Hybridization of Fish

It is the technique of breeding of fishes between two species or genera which ordinarily do not breed.

Hybridisation in nature:

Most fishes release their eggs and sperms in water and fertilisation are external. Fish hybridizes more frequently than tetrapodes so fertilization of closely related species which leaves in same water bodies, are common. Reservoir is the most important area where natural hybridization occurs frequently than rivers, because the area is not too large as rivers and scarcity of certain species with preponderance of others. Naturally hybridized fishes are found in following families – Esocidae, Catastomidae, Cyprinidae, Salmonidae, Poecillidae etc of about 56 families.

Technique of Hybridization:

The hybridization is done actually by inducing the virgin fishes or small aged group fishes. The hybridized fish possess intermediate character of two species. This type of hybridization is also known as diploid hybridization. This hybridized fishes are capable to produce new fish up to F2 progeny. Inter specific and Inter generic both type of hybridization is done in India.

Inter specific hybridization – Inter specific hybrids are generally producing by mating between two different species in same genus. In India mating female kalbasu and Labeo rohita is highly successful. Over 94% fertilisation was obtained. The growth rates of hybrids are superior to the parent Kalbasu. It attains maturity in two years. The hybrids also can be bred by hypophysation and can be obtained F2 generation. However the fishes are selected by following process –

The brooders are selected in first maturity generally virgin.
One pair of males (rohu) and one pair of females are injected to induce them prior to breeding by hypophysation technique.
The breeders are kept separated for some times and then they are released in breeding hapa with suitable breeding conditions.

The inter generic hybridization – In this method male and female are generally selected from different genera and produced by above mentioned methods. In India, successful hybrids are as follows –

Parent ♂ Parent ♀ Hybrids
Catla catla Labeo rohita Rohu-Catla
Catla catla Labeo calbasu Catla-Kalbasu
Catla catla Cirrhinus mrigala Catla-Mrigal
Labeo rohita Cirrhinus mrigala Rohu-Mrigal

Inter generic hybrids between Catla and Rohu attains full maturity in 3yrs and they also be induced to breed. Crossing between Rohu and Mrigal is more successful and 90% fertilisation is done and hybrids attain full maturity in 2yrs and showed intermediate character. Mrigal-Kalbasu hybrids attain full maturity within 2-3yrs. These hybrids are also capable to produce new ones. These are –

Parent ♂ Parent ♀ Hybrids
Catla catla Mrigal-Kalbasu Catla-Mrigal-Kalbasu
Labeo calbasu Mrigal-Kalbasu Rohu-Mrigal-Kalbasu

These hybrids are matured within one year.