A new highly effective ovulating agent for fish reproduction. Practical application of LH-RH analogue for the induction of spawning of farm fishes.

The synthetic analogue of the nonapeptide LH-RH has been found to be highly effective in the induction of spawning of farm fishes (the grass carp, the silver carp, the spotted silver carp, and the black carp.) Its biological activity is many times higher than that of the synthetic decapeptide or natural releasing hormone. Out of a total number of 500 mature fishes treated with the nonapeptide alone and/or combined with a minimum amount of fish pituitary, 396 of them spawned--with an over-all spawning rate of 78%. As far as we know, this is probably the most effective ovulating agent or hormone now available for fishes. This finding is of paramount importance in pisciculture for large-scale production of fry. The recommended dosages for the following farm fishes are: the grass carp--1-10 microgram/kg b.w.; the silver carp--3 microgram or more/kg b.w. in divided doses; the spotted silver carp--1.4 microgram or more/kg b.w.; and the black carp--10 microgram/kg b.w. For the latter species, the efficacy of the peptide could be improved by a concurrent administration of 0.5-2 mg of the pituitary gland. The significance of this work in piscicultural practice and the mechanism of hormonal action are briefly discussed.