Ovulation inducement in prespawning adult Danube salmon (Hucho hucho, L.) by injection of acetone-dried carp pituitary (cP)

In order to obtain simultaneous ovulation of all Danube salmon females within a hatching stock, i.e. of those fish kept in hatchery ponds for several years as well as of those recently collected in rivers, injection of carp pituitary (cP) was attempted. Total doses of 4 mg cP/kg body weight administered in a single application induced ovulation after 98 to 210 h. Application of two subsequent doses (a pre-injection of 10% followed by a post-injection of 90% after 12 h) resulted in a better synchronized ovulation 142 to 162 h after the first injection. Further consequences of injecting two seperate cP doses were easier egg stripping, higher fertilization rates of the eggs and lower mortality during embryonic development. The possibility of a general application of cP for artificial breeding of Danube salmon is discussed.