A., Kuhn, E.R., Mol, K.A., Baroiller, J.F., 1997. Feeding

behavior and food utilization in tilapia,Oreochromis niloticus: effects of sex ratio and relationship with the

endocrine status. Physiol. Behav. 62, 273279.

Trippel, E.A., Neil, S.R.E., 2002. Effect of photoperiod and light intensity on growth and activity of juvenile

haddock (Melanogrammus aeglefinus). Aquaculture 217, 633645.

Yousuf Haroon, A.K., Pittman, K.A., Blom, G., 1998. Diel feeding pattern and ration of two sizes of tilapia

Oreochromis spp. in pond and paddy field. Asian Fish. Sci. 4, 281301.

Zavyalov, A.P., Lavrovskii, V.V., 2001. Diurnal rhythms of feeding red tilapia Oreochromis niloticusO.

mossambicus reared in an apparatus with a closed cycle of water supply. J. Ichthyol. (Vopr. Ihtiol.) 41,

435441.


Documents

Effects of photoperiod on the performance of farmed Nile tilapia Oreochromis niloticus I. Growth, feed utilization efficiency and survival of fry and fingerlings.pdf