Gonadotropin releasing hormone (GnRH) is now
the best available biotechnological tool for the induced
breeding of fish. GnRH is the key regulator and central
initiator of reproductive cascade in all vertebrates. It was
first isolated from pig and sheep hypothalami with the
ability to induce pituitary release of luteinising hormone
(LH) and follicle stimulating hormone (FSH). Since then
only one form of GnRH has been identified in most
placental mammals including human beings as the sole
neuropeptide causing the release of LH and FSH.
However, in non mammalian species (except guinea pig)
twelve GnRH variants have now been structurally
elucidated, among them seven or eight different forms
have been isolated from fish species (Halder et al.,
1991). The most recent GnRH purified and
characterized was by Carolsfeld et al. (2000). Depending
on the structural variant and their biological activities,
number of chemical analogues has seen prepared and
one of them is salmon GnRH analogue profusely used
now in fish breeding and marked commercially under
the name of Ovaprim throughout the world. The
induced breeding of fish is now successfully achieved by
development of GnRH technology (Bhattacharya et al.,
2002; Trivesh S.Mayekar et al., 2013).