Attempts to induce an LH surge and ovulation in common carp (Cyprinus carpio L.) by differential application of a potent GnRH analogue, azagly-nafarelin, under laboratory, commercial hatchery, and natural conditions

Abstract

Abstract The study was performed in order to try to provoke the gonadotropin wave and ovulation in common carp using a potent GnRH analogue, azagly-nafarelin (AZAGLY), without the use of dopamine (DA) antagonists. Different doses, routes of delivery, and injection protocols were applied, as well as different experimental conditions (laboratory, hatchery, and natural). It has been shown that the best and the simplest way of AZAGLY administration was by intraperitoneal injection. Despite dose (40 or 80 μg/kg body weight) and number of injections (one or two), maximal plasma carp-luteinizing hormone (cLH) concentrations never exceeded 40–50 ng/ml. There was no priming effect on final plasma cLH concentrations. Using different treatment protocols, it was possible to obtain 40–60% ovulated females in laboratory as well as hatchery conditions. However, time of ovulation after AZAGLY treatment in some cases was less compressed in comparison with Ovopel-treated (a local commercial product, containing a GnRH analogue plus the dopamine antagonist, metoclopramide) fish. Egg quality was not altered by AZAGLY treatment. With natural spawning, in unfavourable thermal conditions, AZAGLY treatment induced spawning in a limited number of females. It is postulated that, if antidopaminergic drugs are ever banned from use in aquaculture, AZAGLY treatment alone can be considered as an alternative method of inducing ovulation in cyprinid fish for artificial spawning.