Ovulation induction in nase ( Chondrostoma nasus, Cyprinidae) using pituitary extract or GnRH analogue combined with domperidone

Abstract

Changes to the natural character of European streams as a result of human activities was followed by the dramatic decrease of nase ( Chondrostoma nasus, Cyprinidae) populations. Techniques of induced spawning would help culturists to increase hatchery production and supplement insufficient natural reproduction. Spawning experiments showed that the mean ovulation index (weight of stripped egg mass×100/weight of stripped egg mass+remnant ovaries) was high and similar in females receiving either pituitary injection at a dose of 6 mg/kg BW (86.2±5.9%; mean±SD) or 20 μg/kg body weight (BW) mGnRHa ([ d-Ala 6, Pro 9-NEt]-mGnRH) combined with 10 mg/kg BW dopamine receptor antagonist, domperidone (85.5±4.7%). Females receiving pituitary injection at lower dose of 3 mg/kg BW ovulated partially (ovulation index: 55.9±7.8%). The mean fertilization rate was significantly higher for the group receiving mGnRHa and domperidone injections (83.5±5.6%) than for the groups receiving pituitary injections at a dose of 3 mg/kg BW (69.1±3.7%) or 6 mg/kg BW (74.7±6.0%). These results might be attributed to the different nature of the hormonal treatments. No females ovulated in the group receiving 20 μg/kg BW mGnRHa alone indicating that in nase, similar to other cyprinids, there is a strong dopamine inhibitory tone on GtH secretion.