CEFAS Tilapia Workshop
18th June 2009
Institute of Aquaculture
Professor Brendan McAndrew
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,
Stirling strains widely used by
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
Single sex tilapia has been an ongoing research
MIXED SEX V’S MONOSEX TILAPIA
Mixed SexTilapia All Male Tilapia
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
Manipulation of sex-ratios in tilapia
• Hand sexing, 30g+ fish sexual dimorphism
• Hybridisation, Widely abused, niche use.
•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
Exogenous hormone swamps natural
hormone changes that cause sexual
Phenotypic change of sex the neomales or
neofemales produced are still the same
Simple highly efficient technique small
amounts of hormone applied for labile
EU regulation does not allow direct
application in human food chain.
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
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
START TIME HIGH RATE OF SEX REVERSAL
CONCENTRATION HIGH SURVIVAL RATE
F = Fertilisation; H = hatch; YSR = yolk sac resorption; SD = sexual differentiation
30-60ppm 17- α Methyltestosterone
Dose will depend on wide range of
parameters but must be started
before 10 days post hatch, swim-up
This require hatcheries to have tight
control over fry collection usually
egg-robbing and artificial incubation
to get the best % reversal.
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
Hormone never used in the production fish.
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)
Chromosome set manipulation
Induction of gynogenesis in fish
2nd meiosis 1st mitosis
oogonia duplication 1st meiosis 2n
1st polar body
YY male O. niloticus :
F0 XX female XY male
F1 MITOTIC GYNOGENESIS
XX female XY neofemale
r YY males
Progeny testing will identify neofemales
YY male production :
1st mitotic division
Mixed XX females and YY
Partial pedigree of androgenetic male O.niloticus and the % males in progeny
when crossed to normal females.
All-male Stirling red tilapia
Developed from pure Egyptian
Dominant red gene- no
melanophores in the epidermis.
Pure breeding strains available,
Androgenesis used to produce YY
males and can be supplied to
generate all-male fry in Stirling
This is the latest generation of Stirling red tilapia YY male
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
Useful technology for gene mapping.
Triploidy- not yet commercial reality.
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
Evidence from high %male lines that high
temperature can reduce this %.
Is this line worth pursuing?
Reproductive biology of tilapia
Hatchery production of
tilapia fry relatively inefficient
-need large numbers of
-hormonal control of
reproduction has not worked
-evidence that light is a major
cue and that tilapia respond
to day length and intensity
Female Nile tilapia from same family
ongrown under identical conditions to
Separated into four different light
regimes 6D:18L, 12D:12L, 18D:6L
Females maintained on these
regimes for 6 months and spawning
All eggs counted and measured.
Photoperiod control of reproduction
Number of Spawns Egg production
Total per month 6L:18D 12L12D 18L:6D 24L
6L:18D 12L:12D 18L:6D 24L Sep-01 Oct-01 Nov-01 Dic-01 Ene-02 Feb-02
Extended day lengths (18,24hr)
increased spawning activity –reduced
Inter Spawning Interval (ISI).
10 Highest and most consistent egg
5 product in 18hr day
6L:18D 12L:12D 18L:6D 24L
(Campos-Mendoza et al 2004)
Fecundity (x1000) Relative fecundity (egg/g) Longer days increased
8 relative and total fecundity
Number of eggs
1 b b a a
6L:18D 12L:12D 18L:6D 24L
1.2 Diameter mm Volume mm3
Shorter ISI resulted in more
y = 0.4405x + 0.2616 but smaller eggs
0.8 R2 = 0.3539; p 0.000
0.2 y = 0.1517x + 0.1938
R2 = 0.3202; p 0.000
(Campos-Mendoza et al 2004)
1 1.2 1.4 1.6 1.8 2
Log 10 ISI
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 Intensity - growth
Recent work has shown that growth
performance can be improved by using
continuous medium to low lighting
Up to 20% improvement in weight at 118
dph under experimental conditions needs
to be repeated under commercial
In other species benefits not seen until
later growth stages.
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
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.
Different photoperiod control systems
widely used in fish culture in NW Europe
to control sexual maturation and improve
growth performance in salmon, trout and
> 30% improvement on growth
performance with extended days.
Extended day-length in
hatchery likely to improve
Extended day-length in
ongrowing likely to
improve overall growth
rate –shorter production
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.
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.