Hormonally Induced Ovulation of Northern Pike via Sustained-Release Vehicles

Although ovulation in northern pike Esox lucius can be induced by injections of dried fish pituitary-in-saline solutions, incomplete ovulation and low fertilization rates limit large-scale production of fry. The pituitary treatment was modified by using sustained-release vehicles, a hydrophilic biodegradable matrix of carboxymethylcellulose sodium (CMC-Na) and a Carbopol resin. Administration of carp pituitary in an 8.0% solution of CMC-Na or in a 2.0% aqueous dispersion of Carbopol resin produced a higher mean fecundity index and improved fertilization rate than pituitary injected in saline in some trials. The results suggest that, in northern pike, the rate of increase of the ovulation-inducing hormone may influence the relative quantity and fertilization rate of the ovulated eggs. Thus, modification in hormone administration may improve induced breeding techniques for this species.