Induced spawning and early ontogeny in hatchery-reared catfish Zungaro jahu (Siluriformes: Pimelodidae)

hatchery-kept catfish jahus zungaro jahu (ihering, 1898) were induced to spawn with carp pituitary extract. the telolecithal eggs were round (1.6 ± 0.1 mm in diameter), demersal, free, and covered with a 0.4 mm-thick jelly coat. the gonadosomatic index of 2.8 was comparable to that of other pimelodidae. the number of eggs x g of ova-1 was 804 ± 144. hatching occurred 14.5 h after fertilization, at a temperature of 27.3 ± 0.4o c. the newly-hatched embryos measured 3.9-4.3 mm of total length (tl). at 18 h post-hatching (hph; 5.3 ± 0.1 mm tl), the retina was pigmented, the mouth opened and dorsoflexion of the notochord had initiated. at 36 hph (6.4 ± 0.2 mm tl), fusiform chromatophores were vertically arranged in the primordial fin fold and the notochord was dorsoflexed. the yolk sac was almost exhausted by 48 hph (7.3 ± 0.2 mm tl). at 128 hph (8.6 ± 0.6 mm tl) the pectoral, dorsal, adipose, caudal, anal, and pelvic fins were readily observable whereas the primordial fin fold was no longer visible. at 224 hph (16.6 ± 2.5 mm tl), the metamorphosis was completed and the larvae had acquired the juvenile appearance.