Notes on the induced reproduction and development of the tigerfish,Hydrocynus vittatus (Characidae), embryos and larvae

Synopsis In South Africa, the distributional range of tigerfish,Hydrocynus vittatus, has diminished over the past fifty years mainly as a result of migration barriers and reduced river flow. A project to restock traditional tigerfish waters has been envisaged for many years but did not materialise due to an inability to spawn this species artificially. Several hormones were therefore tested for their potency to induce ovulation in this species. Gonadotropin releasing hormones (GnRh) were used in combination with dopamine receptor antagonists. Human chorionic gonadotropin (HCG) was administered in conjunction with catfish pituitary gonadotropin. Both sexes were successfully stripped and the eggs were inseminated artificially. Tigerfish eggs are small (0.65 mm diameter), demersal and slightly adhesive. Hatching occurs 22 h 30 min after insemination and free embryos are pelagic and display continuous vertical movement for a period of three days. Embryonic development was photographed until first feeding, 5 days after hatching. From these results as well as field observations, it is concluded that tigerfish spawns on a sandy substrate in the vicinity of aquatic vegetation.