Tilapia is generic name of an African cichlids endemic group. This group is composed of three aquaculture of import sort of Oreochromis, Sarotherodon and Tilapia. Assorted features differentiate these three genera, but the chief critical concerns to reproductive behavior. All species of Tilapia are nesting in builders ; a brood parent guards the fertilized eggs in the nest. Both species of Sarotherodon and Oreochromis are talking brooders ; eggs gets fertilized in the nest but the parents immediately pick up those eggs in oral cavities and maintain them through incubation and for many yearss after hatching. Brooding in oral cavity is found merely in Oreochromis species, while in instance of Sarotherodon either male or both female and male are keeping incubators ( SRAC, 2005 ) .
During the last half of twentieth century fish husbandmans all over the tropical and semi-tropical universe have commenced agriculture Tilapia ( FAO, 2000 ) . Today, commercial production of of import Tilapia goes to genus Oreochromis beyond Africa, and more than 90 per centum of the farmed Tilapia are Nile tilapia outside of Africa. ( Balarin and Haller, 1982 ) reported that Nile Tilapia is the most popular Tilapia species for aquaculture and is widely distributed in many states other than native Africa.
Oreochromis niloticus is a rapidly turning species which can populate in assorted types of Waterss. It is highly adaptable and can utilize a broad scope of assorted nutrient beginnings ( along with workss ) , but feeds chiefly on phytoplankton along with benthal algae. Even though Nile Tilapia is assumed as a fresh water species it has shown a great border towards salt and can last in brackish state of affairss ( Beveridge et. al. , 2000 ) . Stickney et al. , ( 1979 ) reported that Nile Tilapia can digest to a broad scope of environmental conditions, fast growing rate, efficient to change over organic affair into high quality protein and have a favourable gustatory sensation.
2.1.3 Feeding Habits:
Tilapia has wide assortment nutrient beings that are natural, along with plankton, some aquatic benthal invertibrates, macrophyte, board quinine water and benthal larval fish, interrupting up organic affair, and debris. With heavy subsidiary eating, natural nutrient existences typically account for 30 to 50 per centum of growing of Tilapia. Tilapia is frequently referred as filter feeders as they can expeditiously harvest H2O plankton. The gills of Tilapia release a mucose which traps plankton. Then mucose rich with plankton or bolus, is swallowed ( EL-Sayed A.F.M. , 2006 ) .
Tilapia is an omnivore ; means provenders on both workss and animate beings nutrient beginnings. However, feeding behavior depends with size and age. Larvae normally feed on phytoplankton ( algae ) , fingerlings feed on zooplankton ( Artemia, moina, and rotifer ) , and while grownups consume both workss and carnal nutrient beginnings near the surface because are drifting feeders. In this respect, Caulton 1976 ; Saha and Dewan 1979 ; Brummett 1995 ; Turker et al. 2003 bumped that small Tilapia filtered well more phytoplankton sing than larger 1s. In add-on, Azim et Al. ( 2003 ) looked into effect of periphyton measure and size of fish ( 7 and 24 g ) on consumption rate by Nile Tilapia, and they observed that consumption rate between little fish significantly increased with denseness of periphyton, but non for fish with medium size.
2.1.4 Protein Requirements:
Including Tilapia Proteins are of import foods for all life beings for their construction and map. Continual usage of protein is being used for care, growing and reproduction. Therefore, uninterrupted supply of proteins or their constituent amino acids are necessary. Many surveies indicated that fish does non hold true protein necessity, but alternatively needs a good equilibrized mixture of dispensable and indispensable amino acids. Insufficient consumption of protein will ensue in deceleration of growing due to retreat of protein from fewer critical tissues to keep the map of critical parts. Excessively much supply of protein, nevertheless, merely portion will be used to synthesise new tissues and balance will be converted to energy ( NRC, 1983 ) .
Many findings have been carried out about the optimal dietetic protein degree for Tilapia. This degree for Tilapia appears to be influenced by size or age of the fish and ranges from 28 % to 50 % . For fry dietetic protein degrees runing from 36 to 50 % have been shown to bring forth best degree growing ( Davis and Stickney, 1978 ; Santiago and Laron, 1991 ; El-Sayed and Teshima, 1992 ) . That for juvenile 29 to 40 % has been determined to bring forth optimal growing ( Cruz and Laudencia, 1977 ; Teshima et al. , 1978 ) ; for immature grownup angle up to 40g 27.5 to 35 % appears to be maximal ( Jauncey and Ross, 1982 ; Siddiqui et al. , 1988 ; Wee and Tuan, 1988 ; Twibell and Brown, 1998 ) .
Practical diets for grow out of Tilapia normally contain 25 to 35 % petroleum protein. In pools, nevertheless, fish may hold entree to natural nutrient that is rich in protein, therefore dietetic protein degrees every bit low as 20 to 25 % have been estimated to be equal ( Newman et al. , 1979 ; Lovell, 1980 ; Wannigama et al. , 1985 ) .
Proteins are made up of amino acids. Arginine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine are the amino acids have been shown to be necessity for fish ( Moyle and Cech 1982 ) . The chief job is that measure for each type required differs from species, and inordinate measure might be damaging a fish ‘s wellness ( Moyle and Cech 1982 ) .
Scoliosis ( curvature of the spinal column ) can ensue due to miss of aminic acids in fish ( Moyle and Cech 1982 ) . Proteins are critical in the fish growing. Research has shown that due to certain proteins lack, growing will be scraggy. In the nature, omnivorous fish by and large feed on ample alive beings, protein enriched, that provide a valuable energy beginning ( Moyle and Cech 1982 ) . However, many commercial nutrients lack ample protein as it is expensive. Fish usage big sum of energy to oppress big and complex proteins. Due to this, saccharides and lipoids are replaced as energy beginnings ( Moyle and Cech 1982 ) .
2.1.5 Lipid demand:
On other manus, lipoids are found in tissues of both carnal and works and are digestible wholly ( Moyle and Cech 1982 ) . Symbiotic bacteriums are present in backbones of many herbivorous fish that helps to digest the saccharides and emancipate its energy to angle. Lipids supply higher energy than make saccharides, and besides render fatty acids, that are used for the energy building militias in fish. Predacious fish usually have a maximal growing rate due to their diet of unrecorded fish, which are of course high in lipoids ( Moyle and Cech 1982 ) .
Dietary lipoids are the chief beginning of indispensable fatty acids needed by fish for normal growing and development. They are critical bearers and aid in soaking up of vitamins with fat-soluble. Lipids, particularly phospholipids, are of import for cellular construction and care of membrane flexibleness and permeableness. Lipids serves as precursors of steroid endocrines and prostaglandins, better the spirit of diets and impact the diet texture and fatty acids composing of fish ( Webster I. et al. , 2002 ) . Takeuchi et Al. ( 1983 ) reported that indispensable fatty acerb demand of Nile Tilapia was found to be 0.5 % linoleic acid ( 18:2IZ6 ) .
2.1.6 Complete diets and Feeding Degrees:
Complete diets are of import in semi intensive civilization systems of Nile Tilapia, for a proviso of all indispensable foods to the fish. In order to develop such diets it is besides necessary to cognize the specific alimentary demands of the animate being and optimise provender preparation in order to obtain fast growing of high quality fish at low costs, ( Moore, 1985 ) .
2.1.7 Alimentary demand of auxiliary provender for Nile Tilapia:
Many surveies have been done to happen out the suited optimal alimentary degree for Tilapia. Fineman and Camacho ( 1991 ) observed that 30 % protein with 3500 kcal was better than 30 % protein with 3000 kcal for auxiliary provender for Oreochromis niloticus in brackish H2O pools. Watanabe et Al. ( 1990 ) found that concluding mean weight were high in 28 % protein to 32 % protein under all densenesss. Hanley ( 1990 ) found that increasing dietetic lipoid has no important consequence on growing rate, feed transition ratio and protein addition. De Silva and Perera ( 1985 ) and Siddiqui et Al. ( 1988 ) cited by Zonnveld and Fadholi ( 1991 ) found that optimal protein degrees for Fry and immature Nile Tilapia reared at maximal growing should be 28-30 % severally.
Table1. A Summary of the major food demands of Tilapia ( Jauncy and Ross. 1982 ) .
& gt ; 35
Table 2. Essential amino acids demands of immature Nile Tilapia ( Santiago and Lovell 1988 ) .
Requirements ( % protein )
Methionine +Cystine ( 0.54 % of the protein )
Phenylalanine + Tyrosine ( 1.79 % of the protein )
Table 3. Vitamin demand of Nile Tilapia for auxiliary provender.
Amount per kilogram in dry weight
Vitamin A activity
Vitamin D activity
Vitamin B 12
Beginning: National Research Council ( 1977 ) in Tacon 1979.
2.1.8 Water Quality Requirements:
Nile Tilapia would turn good in H2O with a temperature scope of 20-35A°c and optimal between 28A° and 30A°C and productiveness can be assumed at a upper limit within this temperature scope ( Ballarin and Haller, 1982 ) . Tilapia can non last at a temperature below 10A°c for more than few yearss. When it exposed to cold H2O, disease opposition is impaired and decease may ensue in merely few yearss ( Lovell, 1989 )
The tolerance degree of DO for Nile Tilapia is every bit lower as 0.1 mg/L ( Magid and Babiker, 1975 ) . Chevrvinski ( 1982 ) reported that O. niloticus could last by utilizing atmospheric O when morning DO concentration drops to less than 1 mg/L. Colt ( 1987 ) demonstrated that Nile Tilapia growing reduces as DO degree reaches below 5mg/L.. However, its survival depends on the continuance of low dissolved O in the civilization system. In armored combat vehicles, fish survive at the O degree of 1.2 mg/L by quaffing O from the ambiance for up to 36 hours if other H2O quality parametric quantities remain at an optimal degree ( Balarin and Haller, 1982 ) . Nile Tilapia has a deadly pH bound at about 4 and 11 severally and pH between 6.5 and 9 is the desirable scope for fish civilization ( Swingle, 1969 )
Nile Tilapia is more tolerant of high ammonium hydroxides level than any other species of fish. The deadly ammonium hydroxide degree for Tilapia is 2.3 mg NH3-N/L. , but it was reported that by prolong exposure, it can digest degrees of up to 3.4 mg/L ( Stickney, 1985 ) . A degree of nonionized ammonium hydroxide above 0.5 mg/L frequence consequences in mortality when fish are farther stressed by low O, managing ( Ballarin and Haller, 1982 ) .
Nile Tilapia is non straight affected by alkalinity and tolerance degree every bit high as 700 to 3,000 mg/L CaCo3 ( Morgan, 1972 ) . A entire alkalinity scope of 20 – 400mg/L is considered satisfactory for most aquaculture intent ( Tucker and Robinson, 1990 cited by Lawson, 1995 ) .
2.1.9 Phosphorous demand
The dietetic demand for P in tilapia varies from 0.9 % ( Watanabe et al. , 1980 ) , 0.45-0.6 % ( Viola and Arieli, 1983 ) , 0.3-0.5 % ( Robinson et al 1984, Robinson et al. , 1987 ) to 0.46 % ( Haylor et al. , 1988 ) depending on species, fish size, nutrient composing or look of a reported demand, available or concluding dietary P. The diet incorporating the complete mineral premix contained 0.9 % entire P, whereas the imbalanced Ca and P diet contained 0.5 % overall P.
Although fish could partially absorb P from its environment ( Lall, 1979, Lall, 1989, Lall, 19911, dissolved P is normally at really low degrees of about 0.005-0.05 Mg/L, which is unequal to run into their demand ( Nose and Arai, 1979 cited in Lall, 1991 ) . Hepher ( 1954 ) ( as cited in Hepher and Sandbank, 1984 ) noted that even in fish pools fertilized with phosphates, the degree of P does non increase much above its normal low degree due to absorption to dirty colloid and precipitation as indissoluble compounds.
Phosphorus is a constituent of phosphoproteins, nucleic acids and phospholipids, which play of import functions in energy metamorphosis. Addition of dietetic P has been reported to diminish the lipid content of musculus and entrails, whereas musculus protein content increased ( Murakami, 1970 cited in Lall, 1979 ; Takeuchi and Nakazoe, 1981 cited in Viola et al. , 1986 ; Shu, 1987 ; Hung, 1989 ; Wee and Shu, 1989 ) .
2.1.10 Calcium demand
The demand for Ca in Tilapia reared in calcium-free H2O was found to be 0.65 % for 0. areus ( Robinson et al. , 1984, Robinson et al. , 1987 ) . In the Ca and P uncomplemented diet, the Ca degree was approximately 1 % . At this degree, even without supplementation, it appears that the Ca degree in the soybean-based diet would be sufficient to run into the demand. The handiness of dietetic Ca to angle has non been studied. Furthermore, under normal conditions, one can non show a Ca demand in fish ( Cowey and Sargent, 1979 ; Robinson et al. , 1984, Robinson et al. , 1987 ; Yarzhombed and Bekina, 1987 ) because of Ca consumption from the H2O ( Dabrowska et al. , 1989 ; Luquet, 1991 ) .
In Nile Tilapia, Ca consumption takes topographic point in the tegument, peculiarly by the opercular membrane ( McCormick et al. , 1992 ) . In contrast to phosphorus, it seemed, hence, that the Ca demand could be met from the raising H2O. Activities such as liming of pools are likely beginnings of Ca. The similarity of Ca degrees in the concluding carcase of fish fed the Ca supplemented, calcium non-supplemented diets and the non-fed fish further support the likelihood of Ca consumption.
The Ca is a must in the fish diet for equilibrating the Ca and P ratio. Keeping an optimal Calcium and Phosphorus ratio is of import in diets for ruddy sea bream, eels, and creek trout but non for catfish, carp, and rainbow trout ( NRC, 1973, NRC, 1983 ; Ogino and Takeda, 1976 ; Viola et al. , 1986 ; Hepher, 1988 ; Lall, 1991 ) . In Tilapia, the function of the Ca: P ratio is non good defined and virtues further survey ( Robinson et al. 1987 ) . However, noted that in fresh water fish, dietetic Calcium: P ratio does non by and large impair growing or tissue concentration every bit long as dietary P is equal and Ca is present in the raising H2O.
2.2 Feeding criterions of auxiliary provender for Nile Tilapia
This is a set of tabular arraies, which include the measure of each dietetic constituent required for each age and species of fish for different degrees of production and care. When complemented by tabular arraies of provenders composing, so it is possible to explicate accurate rations for single or fish groups, an indispensable procedure for a least-cost ration feeding plan operation. Marek ( 1975 ) composed a feeding chart of common carp and Tilapia. The chart was holding appraisal of natural nutrient in the pool and subtracted from the deliberate provender demands for care and expected growing. The charts are based on the weight of fish, and alterations are adjusted harmonizing to the day-to-day growing of fish. In most instances, therefore ration is fixed for a longer period of clip ( Hepher, 1982 ) .
2.2.1 Feeding rate of Nile Tilapia
Underfeeding of fish can ensue in production loss. Overfeeding will do a dearly-won provender wastage and a possible cause of H2O pollution in add-on, a status resulting loss of animate beings or necessitating expensive disciplinary steps. Hence, both overfeeding every bit good as under-feeding has serious economic effects that affect the farm viability. Bard et Al ( 1976 ) stated that most of the supplemented provender is non to the full eaten by fish ; some bead to the underside of the H2O contributes to development of phytoplankton, hence advancing growing of fish both direct and indirect manner.
Sometimes a obscure direction might be read, like ‘feed 5 % of biomass per twenty-four hours ‘ as a dry provender. This might be applied during whole turning rhythm. This would most likely consequence in close starvation in the early phases and gross inordinate eating and subsequently H2O quality jobs. Feeding rates must non be steady throughout the whole of the growing rhythm boulder clay table size. They must be changed harmonizing to the fish age and its size to conditions of H2O. Brown et Al ( 1979 ) demonstrated that it is wasteful to equilibrate diets fed to angle in pools harmonizing to the absolute alimentary demand of the fish.
2.2.2 Stocking denseness and size
Feeding degree of fish in the semi intensive system increases with the addition of denseness of fish. As t denseness of fish in the semi intensive civilization additions per unit country, the nutrient demand of fish besides increases. This addition of biomass does non associate with the addition of natural nutrient and in many instances is associated with a lessening in the production of nutrient from nature due to limited supply to the overgrowing biomass stated ( 1979 ) that when the biomass of fish increased, each fish gets a smaller sum of natural nutrient, which may non run into its nutrition demand. This shortage can be covered by auxiliary provender.
2.3 Natural Food in a semi intensive civilization
Algae or “ phytoplankton ” is an microscopic weeds form the base of the fish nutrient concatenation. Adequate temperature, sunshine, and foods are basic for all green workss needed for growing. In presence of the sufficient visible radiation and proper temperature, chemical fertilisers ( N, phosphoric and K ) foods are readily assimilated by phytoplankton and increasing their copiousness. Manure comprises the same foods, is released and present to phytoplankton during and after decomposition. As phytoplankton absorbs fertiliser foods and reproduces to make heavy communities pond H2O alterations to brownish or greenish colour. This is known as phytoplankton bloom.
There are three basic feeding tracts by which input of fertiliser in the pool provides nutrition for fish:
Direct ingestion of organic affair by fish
Autotrophic productiveness of algae pursuant to fertilisation and their ingestion by filter feeding fish.
Heterotrophic productiveness of micro beings and benthal micro beings from manure inputs and their consecutive ingestion by fish.
These three BASICs feeding tracts can run in a individual aquaculture system, even though their comparative importance still a topic of intense argument Colman and Edwards, ( 1987 ) . In Israel experimental work reported that the heterotrophic tract of organic manure was found to be more efficient than an autophytic tract, Schroeder ( 1980 ) . It was stated that low fish production by an autophytic nutrient concatenation was due to the sunlight restrictions of phytoplankton with filter feeding fish chiefly depend on heterotrophic beings that are non light dependant. Therefore, the autophytic nutrient concatenation is required to supply the necessary DO which bound to the heterotrophic provender concatenation Colman and Edwards, ( 1987 ) .
The fertilized pools with foods stimulate the microscopic workss growing in the H2O ( phytoplankton ) . Phytoplankton is nutrient for other H2O animals ( zooplankton and larger animate beings ) that fish eat. Water becomes turbid or light-green colour ( called a “ bloom ) Martin et Al ( 1999 ) because of abundant growing of microscopic workss. Evaluation of the nutritionary value of natural nutrient is a hard because each fish species has its ain nutrition demand from its diet Determination of biomass of phytoplankton, zooplankton and benthic division in the fish pool must be related to the nutrient demand of fishes. Until now, there is non a dependable method developed for finding of secondary production, although primary production can be estimated. Spataru et Al ( 1979 ) reported that auxiliary provender can replace some of the natural nutrient. Aquino and Neilso ( 1982 ) supported that Oreochromis niloticus grow good in coops on nutrient.
The primary manufacturers ‘ which are sourcing of nutrient to different type of fish are non digested every bit by fish. Blue green algae Anabaena, Microcystis, Oscillator was reported to be indigestible because they have voluminous moulage, cellulose wall, or house periblast, ( Zhang, 1989 ) . Recent research work in China indicated that Tilapia can digest green-algae ( Zhang, 1989 ) .
Mellamena, ( 1990 ) reported that algae contain protein, fat, Carbohydrates varies 22 % to 48 % , 2 % to 16 % , and 14 % to 24 % severally. Zooplankton has more protein and fat content than any other phytoplankton except one gabber. Diatoms which have the more siliceous cell wall contain higher measures of inorganic affair. Tamiya, ( 1975 ) found that the mean protein content of algae is about 50 % on a dry affair footing. The biological value of algae is about 81.5 % significance that 124gram of algal protein corresponds to 100 gms of egg protein. The amino acerb composing of algae is similar to that of FAO mention protein except, there is a little lack in cystine and methionine as shown in the tabular array 4.
Table 4. Amino Acid profile of different algae ( g/kg N ) .
Beginning: Becker, 1990
* Amino acid lack
Lipids found in phytoplankton are typical ester of glycerin and fatty acids holding a C figure from C14 to C20. The major acids in diatoms are palmitic ( 16:0 ) , hexadecanoic ( 16:1 ) , Becker ( 1989 ) . Blue green algae have a larger sum of polyunsaturated fats ( 25 % to 68 % ) oftotaltriglyceride up to 80 % of the totalalgae lipoids. Lipid content of Cyanobacteria and green algaein out-of-door mass civilization is 7 % to 15 % lipoids ( Becker, 1989 ) . ( Nostocsp. , Calothrex sp. , Oscallaria and Spirulina sp. , Urenima sp. ) and 20 % to 25 % lipoids in green algae ( Scenedesmus ) , to 10 % in dry weight.
Table 5. Mineral Composition of some common fresh H2O micro algae in Percentage.
Beginning: Becker, 1986
All plankton feeders ‘ fish reported to digest diatoms such as Silver carp and Tilapia ( Power, 1960, 1966 ) . Tilapia zillii in Israel revealed that it had a capacity to disintegrate after gelatinlike matrix settlements of bluish green algae, particularly Microcystis ( Spataru, 1978 ) .