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EFFECT OF DIFFERENT SALINITY LEVELS ON GROWTH AND SURVIVAL OF NILETILAPIA (OREOCHROMIS NILOTICUS)

K. J. Iqbal, N. A. Qureshi*, M. Ashraf, M. H. U. Rehman, N. Khan, A. Javid**, F. Abbas, M. M. H. Mushtaq***,F. Rasool and H. Majeed****

Department of Fisheries and Aquaculture, University of Veterinary and Animal Sciences, Lahore, Pakistan;*Department of Zoology, Government College University, Faisalabad

**Department of Wildlife and Ecology, University of Veterinary and Animal Sciences, Lahore.***Agro Visions, Faisalabad, Pakistan;

****Department of Biochemistry, Quaid-i-Azam University, Islamabad, PakistanCorresponding author email address: khaliduvas@yahoo.com

ABSTRACTA three months study was conducted in cemented tanks (2.896ft0.762ft0.914ft) to investigate the effect of differentsalinity levels on growth performance and survival of Nile tilapia (Oreochromis niloticus). Four salinity levels i.e. 1600ppm in Treatment 1 (TI), 2400 ppm in TII, 3200 ppm in TIII and 4000 ppm in TIV were maintained while in control (T0)the salinity level was 800 ppm. Each treatment was replicated thrice with 15 fish. Initial average body weight of tilapiawas 23.1 g 3.51 SD, 22.5 g 3.15 SD, 22.9 g 3.29 SD, 23.9 g 3.98 SD and 24.6 g 4.71 SD in T0, TI, TII, TIII andTIV, respectively. Fish were fed with 24.45% crude protein (CP) diet @ 4% of its wet body weight on daily basis. Bettergrowth rate was observed in TIV, food conversion ratio (FCR) was highest in TII while feed intake was poor in T0.Results indicate that the higher salinity (4000 ppm) levels have pronounced effect on fish growth which might be due toimproved osmoregulation. Temperature, electrical conductivity and pH showed positive correlation with growth whilethe same was negatively correlated with dissolved oxygen (DO). Fish weight and length were linearly correlated.Key words: Oreochromis niloticus, salinity, growth performance, survival, DO

INTRODUCTIONPakistan is located in tropical belt and a major

part of the country faces scarcity of rainfall. Hence duringsummer months country experience hot and dryenvironment. This results in excessive evaporation ofwater and buildup of salts in water reservoir (Ahmed,1993). This water deems unfit for not only agriculturecrops but also for majority of fishes. So it is extremelyimportant to find out possible alternatives for justifiedutilization of these abandoned water resources whereselection of suitable species is at the top (Mateen, 2007).Tilapia is one of the important fish species which hasseveral good qualities and can face wide range of salinityand other environmental conditions and can grow well inwater salinities ranging from 11 ppm to 29000 ppm,tolerate temperatures between 8 to 42 oC and can survivein low dissolved oxygen (DO) levels (0.1 ppm) (Pullinand McConnell, 1982).

The increasing market demand for tilapia andthe availability of vast brackish and sea water resourceshave led the introduction of this species at large scales.According to the Soil Survey of Pakistan (1985-1990),1.96 million hectares water is severely saline. This fishcan be an excellent candidate for culture in these waterresources. The objective of the present studies was

therefore to observe its growth performance, survival andhealth at different salinity levels.

MATERIALS AND METHODSThe fish were collected from fish production

ponds located at Ravi Campus University of Veterinaryand Animal Sciences, Pattoki. Fish was acclimatized inrectangular fish holding tanks in fish hatchery for threedays. There were four treatments and a control. Trial wasdesigned following Completely Randomized Design(CRD). All the treatments including control weretriplicated. Treatment; TI, TII, TIII and TIV had 1600,2400, 3200 and 4000 ppm salinity respectively whilecontrol was normal tube well water. The trials wereconducted in concrete tanks (2.896ft0.762ft0.914fteach; length x width x depth) for three months. All thetanks were randomly allotted to each treatment group insuch a way that each treatment would get three tanksinterspersed among the replicates of other treatments tocontrol systematic error. There were 15 fish in each tankand fish weight ranged from 15g to 35 g. Abovementioned salinity levels were maintained throughout theexperimental period by regular applications of sea saltfollowing its measurement by salinity meter (Condi 330i,WTW 82362 Weilheim Germany) to ensure the requiredsalinity level on daily basis. All the fishes measured and

The Journal of Animal & Plant Sciences, 22(4): 2012, Page: 919-922ISSN: 1018-7081

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weighed individually at the time of stocking. The 24.27% CP level diet formulated with inclusion of differentingredients (Table 1a), the complete composition ofdiet/ration is mentioned in Table 1b, this diet was offeredregularly @ 4% of fish wet body weight once a day.Physicochemical parameters like temperature anddissolved oxygen were measured by DO meter (YSI 55Incorporated, Yellow Springs, Ohio, 4387, USA),electrical conductivity and total dissolved solids bysalinity meter (Condi 330i, WTW 82362 WeilheimGermany) and pH was recorded by pH meter (LT-LutronpH-207 Taiwan) in the morning at 10:00 AM on dailybasis.

All the fish were harvested from each tank onweekly basis, weighed, measured and then released backin respective tank. Fish mortality was observed on dailybasis. The data collected from the successful completionof the trial were subjected to Analysis of Variance(ANOVA) using Minitab statistical package. Pearsoncorrelation method was used to compare and findinteraction effects between different parameters testedduring present study.

RESULTS AND DISCUSSIONThis study was conducted to investigate the

effect of different salinity levels (i.e. 800, 1600, 2400,3200 and 4000 ppm) hereafter called as control, T1, T2, T3and T4, respectively, on survival and growth of Niletilapia (Oreochromis niloticus) reared in cemented tank.

In present study better growth performance interms of average weight gain (g) and average length gain(cm) was seen in treatment containing highest salinitylevel (4000 ppm) while the lowest was observed incontrol group. Better food conversion ratio (FCR) wasfound in 1600 ppm salinity level and increased withincreased salinity levels. Feed intake was lowest at thelowest level of salinity i.e. 800 ppm and linearlyincreased with increasing levels of salinity (Table 2). It isaccepted that salinity is a key factor in controlling growthin tilapia that shows better performance in brackish water(Boeuf and Payan, 2001; Vonck et al., 1998). Sparks etal. (2003) reported that seawater (SW) rearing of tilapiaaccelerated its growth. Tilapia rendalli reared in thesalinity treatment of 10% showed improved growth thanthose reared in 5%, 15%, and freshwater (Kang'ombe andJoseph, 2008). According to Mena et al. (2002) growthrates among 25% and 35% salinities vs freshwater weresignificantly different, although no significant differenceswere observed in freshwater vs. 15% salinity.

Previously McElwee et al. (2002) had reportedfaster growth of tilapia (Oreochromis shiranus chilwae,O. shiranus chilwae and O. karongae) in 10 salinitywater declaring it a potential candidate for brackish wateraquaculture. Previous studies support ours and confirmthat higher salinities are quite favorable for the growth of

this species. Due to shortage fish was not tested in waterhaving salinity higher than 4000 ppm so it is not clear atthe moment whether this species will continue to grow atan accelerated pace in relation to increased salinitylevels. Ridha, 2008 had reported in his studies thatsalinity tolerance limits of this species are very muchrelated to its developmental stages and smaller fish ismore tolerant than bigger one but this phenomenon wasnot observed in current studies though there wassignificant and positive correlation between growth offish and salinity levels tested (Table 3). Studies of Altumand Sarihan, (2008) favorably corroborate with ourfindings who reported that salt tolerance of this groupdepends on species, strains and size, adaptation time andprevailing environmental factors.

In the present study salinity levels showedpositive and significant correlation with conductivity, pHwhile it showed negative significant correlation with DO(Table 3). Watanabe et al. (2007) observed that growthand survival in fish are not affected at different salinitylevels when temperature exceeds 27C but salinity haspronounced effect at temperatures below 25C.

In the present study, Nile tilapia reared atshowed 100% survival rate. Jamil et al., (2004) hadsimilar observation on tilapia reared at 0 ppm and 5000ppm. Contradictory to our and previous studiesKang'ombe and Joseph (2008) however observed thatsurvival rate of fish significantly varied with differentsalinity levels. Temperature negatively but significantlycorrelated with DO but was non significant withconductivity (Table 3). McElwee (2002) described thattemperature has an influence on salinity tolerance sincethey fluctuate together in nature and these fluctuationsmay positively or negatively influence growth andreproductive performance of cichlids. Jeremy et al.(1996) concluded that growth rate in juvenile Nile tilapia,Oreochromis niloticus is greatly influenced byfluctuations in temperature and salinity. Likongwe et al.(1996) found that feed conversion efficiencies andprotein efficiency ratios were highest at 32C and 8000ppm salinity and lowest at 28 C and 16000 ppm salinity.During present study, the conductivity showed significantrelationship with the growth parameters of the Nile tilapia(Oreochromis niloticus). Correlation of conductivity withpH, weight and length was found positive and significant.DO showed positive and non-significant correlation withpH, negatively significant with weight while negative andnon-significant with fish length (Table 3). Lei (2002)reported that oxygen consumption in Oreochromisniloticus and O. mossambicus varied significantly withvarying levels of salinity. El- Sherif and El-Feky (2009)observed that water pH 7-8 could be more suitable fortilapia culture for optimum growth performance andsurvival rate. The present study also revealed that pH hassignificant effect on the growth of Nile tilapia(Oreochromis niloticus) (Table 3). O. niloticus is more

Tari1Highlight

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Table 1a. Feed Formula of the Experimental DietSr. No. Ingredient Inclusion Level (%)

1 Fish meal 302 corn glutton meal 403 Rice Polish 294 Vitamin Premix 1

Total 100

Table 1b. Proximate Composition of the Experimental DietSr. No. Nutrient Percentage in Feed

1 Protein 24.272 Fat 4.153 Moisture 7.764 Fiber 11.975 Ash 13.846 Phosphorus 0.25

Table 2. Weight gain, length gain and feed conversion ratioTreatment (ppm) Average weight gain (g) Avg. length gain (cm) FCRControl (800) 28.000.69 b 2.30.07a 9.78

Treatment 1 (1600) 36.250.96 a 3.150.10 a 7.58Treatment 2 (2400) 36.401.42 a 3.550.12 a 7.88Treatment 3 (3200) 34.200.93 a 3.150.09 a 8.63Treatment 4 (4000) 36.651.30 a 3.70.11a 8.37

Superscripts alphabetic with similar letters in a column are statistically similarTable 3. Pearson correlation co-efficient matrix showing relationship of weight and length of Nile tilapia with

physico-chemical parameters studiedSalinity Temperature Conductivity DO PH Weight

Temperature -0.0750.399

- - - - -Conductivity 0.999

0.000-0.0480.585

- - - -DO -0.137

0.121-0.3510.000

-0.1480.094

- - -pH 0.321

0.0000.2130.015

0.3340.000

0.0060.947

- -Weight 0.394

0.0000.6280.000

0.4120.000

0.1550.078

0.2080.017

-Length 0.338

0.0000.6170.000

0.3560.000

0.0880.319

0.2370.007

0.9820.000

Test of significance at P20,000 ppm (Kirk, 1972). Our results indicatethat O. niloticus can survive and grow well at salinitiesup to 4000 ppm may be it can grow higher at highersalinities but it was not tested in current studies.Conclusion: It can be concluded that unlike other locallyculturable fish varieties it can comfortable live in 4000ppm salinity waters. It is further added that increase inpH has positive effects on its growth which is not true inother fish species.

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