TILAPIA

Originally native of Africa but distributed all over the world

1. Easy growing fish , reproduces prolifically under natural conditions

2. Remarkable ability to adapt to different climatic regions of the world- salinities, foods and ecosystems

3. Sometimes undergo precocious sexual maturation under adverse conditions

4. Highly disease resistant.

5. Good growth rate and feed conversion efficiency.

6. Males exhibit faster growth rate compared to females.

GLOBAL AQUACULTURE PRODUCTION OF NILE TILAPIA (FAO)

China first in the production.

Oreochromis niloticus (Nile Tilapia) Aquatic chickenoMost favoured species for culture, originally found in Nile valley, upto Central and Western Africa.o7 sub species oGrows to more than 600 gms within 6 months and attains about 3kg wt and 50 cm length in wild.oMales exhibit 2.5 times the growth rate of females.oOmnivore, feeding on phytopl., and also on detritus and benthic fauna. oSalinity tolerance – upto 29 ppt.oTemp- below 12degrees is lethal.

Sexual Dimorphism- sexes separate

Male Female

•Two apertures on ventral side of belly Anus and urinogenital

•Urinogenital aperture smaller

•Three apertures- anus, urinary And genital aperture

•Bigger Urinogenital aperture

Age at first maturity -10 -17 cm length and 4-5 months

Courtship behaviour- Males show active display in their breeding territory –

called lek, Nests are prepared by scooping out depressions at pond bottom. Mature femaleVisits the pond and there is immediate courtship and mating.

Mature fish spawn 6-12 times in a year. The number of eggs in one batch – 100- 2000. Larger females produce more eggs per batch and eggs are larger in size.

Parental care Tilapia niloticus is a maternal mouth brooder Soon after fertilization the eggs are picked up by the female in its mouth for incubation. Then the female leaves the territory or lek.Incubation period varies from 4-10 days depending on temperature.At 20 Deg C - - 6daysAt 28 Deg C – 4 daysAt 30 Deg C- only 3 days.After hatching, larvae takes 4 to 6 days for yolk sac absorption. When fully absorbed , the larvae leave the mouth of the mother.- swim up fry- start feeding.Mother continues to shelter the larvae for 1-4 days more.Larvae takes 10-12 days to become fully independent.Mother does not feed during incubation but starts feeding vigorously when the period is over.

Eggs- large yolky , size of eggs vary according to the age of parent fish.

Oreochromis mossambicus (Java Tilapia)

•Widely cultured•Monogamous maternal mouth breeder•Sexual maturity at 2-3 months of age and 6-10 cms long.•Breed in shallow waters 30-90 cm•Males prepare the nest which are depressions of 35cm dia.•Female lays the eggs and are fertliised by the male.•75-100 eggs are taken into the mouth of the female. •Eggs hatch out witihin 2-5 days •larvae are retained in the mouth till the yolk sac is fully absorbed.•Offsprings when threatened return to the mouth of female for 10-15 days.•Female seldom eats during incubation time.•Breeds 6-11 times a year, once in every 22-40 days.•Breeds when temp. is 21-23 deg.C and when the temp lowers to 11-13 Deg.C it stops breeding.

Other Species of Tilapia

Oreochromis aureus, Oreochromis spilurus niger,

O.urolepis hornorum, O. macrochir, Sarotherodon galileus, S. melanotheron

Tilapia rendalli , T. zilli.

Problems in aquaculture of Tilapia Uncontrolled reproduction causes overpopulation – stunted growth, and uneconomic returns. Collection of naturally produced fry – not sustainable - cannibalism among the fry, older and larger consume the weaker fry. - Asynchronous breeding habit. - Overcrowding, stunted growth and decline in reproductive efficiency. - decline in frequency of spawning and reduced fecundity

Advanced techniques for brood stock management

1.Conditioning brood fish before spawning

a. Stocking the brood fish at optimum stocking density b. Providing the brood fish with good quality feed.c. O. mossambicus is reported to feed upto 40% of their body weightd. immediately after release of fry from its mouth.

2. Collecting the larvae from the mouth of the brood fish

a. Water level is lowered to 20-30 cm depth.b. Females are examined for presence of larvae c. Eggs are collected from the mouth into a basin. d. Eggs are taken for artificial incubation e.Spawned females are replaced by ready to spawn females once in 10 days

M3. Stripping of brood fish

a. Female fish can be stripped for obtaining eggs,b. Milt also collected in the same manner.

4. Artificial incubation of eggs Incubation device is a round bottom container (20 litre) with inlet pipe at the centre and an outlet pipe at the side

Can hold about 80000 eggs for incubation.

Outlet water is allowed to flow into a fry tray – collection of any hatchling that are carried out thru the overflowing water.

Water from the fry tray is allowed to flow into a filtration unit by gravity. The unit – prefilter, slow sand filter and UV steriliser.

Water is allowed to flow into a sump or reservoir

From sump water is pumped into an overhead tank from where the outlet pipe is connected to the incubation vessel.

Larval care in Tilapia culture

•Newly hatched larvae are delicate and reared in trays in a flow through system (Yolk sac absorption tray)

•Rearing continues for upto 20 days after hatching

•Tray made of Al or plastic 40X 25 X 8 cm or 40 X 30 X 10 cm with holes on lateral sides

•Fine meshed plastic or nylon net is fixed inside the tray, prevents the escape of the hatchlings when water flows through the tray

•A 3 cm water depth is maintained in the tray

•Faster the flow rate, the lesser time it takes for yolksac abspn.

•Fry after yolksac abspn – called swim fry start feeding, fed 4-8 times/day

PRODUCTION OF MONOSEX SEED OF TILAPIA

Hormonal sex reversal

Hybridisation

Tilapia farmers choose to raise male tilapia only since they have a higher growth rate compared to females

Hormonal sex reversalHormonal sex reversal

Newly hatched larvae are fed with hormones in the feed for 3- 4 weeks starting from 10 th day of hatching when the gonad is in the undifferentiated stage.

17 alpha methyl testosterone – hormone used for sex reversal17 alpha ethynyl testosterone is also used.

Feminisation of genetic male done thru oestrogen – these functional females when mated with genotypic males all male offsprings are produced.

HybridisationWhen certain species of Tilapia cross breed, the result will be an all male or all female population.

Male parent Female parent Offspring

O. aureus O. niloticus 100% male

O. Urolepis hornorum O. niloticus 100% male

O. macrochir O. niloticus 100% male

O. niloticus O. mossambicus 100% female

O. Urolepis hornorum O.aureus 100% female

Hybrids have been shown to possess hybrid vigour 1. Better growth rate, greater body depth and width2. Purity of parental stock has to be ascertained for producing single sex offsprings.