Spawning induction and embryonic development of Salminus hilarii (Characiformes: Characidae).

The present study aimed to evaluate two different methods of artificial reproduction induction, and characterize the embryonic development of Salminus hilarii. Different than observed for other tropical fish species, artificial reproduction induction followed by hand-stripping of gametes was considered unfeasible for S. hilarii, as no gamete fertilization was observed. However, females that were induced and spawned naturally presented a fertilization rate of 65.64 ± 0.54%. With a mean temperature of 26.20 ± 0.90ºC it was possible to clearly distinguish a large perivitelline space at 14 min after fertilization (AF) and at 49 min AF more than 50% of the embryos presented two blastomeres, and these cleavages occurred until 1 h 54 min AF. The gastrula phase was characterized at 3 h 56 min AF, and blastopore closure was observed at 8 h 31 min AF. At 9 h 1 min, organogenesis started, with a clear distinction of the yolk mass, embryonic axis, cephalic and caudal regions; at 11 h 51 min AF the embryos already had advanced segmentation and a free tail. Total hatching occurred at 21 h 17 min and after opening the mouth, which occurred at 33 h 9 min, the larvae of S. hilarii presented a strong and characteristic cannibalism. This information can be considered fundamental to improving S. hilarii production in captivity and for collaboration with a conservation programme in the upper Tietê river basin.