This research was conducted in the middle basin of the Putumayo River from November 2020 to October 2021. The objective of the work was to establish the reproductive biology of Potamorhina altamazonica "llambina" and Prochilodus nigricans "boquichico" in their natural environment. Sampling was carried out through records of fishing landings from different ports, collection centers and through exploratory fishing activities in fishing areas near the town of El Estrecho (02°26'29.9" S, 72°40'11.3" W). A total of 336 llambinas and 253 boquichicos, were analyzed for a period of 12 months, collecting data in the early morning hours (4:30 a.m. and 8:30 a.m.), while monitoring of the lakes was carried out between 17:00 pm and 6:00 am. Biometric data (LS, LH, LT and weight) were recorded for both species, followed by the recognition of the gonads by direct observation, which followed the metho...