Sex Control of Fish

Sex control is the technique to produce desired sex by various ways. The species achieved faster growth rate with better FCR. These are economically important and prolific breeding or over crowding due to prolific breeding can be avoided. The methods are as follows –

Feminisation ----------------- Hormonal treatment
----------------- Back cross with sex reversed male and normal female

Masculization ---------------- Hormonal Treatment

Contracept ---------------------- Drugs/Chemicals/Hormones

Sterilisation -------------------- Drugs/Chemicals/Hormones
-------------------- Hormonal Treatment
--------------------- Heat & Cold Shock/Pressure Shock
--------------------- X-ray

The role of Hormones in sex reversal –

Sex reversal has been achieved by hormonal control methods. The hormone which is used in feminisation is estradiol – 17-ß, ethyl estradiol. The hormones are used in early maturation stages administered by food and the undifferentiated gonads are transferred to the female ovary. Dose and treatment period is specific to the single species as for example 20g estradiol is used per kg of food, with 120 days treatment period for salmon fry for 100% feminisation. The female hormone which is use in early developmental stages in male fishes can change the male to female phenotypically, but genetically it would be XY.

For synthetic hormone oestrogen, one has to take care and should avoid high level of dose because it may cause liver damage and mortality of fry.

In case of masculisation the 17-α Methyl testosterone is used in early maturation period of fish. It can convert the female fish into male fish phenotypically, but genetically it would be XX. Generally much higher dose of androgen can be used in two ways – I. by food, II. Bathing of larvae in hormone treated water. In case of salmon fry the dose of hormone in food is about 3mg/kg and for Tilapia it is 20-30mg/kg of food. The androgen is also growth stimulating hormone.