Reproductive biology characterization of violinha Loricariichthys anus

This study aimed to characterize the reproductive biology of Loricariichthys anus (violinha) from the Guaíba River (Brazil) to support conservation efforts and development of captive reproduction protocols. Monthly collections (November 2021-October 2022) of 144 specimens were analyzed for sexual dimorphism, gonadosomatic index (GSI), gonadal histology, and sperm parameters (motility, concentration, morphology). Sexual dimorphism was evidenced by elongated lower lip in males, predominantly during the reproductive period (November-March). GSI values peaked during November-March for both sexes (P < 0.05). Histological analysis revealed females reached maturity from November to February with evidence of multiple spawning, while males produced sperm year-round, albeit in low volumes. Sperm motility parameters differed significantly between individuals (P < 0.05) with mean concentration of 6.88 × 106 ± 8.18 × 105 spermatozoa/mL. L. anus reproductive period occurs from November to February, with males presenting low seminal volume and viable sperm concentration compared to other Loricariidae species, which has implications for both conservation and captive reproduction efforts.