Ultrasonography as a non-invasive method for sex identification and spawning female selection in Neotropical catfishes

This study explored, for the first time, ultrasonography as a non-invasive tool for sex identification and selection of candidate spawning females in two Neotropical catfishes, Pseudopimelodus mangurus and Pimelodus maculatus. Broodstock were examined with a 7.5 MHz ultrasound transducer positioned in the ventral region. Ultrasound scans allowed clear differentiation between sexes and identification of mature ovaries during the reproductive season. Significant differences in body size and ovarian dimensions were observed between spawning and non-spawning females. Induced spawning was performed in 17 P. mangurus and 42 P. maculatus females, resulting in successful reproduction in 41.2% and 80.95%, respectively. P. mangurus showed higher fertilization (90.6%) and hatching rates (72.1%) than P. maculatus (76.5% and 39.0%, respectively). Although no significant correlations were detected in P. mangurus, ovary area was positively correlated with relative extruded weight in P. maculatus. Ultrasound images provided accurate ovarian assessment and highlighted morphological differences between species. The results confirm ultrasonography as a fast, safe, and effective method for sexing and selecting spawning females, avoiding invasive procedures, reducing handling stress, and preserving valuable broodfish. This technique offers a valuable alternative for broodstock management and conservation programs involving Neotropical catfishes.