Induced spawning and reproductive variables of the catfish Lophiosilurus alexandri Steindachner, 1876 (Siluriformes: Pseudopimelodidae)

Lophiosilurus alexandri is an endemic fish from the Sao Francisco River basin, Brazil. The aim of this study was to induce L. alexandri to spawn and to obtain data on several reproductive variables for this species. For induced spawning, adults were submitted to Cyprinus carpio pituitary homogenate (CPH). Nine of the 12 females (75%) responded positively to the treatment. The stripping of oocytes was performed 8.4 h after the second dose of CPH with the water temperature maintained at 26 degrees C. The number of stripped oocytes per gram of ova was 74 +/- 5 oocytes g(-1), and the mean oocyte diameter was 3.1 +/- 0.2 and 3.6 +/- 0.2 mm, before and after hydration, respectively. The oocytes were opaque, yellowish, demersal, highly adhesive, and covered by a gelatinous coat. The total fecundity was 4,534 +/- 671 oocytes, and the fertilization rate was 59%. The initial and final fertilities were 2,631 +/- 740 and 1,542 +/- 416 embryos, respectively. Larval hatching occurred up to 56 h after fertilization, and the larvae had a total length of 8.4 +/- 0.1 mm. This work provides important biological information for L. alexandri that can be used for management and conservation of this species.