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The fundamentals of producing monosex fish for aquaculture. D.J.Martin-Robichaud and Tillmann Benfey. Monosex stocks of various finfish are commercially produced in Canada Salmonids primarily, recently Atlantic halibut (Scotian Halibut Ltd) and research now on Atlantic cod
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and Tillmann Benfey
SEXUALLY UNDIFFERENTIATED FISH
ALL- FEMALE STOCK
B) INDIRECT FEMINIZATION. FEMALE HOMOGAMETY
(a) retain 2nd polar body (final product of meiosis)
(b) not affect survival
(a) activate eggs with UV-treated sperm
(b) 5 min @ 9500 psi, 15 min post-activation
Sufficient numbers of gynogens only need to be produced once to determine the sex ratio
(9 mo, 7 cm)
(21 mo, 25 cm)
Gynogen halibut 100% females =
females are the homogametic (XX) sex
to produce all-female Atlantic halibut stocks
but phenotypic male
Hormonal sex reversal
FEMALESteroid hormones and sex differentiation
The key steroids for gonadal differentiation in teleost fishes are
The critical enzymes in the synthesis of these compounds are
P450 aromatase and
Species specific labile period
Some species temperature (ESD) etc
influence gonadal development, or combination
(histology of 338 fish, 0.8 – 23.0 cm)
A 1.0 cm (hatch): germ cells appear
B 2.1 cm (end of yolk-sac stage):
primordial gonad apparent
C 3.8 cm (post-metamorphosis):
ovarian cavity formed
D 5.0 cm: oogonia apparent
Therefore the ‘labile’ period (i.e., hormonal sex reversal possible)
(a) cause genetic females to develop into functional males
(b) not affect fertilization ability
(a) 17α-methyldihydrotestosterone at 1mg/kg in dry feed
Hendry, C.I., D.J. Martin-Robichaud & T.J. Benfey. 2003. Hormonal sex reversal
of Atlantic halibut (Hippoglossus hippoglossus). Aquaculture 219: 769-781.
Which are neomales (genotypic females) and which are genotypic males.
Sex offspring produced by each male.
Sex-reversed females (XX) will produce 100% female offspring.
Chris Hendry, Harald Tvedt
Mike Reith, Tim Jackson, Darrin Reid
Scotian Halibut Ltd
NSERC, Aquanet, ACRDP
1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008
Hormonal regulation of sex differentiation
Genotypic: “Master” gene (e.g., dmy), minor sex determining
genes, autosomal genes
Sex differentatiation involves similar
or the same players across vertebrates, with the steroidogenic enzyme aromatase and the transcription factor dmrt1
playing a central role
Germ cell proliferation
Entry into meiosis
F. Piferrer & Y. Guiguen (2008). Fish Gonadogenesis. Part 2. Molecular Biology and Genomics of Sex Differentiation. Rev. Fish Sci., 16 (S1): 33-53.
The Future Prospects for Aquaculture Breeding in Europe. Professional and Scientific Workshop. Paris, October 1-3, 2008.
- Increased size dispersion and thus more need for size-gradings
- Less produced biomass within a given production unit
- Lower product quality if one sex is more valuable than the other
- Precocious maturation brings several additional problems to fish farming
- Depreciated product when release of sperm
Species for which one sex is more valuable and why
- Trout – maturation, flesh quality
- Sea bass – highly skewed sex ratios, precocious maturation
- Senegalese sole – highly skewed sex ratios
- Turbot – highest sex-related growth differences in favor of females
- Sturgeons – only females for caviar production
- Tilapias – males are usually larger than females
- Trout, Sea bass, Sea bream, etc. – Only female triploids do not develop gonads
Rainbow Trout (France, Scotland, Japan)
Brown Trout (France)
Atlantic Salmon (Canada)
Coho Salmon (Canada, Japan)
Amago Salmon and Masu Salmon (Japan)
Ayu and Hirame (Japan)
Channel Catfish (USA)
Nile Tilapia (China, Fiji, Philippines,
Thailand, USA, Vietnam)
Jordan tilapia (Israel)
Silver Barb (Thailand)
Scottish Rainbow Trout Production
Information provided by
Dr. B. McAndrew,
Univ. Stirling, Scotland
Hulata, G. (2001). Genetica, 111: 155-173.
Females on average ~750 g larger than males at Nov-08 sampling.