Tilapia Research - Institute Of Aquaculture


Published on

By Dr Brendan McAndrew, Institute of Aquaculture.

1 Comment
No Downloads
Total views
On SlideShare
From Embeds
Number of Embeds
Embeds 0
No embeds

No notes for slide

Tilapia Research - Institute Of Aquaculture

  1. 1. CEFAS Tilapia Workshop 18th June 2009 Tilapia Research Institute of Aquaculture Professor Brendan McAndrew
  2. 2. Introduction  There has been research on tilapia undertaken at the IoA since 1978  Much of this early work funded by UK overseas development funds.  Wide range of subjects studied - genetics, nutrition, disease, reproductive biology.  Stirling strains widely used by industry
  3. 3. Background  Tilapia species gathered from wild in Africa.  All collections checked using morphological as well as genetic techniques to ensure purity.  Early work repeated existing studies to obtain baseline results on known genetic material – hybridisation both intentional and unintentional was widespread in commercial strains making identification difficult.  Single sex tilapia has been an ongoing research topic.
  4. 4. MIXED SEX V’S MONOSEX TILAPIA Mixed SexTilapia All Male Tilapia
  5. 5. TILAPIAS (Oreochrom is spp.) • Monosex male culture offers a solution to reproduction before harvest: this has been achieved by hormonal masculinisation or through genetic techniques • Sex determination appears to be largely genetic and monofactorial below about 34oC, but differs between species in the genus (O. niloticus and O. mossambicus XX/XY, O. aureus WZ/ZZ). YY males viable. • Above about 34oC, temperature affects sex ratio, largely through masculinisation of genetic females • No identification of sex chromosomes or sex-linked markers until recently - being developed at IOA
  6. 6. Manipulation of sex-ratios in tilapia • Hand sexing, 30g+ fish sexual dimorphism • Hybridisation, Widely abused, niche use. • Hormones •Hormonal sterilisation- unacceptable today. •Direct - larvae/fry are treated with steroid hormones during sexual differentiation to change sex ratio. •Indirect - sex determination system is manipulated in broodstock to result in progeny which are all genetically the same sex. • Temperature dependent sex-determination. 34-38 C can change phenotypic sex. female-male
  7. 7. Hormone sex-reversal  Exogenous hormone swamps natural hormone changes that cause sexual development.  Phenotypic change of sex the neomales or neofemales produced are still the same genetic sex.  Simple highly efficient technique small amounts of hormone applied for labile period.  EU regulation does not allow direct application in human food chain.
  8. 8. According to EU Directive 96/22/EC (entry into force 23 May 1996), • Contamination from substances with hormonal action and other substances. According to EU Directive 96/22/EC (entry into force 23 May 1996), Member States shall prohibit: (a) the placing on the market of stilbenes, stilbene derivatives, their salts and esters and thyrostatic substances for administering to animals of all species and (b) the placing on the market of betaagonists for administering to animals, the flesh and products of which are intended for human consumption. They shall, also, prohibit (i) the administering to a farm or aquaculture animal of substances having a thyrostatic, androgenic or gestagenic action and of betaagonists, (ii) the holding of animals on a farm, the placing on the market or slaughter for human consumption of farm animals or of aquaculture animals which contain the substances referred or in which the presence of such substances has been established, (iii) the placing on the market for human consumption of aquaculture animals to which substances have been administrated and of processed products derived from such animals,
  9. 9. HORMONAL SEX REVERSAL Labile period will vary depending on species 10 LABILE PERIOD days for tilapia 100 days for trout and seabass F H YSR SD DELIVERY HORMONE START TIME HIGH RATE OF SEX REVERSAL DURATION CONCENTRATION HIGH SURVIVAL RATE COMPETITION NATURAL FOOD F = Fertilisation; H = hatch; YSR = yolk sac resorption; SD = sexual differentiation
  10. 10. Direct treatment Dose between 30-60ppm 17- α Methyltestosterone (MT)  Dose will depend on wide range of parameters but must be started before 10 days post hatch, swim-up stage.  This require hatcheries to have tight control over fry collection usually egg-robbing and artificial incubation to get the best % reversal.
  11. 11. Indirect hormone treatment  This technique is normally used to generate a specific sex determination genotype.  In tilapia we want an all-male system in a heterogametic species. E.g. XY male XX female.  We need to develop YY males or ZZ females.  In fish there are several ways to achieve this result depending on the levels of sophistication available.  Hormone never used in the production fish.
  12. 12. Genetic all-male production in an XX/XY species – Nile tilapia using hormone treatments Process involves several labour intensive progeny (after Mair et al, 1991) testing stages.
  13. 13. Chromosome set manipulation Induction of gynogenesis in fish 2nd meiosis 1st mitosis genome 50% oogonia duplication 1st meiosis 2n replication 1st polar body 2nd pb n Fertilise with UV irradiated sperm 2n ovulation 100%
  14. 14. YY male O. niloticus : Mitotic Gynogenesis F0 XX female XY male DES F1 MITOTIC GYNOGENESIS XX female XY neofemale F2 P XX females r YY males o Progeny testing will identify neofemales g e
  15. 15. YY male production : Androgenesis FRESH SPERM Late shock 1st mitotic division Mixed XX females and YY males. Haploid embryos
  16. 16. Partial pedigree of androgenetic male O.niloticus and the % males in progeny when crossed to normal females.
  17. 17. All-male Stirling red tilapia  Developed from pure Egyptian O.niloticus.  Dominant red gene- no melanophores in the epidermis.  Pure breeding strains available, widely distributed.  Androgenesis used to produce YY males and can be supplied to generate all-male fry in Stirling strain.
  18. 18. This is the latest generation of Stirling red tilapia YY male
  19. 19. Chromosome set manipulations  Offer rapid way to generate new genotypes such as YY males.  Useful technology to study the inheritance of sex-determination mechanisms and other complex traits.  Useful technology for gene mapping.  Triploidy- not yet commercial reality.
  20. 20. Temperature sex-determination  Evidence that sex-ratio can be biased towards males by raising individuals from susceptible families at +34 C.  Selection for lines that produce a higher male % has shown improvements upto 90% male.  Evidence from high %male lines that high temperature can reduce this %.  Is this line worth pursuing?
  21. 21. Reproductive biology of tilapia Hatchery production of tilapia fry relatively inefficient -low fecundity -asynchronous spawning -need large numbers of females -hormonal control of reproduction has not worked -evidence that light is a major cue and that tilapia respond to day length and intensity
  22. 22. Photoperiod experiments  Female Nile tilapia from same family ongrown under identical conditions to maturity.  Separated into four different light regimes 6D:18L, 12D:12L, 18D:6L and 24L.  Females maintained on these regimes for 6 months and spawning activity monitored.  All eggs counted and measured.
  23. 23. Photoperiod control of reproduction in tilapia Number of Spawns Egg production Total per month 6L:18D 12L12D 18L:6D 24L 100 50000 80 40000 Spawns 60 30000 Eggs 40 20000 20 10000 0 0 6L:18D 12L:12D 18L:6D 24L Sep-01 Oct-01 Nov-01 Dic-01 Ene-02 Feb-02 Inter-spawning-interval Extended day lengths (18,24hr) 25 increased spawning activity –reduced 20 ab b Inter Spawning Interval (ISI). 15 ac days c 10 Highest and most consistent egg 5 product in 18hr day 0 6L:18D 12L:12D 18L:6D 24L (Campos-Mendoza et al 2004)
  24. 24. Photoperiod Fecundity Fecundity (x1000) Relative fecundity (egg/g) Longer days increased 8 relative and total fecundity 7 Number of eggs 6 a b 5 b b 4 3 2 1 b b a a 0 6L:18D 12L:12D 18L:6D 24L 1.2 Diameter mm Volume mm3 1 Shorter ISI resulted in more y = 0.4405x + 0.2616 but smaller eggs 0.8 R2 = 0.3539; p 0.000 0.6 Log10 mm 0.4 0.2 y = 0.1517x + 0.1938 R2 = 0.3202; p 0.000 0 (Campos-Mendoza et al 2004) 1 1.2 1.4 1.6 1.8 2 Log 10 ISI
  25. 25. Potential for photoperiod control  18L:6D produced 58% more eggs than the ambient 12L:12D photoperiod.  Fish under 18L:6D significantly higher total and relative fecundity, reduced ISI and greater clutch size.  Some photoperiod better than continuous light – entrain rhythm.  Further work on mechanism underway.  Evidence that they are very sensitive to light.
  26. 26. Light Intensity - growth  Recent work has shown that growth performance can be improved by using continuous medium to low lighting regimes.  Up to 20% improvement in weight at 118 dph under experimental conditions needs to be repeated under commercial conditions.  In other species benefits not seen until later growth stages.
  27. 27. Table 1. Light intensities in Watts m-2 and Lux (mean SE) measured at the bottom and surface of the tanks for each experimental treatment during day time. Treatment Watts m-2 Lux LL High top 3.0 0.2/ 684.0 32.0/ bottom 4.6 06 1031.0 104.0 LL Medium 0.5 0.1 / 141.5 17.5/ 0.7 0.1 172.5 10.5 LL Low 0.04 0.0/ 4.5 0.5/ 0.0 0.0 8.0 1.0 Control 0.7 0.1 / 172.5 22.5/ 0.9 0.2 190.5 30.5
  28. 28. Weight over time in Nile tilapia raised up to 118 days post hatch under different light intensities (High LL, Medium LL, Low LL and Control 12L:12D). Values are expressed as mean SE (n = 33-75 / replicate). Superscripts indicate significant differences between treatments at a given time point.
  29. 29. Different photoperiod control systems widely used in fish culture in NW Europe to control sexual maturation and improve growth performance in salmon, trout and marine species. > 30% improvement on growth performance with extended days.
  30. 30. Extended day-length in hatchery likely to improve fry yields. Extended day-length in ongrowing likely to improve overall growth rate –shorter production cycles. Genomic techniques being used at the moment to study many of the traits described- new developments to come New light technology used by cod farming operations in Norway and Scotland.
  31. 31. Scientists involved  Dr David Penman  Dr Hérve Migaud  Dr Jim Myers  Dr M. Gulam Hussain  Dr Antonio Campos-Mendosa  Dr Rafael Campos-Ramos  Dr Antonio Mendoza.  Dr Chris Martinez.